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European Journal of Inorganic Chemistry - Current Research Articles



Current research articles: Inorganic Chemistry

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European Journal of Inorganic Chemistry - published by Wiley-VCH

EurJIC is the fastest growing journal in inorganic chemistry. It publishes Full Papers, Short Communications, and Microreviews from the entire spectrum of inorganic, organometallic, bioinorganic, and solid-state chemistry.




Current articles of the journal:



Graphical Abstract: Eur. J. Inorg. Chem. 7/2015

Posted on 3 March 2015 | 1:41 pm


Hybrid Materials Engineering in Biology, Chemistry, and Physics

The Guest Editors emphasize the rapidly growing research in advanced materials. “Telecommunication, health and environment, energy and transportation, and sustainability are just a few examples where new materials have been key for technological advancement.” The Guest Editors emphasize the rapidly growing research in advanced materials. “Telecommunication, health and environment, energy and transportation, and sustainability are just a few examples where new materials have been key for technological advancement.”

Posted on 3 March 2015 | 1:41 pm


Constitutional Hybrid Materials – Toward Selection of Functions (Eur. J. Inorg. Chem. 7/2015)

The back cover picture shows constitutional hybrid materials composed of columnar silica mesopores used as a scaffolding matrix to orient ribbon-like macrocyclic systems, reversibly connected with the inorganic silica through hydrophobic non-covalent interactions. The dynamic character leads to reversible interactions between the non-grafted organic components and the inorganic hydrophobic silica matrix, making them respond to external ionic stimuli. Evidence has been presented that such systems adapt their internal structure and evolve so as to improve their ion-transport properties. Details are presented in the Microreview by M. Barboiu on p. 1112 ff.

Posted on 3 March 2015 | 1:41 pm


Hybrid Materials, the Materials for Today's Technology

Biomimetic ion channels, supported catalysis, metalorganic frameworks, layered double hydroxides and biomineralization are all examples of topics covered in this cluster issue, “Hybrid Materials: Next Generation in Chemistry, Physics and Biology”, presenting a wide variety of inorganic chemistry from synthesis and host–guest chemistry to applications in bioinorganic chemistry, catalysis and fuel cells. Biomimetic ion channels, supported catalysis, metalorganic frameworks, layered double hydroxides and biomineralization are all examples of topics covered in this cluster issue, “Hybrid Materials: Next Generation in Chemistry, Physics and Biology”, presenting a wide variety of inorganic chemistry from synthesis and host–guest chemistry to applications in bioinorganic chemistry, catalysis and fuel cells.

Posted on 3 March 2015 | 1:41 pm


Masthead: Eur. J. Inorg. Chem. 7/2015

Posted on 3 March 2015 | 1:41 pm


Furan-Modified Spherosilicates as Building Blocks for Self-Healing Materials

Invited for the cover of this issue is the group of Guido Kickelbick at Saarland University, Saarbrücken, Germany. The cover image shows the molecular building block that plays the major role in the self-healing processes of modern hybrid materials through crosslinking and de-crosslinking reactions. We wanted to investigate possible routes to incorporate self-healing properties into inorganic?organic hybrid materials...Read more about the story behind the cover in the Cover Profile and about the research itself on p. 1226 ff.

Posted on 3 March 2015 | 1:41 pm


Furan-Modified Spherosilicates as Building Blocks for Self-Healing Materials (Eur. J. Inorg. Chem. 7/2015)

The cover picture shows the molecular building block, which plays the major role in this type of material. The organically functionalized spherosilicate contains furanyl groups at all eight corners, which act as dienes in the Diels–Alder reaction. The synthesis of this inorganic building block is straightforward and it can be achieved easily in a multigram scale. The scheme below shows the principle of the crosslinking and de-crosslinking reaction in the material, which is a prerequisite for the self-healing cycles. In the background, a macroscopic self-healing process is shown by the disappearance of surface scratches, which is also presented in the paper. Details are discussed in the article by T. Engel and G. Kickelbick on p. 1226 ff. For more on the story behind the cover research, see the Cover Profile.

Posted on 3 March 2015 | 1:41 pm


Two-Dimensional Hybrid Materials: Transferring Technology from Biology to Society

Hybrid materials are at the forefront of modern research and technology; hence a large number of publications on hybrid materials has already appeared in the scientific literature. This essay focuses on the specifics and peculiarities of hybrid materials based on two-dimensional (2D) building blocks and confinements, for two reasons: (1) 2D materials have a very broad field of application, but they also illustrate many of the scientific challenges the community faces, both on a fundamental and an application level; (2) all authors of this essay are involved in research on 2D materials, but their perspective and vision of how the field will develop in the future and how it is possible to benefit from these new developments are rooted in very different scientific subfields. The current article will thus present a personal, yet quite broad, account of how hybrid materials, specifically 2D hybrid materials, will provide means to aid modern societies in fields as different as healthcare and energy. This essay focuses on the specifics and peculiarities of hybrid materials based on two-dimensional (2D) building blocks and confinements. It presents a personal, yet quite broad, account of how hybrid materials, specifically 2D hybrid materials, will provide means to aid modern societies in fields as different as healthcare and energy.

Posted on 3 March 2015 | 1:41 pm


CuPN2: Synthesis, Crystal Structure, and Electronic Properties

CuPN2 was successfully synthesized from Cu3N and P3N5 at 5 GPa and 1000 °C by employing the Walker-type multianvil technique. Its crystal structure was elucidated from powder X-ray diffraction data. CuPN2 is isostructural to LiPN2 and NaPN2 [tetragonal I$\bar {4}$2d, no. 122, a = 4.5029(2) Å, c = 7.6157(2) Å, V = 154.42(1) Å3, Rp = 1.303, wRp = 1.741] with a structure that can be derived from both chalcopyrite and zincblende type. The electronic structure of CuPN2 was investigated by means of DFT calculations. CuPN2 is an indirect semiconductor with a bandgap of 1.67 eV. CuPN2, the first known ternary Cu phosphorus nitride, has been synthesized under high-pressure high-temperature conditions. It is isostructural to LiPN2 and an indirect bandgap semiconductor as shown by DFT calculations.

Posted on 2 March 2015 | 12:10 pm


Theoretical Insight Into the Role of Triarylboron Substituents in Tetradentate Dianionic Bis(N-heterocyclic carbene) Platinum(II) Chelates – Improving the Performance of Blue Light Emission

The electronic structures and photophysical properties of eleven PtII complexes divided into three series by their degree of ? conjugation were studied through density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. To investigate the effect of triarylboron substituents and the changes caused by the extension of the ? conjugation, the nonradiative and radiative decay efficiencies, the geometric relaxations, d orbital splitting, and spin–orbit couplings at the optimized S0 and T1 geometries were computed. The results show that complexes with triarylboron substituents may have higher phosphorescence efficiencies than those with cyano groups. Furthermore, complexes with larger ? conjugation (anthracene groups) may weaken the effects caused by the introduction of triarylboron substituents and are less likely to possess enhanced phosphorescence efficiency. Predictions of the absorption spectra and emission colors indicated that complexes with triarylboron substituents would emit blue colors, whereas the emission colors of the complexes with larger ? conjugation would be located in the near-infrared region. This work highlights that the introduction of the triarylboron substituents and appropriate ? conjugation (naphthalene groups) can result in highly efficient phosphorescence in complexes containing donor N-heterocyclic carbene (NHC) ligands. The introduction of triarylboron substituents and appropriate ?-conjugation to the N-heterocyclic (NHC) ligands of PtII complexes may improve their phosphorescence efficiencies and render them good candidates for highly efficient blue emission.

Posted on 2 March 2015 | 12:10 pm


Synthesis, Magnetic Properties, and X-ray Spectroscopy of Divalent Cobalt(II) and Nickel(II) Cubanes [MII4(HL2)4(OAc)4]

Under anaerobic conditions, the reactions of cobalt(II) and nickel(II) acetate tetrahydrate with 2,6-pyridinedimethanol (H2L2, 3) in anhydrous acetonitrile afforded two tetranuclear metal(II) complexes [MII4(HL2)4(OAc)4] (4; MII = Co2+, Ni2+) with a [M4(?3-O)4]4+ cubane core. X-ray structural analyses revealed that both MII cubanes 4a·2CH3OH and 4b·2CH3OH are isostructural and crystallize in the tetragonal space group I41/acd with eight molecules in the unit cell. In the solid state, the orientation of the cubane cores of 4 and the formation of a 3D framework were controlled by ?–? interactions as well as intra- and intermolecular O–H···O hydrogen bonds. Variable-temperature magnetic susceptibility measurements revealed that the cubanes 4 show a ferrimagnetic coupling scheme that leads to a diamagnetic ground state for both complexes. Core-level X-ray photoelectron spectroscopy confirmed that the Co and Ni ions in 4a and 4b are in a divalent state. X-ray magnetic circular dichroism was performed to extract the spin and orbital contributions to the Co and Ni magnetic moments. We compared the experimental results of the local electronic structures around the Co2+ ions in 4a and the Ni2+ ions in 4b with charge-transfer multiplet simulations. Starting from 2,6-pyridinedimethanol (H2L2, 3) and metal(II) acetate tetrahydrates, divalent CoII and NiII cubanes [MII4(HL2)4(OAc)4] (4) have been synthesized through self-organization. In addition to standard methods (e.g., IR, MS, X-ray analysis), complexes 4 were also characterized by magnetometry and X-ray spectroscopic techniques, including XPS, XAS, and XMCD.

Posted on 2 March 2015 | 12:10 pm


Luminescence Matching with the Sensitivity Curve of the Human Eye: Optical Ceramics Mg8–xMx(BN2)2N4 with M = Al (x = 2) and M = Si (x = 1)

Compounds Mg8–xMx(BN2)2N4 were prepared by solid-state reaction of MgCl2, Li3(BN2), and AlN for M = Al, and of Mg3N2, BN, and Si3N4 for M = Si. Their crystal structures were refined from powder X-ray diffraction data with the space group R$\bar {3}$m for M = Al, Si, and P21/c for M = Si. The structures of Mg8–xMx(BN2)2N4 are characterized by layered arrangements of wurtzite-related block layers alternating with a layer of di-nitridoborate ions along the c-axis direction. Cations in each structure are surrounded tetrahedrally by nitride and di-nitridoborate ions. Europium(II)-doped powders of Mg8–xMx(BN2)2N4 show exceptional broad band emissions in the visible region of the spectrum, on excitation with UV radiation at ?ex = 320 nm. Compounds Mg8–xMx(BN2)2N4 were prepared by solid-state reaction of MgCl2, Li3(BN2), and AlN for M = Al, and of Mg3N2, BN, and Si3N4 for M = Si. Their crystal structures were refined from powder X-ray diffraction data with the space group R$\bar {3}$m for M = Al, Si, and P21/c for M = Si. Eu(II)-doped Mg8–xMx(BN2)2N4 show broad band emissions in the visible region of the spectrum (?ex = 320 nm).

Posted on 27 February 2015 | 11:50 am


Mononuclear Iron(II) Dicarbonyls Derived from NNS Ligands – Structural Models Related to a “Pre-Acyl” Active Site of Mono-Iron (Hmd) Hydrogenase

We report the syntheses and characterization of dicarbonyliron complexes derived from tridentate, ortho-substituted Schiff base pyridine/thioether ligands (RNNS). Metalation reactions of RNNS (R = CH3, OCH3) at low temperature (–78 °C) with [Fe(CO)4(Br)2] afforded the desired complexes [(RNNS)Fe(CO)2Br]Br (2-COBr, 3-COBr). Reactions under similar conditions with more sterically demanding ligands [R = quinoline (Q), ClPh] afforded complex salts of the form [(RNNS)Fe(CO)2Br][Fe(CO)3(Br)3] (4-COFe and 5-COFe, respectively). Alternatively, the metalation of the RNNS ligands (for all R ? H) with [Fe(CO)4(Br)2] in Et2O at room temperature reliably affords the complex species of type [(RNNS)Fe(CO)2Br][Fe(CO)3(Br)3] (2-COFe, 3-COFe, 5-COFe). The metalation reactions of RNNS at only moderately low temperatures (–20 to 0 °C) result in the loss of CO to form the corresponding trigonal-bipyramidal iron(II) dibromide species of type [(RNNS)FeBr2] (2-Br, 4-Br, 5-Br; ?eff ? 5.3 ?B, S = 2). The IR spectrum of each dicarbonyl cation exhibits two ?(CO) stretches at $\tilde {\nu}$ ? 2070 and 2030 cm–1. Low-temperature 1H NMR spectroscopy measurements of 2-CO to 5-CO in CD3CN (–35 to 5 °C) revealed sharp resonances in the diamagnetic region. Under dark conditions, each dicarbonyl species is relatively stable (<10?% loss of CO, 1–2 h). However, photolysis revealed varying extents of photostability (stability rank: R = OMe?>?Me???Q?>?ClPh). An examination of the structural parameters reveals that higher photostabilities correlate with shorter Fe–C(O) bond lengths, which are induced by variation of the ortho substituent of the pyridine ring. DFT calculations along the putative photolysis pathway revealed that the bulky ligand substituent (in 5-CO) destabilizes the monocarbonyl intermediate, and this is a likely explanation for its more rapid rate of CO photodissociation. Relevance to a possible “apo-active site” of mono-iron hydrogenase (pre-acyl formation) is discussed. A series of iron(II) dicarbonyls are prepared from neutral Schiff base (NNS) ligands. These “phosphine-free” complexes are extremely temperature- and light-sensitive and somewhat like the active site of mono-[Fe] hydrogenase. The Fe(CO)2-bound methylpyridine unit in [(MeNNS)Fe(CO)2Br]+ may represent a “snapshot” of an intermediate during the biogenesis of the Fe–C(=O)acyl-containing active site.

Posted on 27 February 2015 | 11:50 am


CdS/g-C3N4 Hybrids with Improved Photostability and Visible Light Photocatalytic Activity

Novel composite photocatalysts consisting of CdS and graphitic carbon nitride (CdS/g-C3N4) with different ratios of CdS were prepared. The CdS/g-C3N4 composite photocatalysts were characterized in detail and their photocatalytic activity was evaluated by using rhodamine B and colorless metronidazole as probes. Compared with pure g-C3N4, the CdS/g-C3N4 composite exhibits significantly enhanced photocatalytic activity under visible-light irradiation. More importantly, g-C3N4 substantially reinforces the photostability of CdS nanowires even in a nonsacrificial system. The synergistic effect between CdS and g-C3N4 is found to be primarily responsible for enhancement of the separation of photogenerated electrons and holes, which helps improve the photocatalytic performance. A probable photodegradation process of metronidazole was proposed based on an analysis of the degradation products. This study provides new insight into the preparation of highly efficient and stable sulfide-based composite photocatalysts and facilitates their application in a number of environmentally sensitive areas. Nanocomposite photocatalysts CdS/g-C3N4 with different ratios of CdS and graphitic carbon nitride are described as high-performance photocatalysts for environmental remediation. The very stable and recyclable photocatalysts exhibit greatly enhanced photocatalytic activity under visible-light irradiation. Synergistic effects between CdS and g-C3N4 led to efficient separation of charge carriers.

Posted on 27 February 2015 | 11:50 am


Reactions of [Cp2Ti(?2-Me3SiC2SiMe3)] with 1,4-Bis(diphenylphosphanyl)but-2-yne: Coupling and Isomerization versus Phosphorylation

The reactions of [Cp2Ti(?2-Me3SiC2SiMe3)] (1; Cp = ?5-cyclopentadienyl) with 1,4-bis(diphenylphosphanyl)but-2-yne (2) have been investigated and found to yield a mixture of products. From these, through the coupling of 2, the tetrasubstituted titanacyclopentadiene [Cp2Ti(CCH2PPh2)4] (3) was isolated. In addition, small amounts of very unusual complexes were obtained and characterized. In one case, the substrate 2 isomerized to the allene Ph2PC(H)=C=C(H)CH2PPh2, which formed the complex [Cp2Ti{?3-Ph2PC(H)=C=C(H)CH2PPh2}] (4) through the coordination of a double bond and one of the phosphorus atoms. Another complex, [Cp2Ti{-C(CH2PPh2)=C(CH2PPh2)P(Ph2)H-}] (5), was identified to be the result of a formal hydrophosphorylation of the substrate 2 by HPPh2, and features a Ti–H–P bridge. It is not clear how HPPh2 was formed. One possible explanation is the dehydrophosphorylation of the substrate with the formation of HPPh2 and the butatriene H2C=C=C=C(H)PPh2 [tautomer of the but-2-en-3-yne HC?C-CH=C(H)PPh2]. The molecular structures of complexes 4 and 5 were determined by X-ray analysis. Cuttings and Couplings: The reactions of 1,4-bis(diphenylphosphanyl)but-2-yne with [Cp2Ti(?2-Me3SiC2SiMe3)] have been investigated. An initial alkyne coupling reaction led to a metallacyclopentadiene. Thermal treatment then led to an allene complex by a 1,3-H shift in the coordinated alkyne. In addition, a highly unusual complex with a Ti–H–P bridge was obtained by phosphorylation of the alkyne.

Posted on 27 February 2015 | 11:50 am


Imidazolium 1,3-Benzazaphospholide Ion Pairs with Strong C–H···N Hydrogen Bonds – Synthesis, Structures, and Reactivity

The treatment of 2-phenyl-1H-1,3-benzazaphosphole (H[2-ph-bp], 1) with free 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes, 2) and 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIMes, 3) afforded two imidazolium 1,3-benzazaphospholides, [1,3-bis(2,4,6-trimethylphenyl)imidazolium 2-phenyl-1,3-benzazaphospholide [(IMesH)+(2-ph-bp)–, 4] and 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolium 2-phenyl-1,3-benzazaphospholide [(SIMesH)+(2-ph-bp)–, 5], which further reacted with carbodiimide to give 2-(N,N?-diisopropylcarbamimidoyl)-1,3-bis(2,4,6-trimethylphenyl)imidazolium 2-phenyl-1,3-benzazaphospholide (6) and 2-(N,N?-diisopropylcarbamimidoyl)-1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolium 2-phenyl-1,3-benzazaphospholide (7), respectively. These compounds were characterized by multinuclear (1H, 13C{1H}, and 31P{1H}) NMR and IR spectroscopy, and X-ray diffraction analysis. The structures feature ion pair conformation in the solid state with strong charge-assisted C–H···N or N–H···N interaction. The treatment of 1H-1,3-benzazaphosphole with N-heterocyclic carbenes produces ionic species exhibiting strong charge-assisted hydrogen bonds, which further react with carbodiimide to give carbamimidoylimidazolium 1,3-benzazaphospholides. The crystal structures of the complexes indicate ion pair conformation in the solid state.

Posted on 27 February 2015 | 11:50 am


A Model Study on Molecular Properties and Mechanistic Investigations of P=C=E14 Molecules

The bonding properties and the potential energy surfaces for the chemical reactions of heteroallenic compounds with a –P=C=E14< pattern are studied by using density functional theory (M06-2X/Def2-SVPD). Five Mes*P=C=E14(tBu)Tip species, for which E14 = C, Si, Ge, Sn, and Pb, were used as model reactants in this work. The theoretical evidence shows that Mes*P=C=E14(tBu)Tip molecules have both P=C and C=E14 double bonds. Four types of chemical reaction – water addition, acetylene [3+2] cycloaddition, ketone [2+2] cycloaddition, and selenium [1+2] cycloaddition – have been used to study the reactive activity of these group 14 heteroallenic molecules. This theoretical work predicts that the heavier the group 14 element (E14) in the heteroallenic –P=C=E14< compounds, the smaller is its singlet–triplet energy splitting, the lower is its activation barrier, and the more rapid are its chemical reactions with various chemical species. As a result, this theoretical investigation shows that the relative reactivity of –P=C=E14< increases in the order: –P=C=C<, –P=C=Si<, –P=C=Ge<, –P=C=Sn<, and –P=C=Pb<. M06-2X computational results reveal that Mes*P=C=E14(tBu)Tip compounds contain both P=C and C=E14 double bonds in nature. Moreover, this theoretical work suggests that the smaller the atomic number of the group 14 element, E14, in the heteroallenic –P=C=E14< molecule, the more kinetically and thermodynamically stable is its heteroallenic –P=C=E14< species towards various chemical reactions.

Posted on 27 February 2015 | 11:40 am


Amine-bis(phenolato)cobalt(II) Catalysts for the Formation of Organic Carbonates from Carbon Dioxide and Epoxides

New monometallic amine-bis(phenolato)cobalt(II) [(ONNO)RCoII] (R = CMe2Ph; Cl; Br) complexes have been synthesized and fully characterized including X-ray crystallographic analysis. These CoII complexes show good activity for the formation of cyclic propylene carbonate in combination with tetrabutylammonium bromide (TBAB) as a co-catalyst. The reaction parameters such as carbon dioxide pressure, co-catalyst loadings and temperature were varied to determine the ideal reaction conditions. These catalysts were also employed in copolymerization reactions of cyclohexene oxide/CO2 and propylene oxide/CO2. [(ONNO)ClCoII]*(MeOH) was found to effectively copolymerize cyclohexene oxide (CHO) and CO2. This is the first reported amine-bis(phenolato) cobalt(II) complex to be active in the copolymerization of CO2 and CHO. In-depth stability studies were conducted (Evan's method) to validate CoII as the active species required for copolymerization. End-group analysis via NMR, ESI-MS and MALDI-TOF revealed the presence of 4-(dimethylamino)pyridine (DMAP) and methoxy terminated chains. New amine-bis(phenolato)cobalt(II) complexes were synthesized and employed in the coupling and copolymerization of carbon dioxide and epoxides. In combination with DMAP, complex 3 enabled poly(cyclohexene) carbonate generation. End-group analysis found DMAP and methoxy terminated polymer chains due to chain-transfer and the active species for CHO/CO2 copolymerization was found to be CoII.

Posted on 27 February 2015 | 11:30 am


[Ag{S2CNR(C2H4OH)}] as Single-Source Precursor for Ag2S – Synthesis, Decomposition Mechanism, and Deposition Studies

Silver(I) dithiocarbamates [Ag{S2CNR(C2H4OH)}] (3a, R = Me; 3b, R = Bu) were accessible by the reaction of AgNO3 with K{S2CNR(C2H4OH)} (2a, R = Me; 2b, R = Bu). Alternatively, 3b could be prepared by the condensation of CS2 and Ag2O with NHBu(C2H4OH) (1b). The thermal behavior of 3 was studied by thermogravimetric (TG) analysis. A two-step decomposition process leads to the formation of ?-Ag2S, as evidenced by X-ray powder diffraction studies. A decomposition mechanism of 3a to form Ag2S through the release of 3-methyloxazolidine-2-thione is discussed based on TG–MS, GC–MS, and NMR experiments. Because of the better solubility of 3b, this complex was tested for Ag2S spin-coating deposition studies on different substrates (SiO2/Si, TiN/SiO2/Si, glass) with subsequent annealing at 450 °C under a N2 atmosphere. Film thickness, composition, and morphology of the as-deposited films were determined by XRD, SEM, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, which showed the formation of 200 nm thick, conformal, adherent, monoclinic ?-Ag2S layers. The synthesis, thermal behavior, and decomposition mechanism of [Ag{S2CNR(C2H4OH)}] (R = Me, Bu) is discussed. Its application as a single-source spin-coating precursor for thin-film ?-Ag2S fabrication is reported.

Posted on 27 February 2015 | 11:30 am


On the Thermal Stability and Structures of Layered Double Hydroxides Mg1–xAlx(OH)2(NO3)x·mH2O (0.18???x???0.38)

Nitrate-based layered double hydroxides, Mg1–xAlx(OH)2(NO3)x·mH2O, have been investigated to settle issues relating to stability towards humidity, dehydration and staging, nitrate group orientation, Al migration and crystal structure. Raman and IR spectroscopy together with modelling methods proved that flat-lying water and nitrate become tilted towards [001] at higher nitrate concentrations, accompanied by expansion along the c-axis. The distribution of the molecular tilts is greatest for x = 0.25, which explains the extraordinary broad diffraction peaks. The unit cell volume was modified for all samples when subjected to moist air, most strongly for x = 0.25. On heating, in situ synchrotron diffraction data showed continuous changes along the c-axis during dehydration of samples with x = 0.20 and 0.33. For x = 0.25, an intermediate phase appeared. Dehydroxylation was initiated at the OH groups bonded to the cations MgAl2, Mg2Al and Mg3 (in said order), whereas complete nitrate loss occurred at higher temperatures for higher Al contents. Some aluminium simultaneously moved to tetrahedral sites, which, according to 1H–27Al CP NMR spectroscopy, lack protons in their near neighbourhood. In contrast, octahedral aluminium remains surrounded by protons during decomposition. For the metastable oxide product, neutron diffraction indicated that 2/3 of aluminium reside in tetrahedral interstices. This oxide is defective, probably mimicking wüstite rather than a regular rock salt structure. Structural aspects of nitrate-based layered double hydroxides Mg1–xAlx(OH)2(NO3)x·mH2O have been investigated by various experimental and theoretical methods. The main focus was on the orientation of the NO3– groups in the interlayer gallery, the reversible hydration/dehydration process and the transport of Al from octahedral to tetrahedral sites during the formation of a metastable rock salt oxide.

Posted on 27 February 2015 | 11:30 am


Synthesis and Catalytic Activity of Molybdenum–Nitride Complexes Bearing Pincer Ligands

Molybdenum–nitride complexes bearing pincer ligands have been designed, prepared, and characterized spectroscopically. The synthetic method described in this paper provides a convenient and useful approach to the preparation of cationic molybdenum(V)–nitride complexes that may act as catalysts for the formation of ammonia from molecular dinitrogen under ambient reaction conditions.. Molybdenum–nitride complexes bearing pincer ligands have been designed, prepared, and characterized spectroscopically. The catalytic activities of these molybdenum–nitride complexes have been investigated in the formation of ammonia from molecular dinitrogen under ambient conditions.

Posted on 27 February 2015 | 11:30 am


Lanthanoid Induced C–F Activation of All Fluorine Atoms of One CF3 Group

The lanthanum formamidinate complex [La(CF3Form)3] {CF3FormH = N,N?-bis(2-trifluoromethylphenyl)formamidine}, which has six La–F interactions in the solid-state structure, readily undergoes C–F activation of all fluorine atoms of one CF3 group to give LaF3, and two isomeric polytrifluoromethylphenyl-substituted polyamidines, one containing a 1,2,3,4-tetrahydroquinazoline heterocyclic core. The lanthanum formamidinate complex [La(CF3Form)3] {CF3FormH = N,N?-bis(2-trifluoromethylphenyl)formamidine} readily undergoes C–F activation of all fluorine atoms of one CF3 group to give LaF3, and two isomeric polytrifluoromethylphenyl-substituted polyamidines, one containing a 1,2,3,4-tetrahydroquinazoline heterocyclic core.

Posted on 25 February 2015 | 9:50 am


Syntheses, Structures, and Photophysical Properties of Eu and Lu Diketonates with a Neutral Polydentate Imidazolylmethanamine Ligand

The Schiff base NNO ligand 1-(furan-2-yl)-N-[(2-methyl-1H-imidazol-4-yl)methylene]methanamine was synthesized and structurally characterized by XRD crystallography, mass spectrometry, and NMR spectroscopy. Quantum-chemical calculations revealed conformational flexibility of the ligand backbone to give two different conformations with nearly equal ground-state energies. The orientation of two nitrogen atoms and the oxygen atom in one conformation is a good fit for the NNO tridentate coordination mode, whereas the other would allow the NN coordination mode only. Two lanthanide complexes [Ln(tta)3(NNO)] (Ln = EuIII and LuIII; tta = thenoyltrifluoroacetone) were prepared and studied spectroscopically. The structures of the complexes were optimized by the DFT approach. The NNO ligand in the Eu complex displays tridentate NNO coordination, whereas the ligand is only NN-coordinated in the Lu complex. The Eu complex shows bright red metal-centered phosphorescence under excitation into the ligand (?–?*) absorption bands with a quantum yield of ca. 80?% and a lifetime of 580 ?s. A mechanism for energy transfer between the ligands and metal centers was suggested and confirmed by DFT and time-dependent DFT (TDDFT) studies. An organic light-emitting diode (OLED) device based on the Eu complex incorporated into a poly(9-vinylcarbazole) (PVK) matrix was prepared. A study of the characteristics of the device revealed electrochromism of the system owing to variations in the efficacy of metal-centered and matrix emission at different strengths of applied electric field. Neutral EuIII and LuIII diketonate complexes with a Schiff base NNO ligand are studied spectroscopically. The Eu complex shows red metal-centered phosphorescence with a quantum yield of ca. 80?%. An organic light-emitting device (OLED) with the Eu complex in a poly(9-vinylcarbazole) (PVK) matrix reveals electrochromism owing to variations in the efficacy of the metal-centered and matrix emission.

Posted on 25 February 2015 | 9:50 am


A Cationic Polyelectrolyte-Controlled Liquid Mineral Precursor Process in the BaCO3 System

Biomimetic BaCO3 materials with various morphologies have been synthesized in a cationic polyelectrolyte-controlled mineral solution. Investigations showed that the mineral solution initially underwent a phase separation to produce a condensed liquidlike amorphous intermediate. This mineral solution was a typical reaction-diffusion field, in which concentric ring patterns were frequently observed. Subsequently, overgrowth fibers were seen growing on large microspheres and their growth could be interpreted in terms of a mesocrystal self-assembly process. This work opens up the possibility of using positively charged polyelectrolytes to design a very wide range of inorganic materials. A polymer-induced liquid mineral precursor (PILP) provides a general pathway towards biomimetic materials with complex morphology. In this article, we expand the conception of cationic polyelectrolyte-induced liquid precursors to other inorganic systems, such as barium carbonate. Mesocrystal fibers and a self-organized concentric ring pattern were synthesized in the mineral solution.

Posted on 23 February 2015 | 11:20 am


One-Step Green Synthesis of Multifunctional Fe3O4/Cu Nanocomposites toward Efficient Reduction of Organic Dyes

Noble-metal-derived functional materials have played indispensable roles in the reduction of dye under aqueous conditions; however, their cost and separation are great limitations on their wider practical applications. Therefore, an alternative preparation of comparable materials with low cost and good ease of separation is required. Herein magnetic microspheres (i.e., Fe3O4/Cu) were synthesized through a green single-step solvothermal method for the first time with ethylene glycol serving as reductant and reaction media. The prepared materials were characterized by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectrometry, a vibrating sample magnetometer, and so forth. Additionally, by employing the reduction of 4-nitrophenol to 4-aminophenol as a model reaction, the effects of preparation time and the initial dosage of Cu(NO3)2 on the rate constant of the catalytic reduction reaction were systematically investigated. Moreover, the obtained hybrid nanocatalysts were also applied to reduce and degrade common organic dyes (rhodamine B and methylene blue) in the presence of NaBH4. Quite significantly, it was shown that it could catalytically degrade different organic dyes with excellent catalytic performance and high stability in recycled reactions up to five times. More interestingly, the material can be easily separated from the catalytic system for further use. An Fe3O4/Cu nanocatalyst that exhibits excellent catalytic performance in the degradation of 4-nitrophenol (4-NP) (the reaction was accomplished within 4 min), rhodamine B (within 3 min), and methylene blue (within 1 min) as well as superior stability (can be reused at least five times) was successfully synthesized through a green one-step solvothermal method with ethylene glycol as reductant and reaction media.

Posted on 20 February 2015 | 11:10 am


Differential Reactivity of [TpRu(?2P,N-iPr2PXPy)Cl] (X = NH, S) Bearing Hemilabile Coligands Towards NaBArF4, Lithium Acetylide, and Acetylenes

In contrast with [TpRu(?2P,N-iPr2PNHPy)Cl] (1a, Tp = trispyrazolylborate), [TpRu(?2P,N-iPr2PSPy)Cl] (1b) reacts with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4) in fluorobenzene under nitrogen to afford the dinuclear complex [{TpRu(?2P,N-iPr2PSPy)}2(?-Cl)][BArF4] (1b?). Through diverse synthetic strategies, a series of neutral acetylides [TpRu(C?CR)(?2P,N-iPr2PXHPy)] [X = NH; R = Ph (2a), SiMe3 (2b); X = S; R = Ph (2c), p-C6H4Br (2d), COOMe (2e)], cationic vinylidene complexes [TpRu(=C=CHR)(?2P,N-iPr2PNHPy)]+ [X = NH; R = Ph (3a), SiMe3 (3b); X = S; R = Ph (3c), p-C6H4Br (3d)] and [TpRu(=C=CH2)(?2P,N-iPr2PNHPy)]+ (3e), and a cationic ?2-alkyne complex [TpRu(?2-HC?CCOOMe)(?2P,N-iPr2PSPy)][BArF4] have been efficiently synthesized from 1a and 1b. The methoxy(methyl)carbene complexes [TpRu{=C(OMe)CH3}(?2P,N-iPr2PXPy)][BPh4] [X = NH (5a), S (5b)] were isolated from the reactions of 1a and 1b with acetylene gas in the presence of NaBArF4 in methanol. The deprotonation of the cationic vinylidenes derived from 1b with KtBuO affords the corresponding neutral acetylide complexes, which undergo facile protonation with CF3SO3H to reproduce the cationic vinylidenes quantitatively. The behaviors of ruthenium complexes bearing 2-pyridyl(diisopropylphosphanyl)amine (iPr2PNHPy) or 2-pyridyl(diisopropylphosphanyl)thioether (iPr2PSPy) ligands are compared. The main emphasis is on the differential reactivity of [TpRuCl(iPr2PXPy)] (X = NH, S; Tp = trispyrazolylborate) towards NaBArF4 {BArF4 = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate}, lithium acetylide, and acetylenes.

Posted on 19 February 2015 | 11:53 am


Bis- and Tris(carboxylato)platinum(IV) Complexes with Mixed Am(m)ine Ligands in the trans Position Exhibiting Exceptionally High Cytotoxicity

A series of seven diam(m)inebis(carboxylato)dihydroxidoplatinum(IV) and eleven diam(m)inetris(carboxylato)hydroxidoplatinum(IV) complexes with am(m)ine ligands in the trans position was synthesized and characterized by multinuclear 1H, 13C, 15N, 195Pt NMR spectroscopy. IC50 values for all eighteen substances were determined by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay for three human cancer cell lines. In cisplatin-sensitive CH1(PA-1) cancer cells, diam(m)inebis(carboxylato)dihydroxidoplatinum(IV) complexes displayed 50?% inhibitory concentrations in the micromolar range, whereas for the most lipophilic compounds of the diam(m)inetris(carboxylato)hydroxidoplatinum(IV) series, promising IC50 values in the nanomolar range were found. A total of 18 bis- and tris(carboxylato)platinum(IV) complexes with am(m)ine ligands in the trans position were synthesized and characterized. Their cytotoxicity was investigated for three human cancer cell lines; the most lipophilic compounds showed promising IC50 values down to the nanomolar range.

Posted on 19 February 2015 | 11:53 am


Three Alkali Metal Lead Orthophosphates – Syntheses, Crystal Structures and Properties of APbPO4 (A = K, Rb, Cs)

Three alkali metal lead orthophosphates, APbPO4 (A = K, Rb, Cs), have been synthesized by conventional solid-state reaction. The single-crystal X-ray structural analyses revealed that they crystallize in the same space group, Pnma (No. 62), but they are not all isostructural. APbPO4 (A = K, Rb) are isostructural, and the three-dimensional (3D) structure of RbPbPO4 (representative) consists of [Pb1|Rb1O4]? chains connected with isolated PO4 tetrahedra, the Pb2|Rb2 atoms filling the pore space. The 3D structure of CsPbPO4 consists of another kind of chains, [PbO4]?, connected with isolated PO4 tetrahedra, and the Cs atoms reside in the channel. Thermal, IR spectroscopy, and UV/Vis/NIR diffuse reflectance spectroscopy analyses have also been performed. In addition, first-principle theoretical studies were carried out to aid in the understanding of the electronic structures and the projected density of states of CsPbPO4. Three alkali metal lead orthophosphates, APbPO4 (A = K, Rb, Cs), have been synthesized by conventional solid-state reaction. They crystallize in the same space group, Pnma, but they are not all isostructural.

Posted on 18 February 2015 | 11:50 am


Triphenylguanidine-Promoted ortho-Metalation Reaction in a Triply Bonded Dirhenium System – Spectroscopic, Structural, and Computational Studies

Triphenylguanidine-promoted ortho-metalation reactions have been observed in reactions between the triply bonded dirhenium(II) complex Re2Cl4(?-Ph2PCH2PPh2)2 (1) and different para-substituted triphenylguanidine ligands (HTPGR) in ethanol under reflux. The products are of the type Re2Cl2(?-dppm)(?-dppm°)(TPGR) [2(R), dppm = Ph2PCH2PPh2, ?-dppm° represents the ortho-metalated dppm ligand and R = H, 2(H); Me, 2(Me), and OMe, 2(OMe)]. These are the first examples of ortho-metalated dirhenium complexes with bridging dppm ligands. These complexes have very similar spectral (UV/Vis, IR, and NMR) and electrochemical properties, which are also reported. The solid-state structure of 2(H) has been established by single-crystal X-ray diffraction [Re–Re distance 2.2741(6) Å]. In the solid state, the molecules are linked by ?···? and C–H···? intermolecular interactions and form infinite supramolecular chains. Anion···? interactions have also been revealed in the solid state. The electronic structures of the complexes are also scrutinized by density functional theory (DFT) calculations. A series of ortho-metalated dirhenium complexes are prepared by reacting Re2Cl4(?-Ph2PCH2PPh2)2 with different para-substituted triphenylguanidine ligands (HTPGR, R = H, Me, OMe) and characterized by different spectroscopic techniques and by X-ray crystallography. The complexes have similar spectral and electrochemical properties, which are consistent with the results of a theoretical study.

Posted on 18 February 2015 | 11:50 am


Customized Buchwald-Type Phosphines Bearing an “Inverted” Pyrimidinium Betaine as an Aryl Group Surrogate – Synthesis and Coordination Chemistry with Gold(I)

A new ligand scaffold inspired by Buchwald-type phosphines is disclosed. Its design consists of the formal replacement of the distal aryl group of the original archetype by a pyrimidinium betaine connected to the o-phosphinophenyl moiety through the C-5 position of its malonate subunit. A productive synthetic pathway towards this phosphine is described along with its ability to coordinate to a gold(I) center. A weak bonding interaction between the metal center and the malonate group is observed in the solid state. The attachment of a pyrimidinium betaine at the ortho position of one of the aryl groups of a triarylphosphine is proposed as a means to diversify the already well-documented palette of Buchwald-type phosphines. The structure of a gold complex reveals that the malonic carbon center that acts as the linker also weakly interacts with the gold center.

Posted on 18 February 2015 | 11:50 am


Dinuclear DOTA-Based GdIII Chelates – Revisiting a Straightforward Strategy for Relaxivity Improvement

The need for magnetic resonance imaging (MRI) contrast agents with improved relaxivity maintains the development of new GdIII chelates as an intensive and demanding field of research. In this work, we introduce the new dimeric chelators bis{1,4,7,10-tetraazacyclododecane-1-[(6-amino)hexanoic]-4,7,10-triacetic acid}adipate [L2, bis(DOTA-AHA)adipate] and bis{1,4,7,10-tetraazacyclododecane-1-[(6-amino)hexanoic]-4,7,10-triacetic acid}1,3-phenyldiacetate [L3, bis(DOTA-AHA)1,3-phenyldiacetate], which are based on the bifunctional ligand 1,4,7,10-tetraazacyclododecane-1-[(6-amino)hexanoic]-4,7,10-triacetic acid (L1, DOTA-AHA). Their GdIII chelates were studied by variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17O NMR spectroscopy to measure their relaxivities and the parameters that govern them. The rates of exchange of inner-sphere water from the monomer GdL1 and from the two dinuclear chelates Gd2L2 and Gd2L3 are very similar (298kex ? 6.5?×?106 s–1) and slightly faster than that for [Gd(DOTA)H2O]– (298kex = 4.1?×?106 s–1). All three compounds form weakly bound aggregates with equilibrium constants 298K of 2.9, 15.6, and 14.6 for GdL1, Gd2L2, and Gd2L3, respectively. Even though the aggregates contain only 10 to 15?% of the total amount of GdIII ions, a marked increase in relaxivity between 30 and 100 MHz is observed. Furthermore, the distance between the two GdIII centers in the dinuclear compounds has been determined by double electron–electron resonance (DEER) spectroscopy experiments and by molecular modeling studies, which afforded comparable distances. The linkers between the chelating moieties allow GdIII–GdIII distances of ca. 3.0 nm for the completely stretched linker conformation and less than 1.9 nm for the conformation with the metal centers at a closer distance. These metal-to-metal distances by themselves cannot explain the considerably long tumbling times of the chelates in solution. Only a model consistent with some level of aggregation for the dinuclear chelates in aqueous solution could satisfactorily explain our results. Two DOTA-based dimeric chelators are developed, and their dinuclear GdIII chelates are studied by variable-temperature 1H nuclear magnetic relaxation dispersion (NMRD) and 17O NMR spectroscopy. The distance between the GdIII centers is determined by double electron–electron resonance and by molecular modeling. Only a model with some level of aggregation could satisfactorily explain our results.

Posted on 18 February 2015 | 11:50 am


Further Insight into Uranium and Thorium Metaphosphate Chemistry and the Effect of Nd3+ Incorporation into Uranium(IV) Metaphosphate

A tetragonal modification of uranium polymetaphosphate U(PO3)4, a mixed U4+/Nd3+ polymetaphosphate “(U0.62Nd0.38)(PO3)4”, and two new tetraphosphates, Th(P4O12) and U(P4O12), were synthesized. The structures of the obtained materials were characterized by X-ray diffraction and Raman spectroscopy. The presence of Nd in (U0.62Nd0.38)(PO3)4 was proven by energy-dispersive X-ray spectroscopy (EDX), and the measured degree of substitution for U agrees well with the X-ray crystallography results; however, the mechanism of the necessary charge compensation could not be identified. The cation arrangements in the crystal structures of thorium and uranium polymetaphosphates have been studied in terms of Voronoi–Dirichlet polyhedra. Different conformations of the tetraphosphate polyanions were observed in the crystal structures of Th(P4O12) and U(P4O12). The Raman spectrum of a single crystal of Th(P4O12) was recorded, and the bands were assigned. Two new polymorphic modifications of uranium metaphosphate are obtained, and their crystal structures are elucidated as well as those of previously reported thorium and uranium tetraphosphates. The uranium atoms are partially substituted by neodymium atoms in the structure of one of the uranium metaphosphates, and the substitution significantly affects the structure.

Posted on 18 February 2015 | 11:50 am


Controlled Synthesis of Phase-Pure Zeolitic Imidazolate Framework Co-ZIF-9

The synthesis of phase-pure Co-ZIF-9, an important cobalt-based zeolitic imidazolate framework, could be achieved by modification of the reported synthesis procedure through pH adjustment of the starting synthesis mixture. The phase-pure Co-ZIF-9 material obtained has been characterized by a combination of UV/Vis, FTIR, and Raman spectroscopy as well as by thermogravimetric analysis (TGA) and XRD and possesses a lower overall crystallinity. This can be explained by the addition of the base for the pH adjustment method. On the basis of these findings, a synthesis pathway for the formation of the secondary phase, cobalt formate, is proposed along with its relationship to the flexibility of the coordination environment of cobalt ions. The crystal structures of both phases have been determined by single-crystal X-ray crystallography, and the resolved structures also reflect the coordination flexibility of the framework cobalt ions. Phase-pure zeolitic imidazolate framework Co-ZIF-9 can be prepared by modification of the commonly used synthesis procedure through pH adjustment, which suppresses the formation of the secondary framework, cobalt formate.

Posted on 18 February 2015 | 11:50 am


Osmium–Nitrosyl Oxalato-Bridged Lanthanide-Centered Pentanuclear Complexes – Synthesis, Crystal Structures and Magnetic Properties

A series of pentanuclear heterometallic coordination compounds of the general formula (Bu4N)5[Ln{Os(NO)(?-ox)Cl3}4(H2O)n] [Ln = Y (for 2) and Dy (for 3?) when n = 0; Ln = Dy (for 3), Tb (for 4), and Gd (for 5) when n = 1] were synthesized by the reaction of the precursor (Bu4N)2[Os(NO)(ox)Cl3] (1) with the respective lanthanide(III) (Gd, Tb, Dy) or yttrium(III) chloride. For the five new complexes, the coordination numbers eight or nine are found for the central metal ion. The compounds were fully characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, magnetic susceptibility measurements, and ESI mass spectrometry. In addition, compound 1 was studied by UV/Vis spectroscopy and cyclic voltammetry. The X-ray diffraction analyses revealed that the anionic complexes consist of a lanthanide or yttrium core bridged through oxalato ligands to four octahedral osmium–nitrosyl moieties. This picture, in which the central ion is eight-coordinate, holds for lanthanide ions with an ionic radius smaller than that of the dysprosium(III) ion. For larger ionic radii, the central metal ion is nine-coordinate, as the coordination sphere is completed by one molecule of water. Only in the case of dysprosium(III), it was possible to obtain complexes with both coordination numbers 8 and 9. This implies that dysprosium(III) is the tilt limit between the two coordination numbers in this series. The bond length Ln–O decreases from Dy to Gd. The nine-coordinate complexes are energetically more favored for lanthanide ions with a radius larger than that of the dysprosium(III) ion, and the eight-coordinate complexes are favored for smaller ions. Magnetic studies of the series of compounds showed that the osmium precursor 1 as well as the yttrium compound 2 are diamagnetic, whereas the magnetism of the gadolinium, terbium, and dysprosium complexes is due to isolated lanthanide ions. Coordination tilt: Depending on the size of the Ln(III) ion, osmium–nitrosyl oxalato-bridged lanthanide-centered pentanuclear complexes exhibit two different coordination numbers, 8 or 9, for the central lanthanide ion, and both numbers are observed for dysprosium.

Posted on 16 February 2015 | 7:10 pm


Electronic Structures of “Low-Valent” Neutral Complexes [NiL2]0 (S = 0; L = bpy, phen, tpy) – An Experimental and DFT Computational Study

The electronic structures of the neutral complexes [Ni(bpy)2]0, [Ni(tpy)2]0, and [Ni(phen)2]0 (bpy = 2,2?-bipyridine; tpy = 2,2?:6?,2?-terpyridine; phen = 1,10-phenanthroline) have been investigated by a combination of UV/Vis spectroscopy, magnetochemistry, and X-ray crystallography {the structures of [Ni(bpy)2]0, [Ni(tpy)Cl]0, [Cu(bpy)2](PF6)2 (reinvestigation), and [(bpy)2Cu(?2-NO3)Cu(bpy)2](PF6)3 are reported herein}. To further clarify the electronic structures of the title compounds and elucidate those of the electron transfer series produced by their reduction and oxidation, broken-symmetry (BS) density functional theory (DFT) calculations were performed for [Ni(bpy)2]m (m = 2+, 1+, 0, 1–, 2–), [Ni(bpy)3]m (m = 3+, 2+, 1+, 0, 1–, 2–), [Ni(tpy)2]m (m = 3+, 2+, 1+, 0), and, for calibration purposes, [Zn(phen)(NH3)xCl(2–x)]0 (x = 2, 1, 0). Through the aforementioned studies, it was shown that none of the so called “low-valent” Ni complexes contain zero-valent Ni. Instead, they each contain at least one (bpy·)1–, (tpy·)1–, or (phen·)1– ?-radical monoanionic ligand. More specifically, they are all four-coordinate and possess the following electronic structures: [NiI(bpy·)(bpy0)] (delocalized), [NiI(tpy·)(tpy0)] (delocalized), and [NiII(Mephen·)2] (Mephen = 2,9-dimethyl-1,10-phenanthroline). In addition, all members of the series [Ni(bpy)2]m with m?? 1+ contain a NiI ion (d9, SNi = 1/2), and the redox processes that link them are ligand-centered. A similar finding was made for six-coordinate [Ni(bpy)3]m and [Ni(tpy)2]m, but in this case complexes with m?? 2+ contain Ni ions posessing an invariant +II oxidation state (d8, SNi = 1). The electronic structures of the two series of complexes [Ni(bpy)3]n (bpy = 2,2?-bipyridine; n = 2–, 1–, ..., 3+) and [Ni(bpy)2]m (m = 1–, ..., 3+) have been studied experimentally and computationally (DFT). All octahedral species contain a NiII ion, and the reductions are strictly ligand-centered, whereas the [Ni(bpy)2]m series contains tetrahedral NiII and NiI ions.

Posted on 16 February 2015 | 7:10 pm


Synthesis and Structural Study of Tetravalent (Zr4+, Hf4+, Ce4+, Th4+, U4+) Metal Complexes with Cyclic Hydroxamic Acids

Six- and seven-membered cyclic hydroxamic acids, such as 1-hydroxypiperidine-2-one (1H, 1,2-PIPOH) and 1-hydroxyazepan-2-one (2H), have recently been identified in some mixed siderophores as one of their three chelating subunits. Compared to their ubiquitous noncyclic counterparts, cyclic hydroxamates are preorganized for metal binding. Surprisingly, the coordination chemistry of these bidentate, monoanionic ligands remains virtually unknown, even in the case of iron(III). We report herein the first structural study of the complexes of 1– and of 6–, an unsaturated seven-membered ring analog of 2–, with tetravalent cations of transition metals (zirconium and hafnium), lanthanide (cerium), and actinides (thorium and uranium). Structural characterization by means of X-ray crystallography of the corresponding ML4 complexes evidenced distorted square antiprismatic coordination geometries with the exception of U4+, which favors a dodecahedral arrangement. 1-Hydroxypiperidine-2-one (1H, 1,2-PIPOH) is a cyclic hydroxamic acid that occurs in several siderophores as one of the three FeIII binding units. It can form neutral homoleptic complexes with tetravalent transition-metal (Zr and Hf), lanthanide (Ce), and actinide (Th and U) cations with a diversity of coordination stereochemistries ranging from the square antiprism to the dodecahedron.

Posted on 16 February 2015 | 7:10 pm


Asymmetric Base-Free Michael Addition at Room Temperature with Nickel-Based Bifunctional Amido-Functionalized N-Heterocyclic Carbene Catalysts

A series of nickel-based chiral bifunctional catalysts (1d–3d) with N-heterocyclic carbene (NHC) ligands derived from (1R)-(–)-menthol, (1S)-(–)pinene, and (1R)-(+)-camphor have been successfully designed for asymmetric Michael addition reactions under base-free conditions. The NHC complexes, namely, [1-R-3-{N-(phenylacetamido)}imidazol-2-ylidene]2Ni [R = (1S)-menthyl (1d), (1S)-pinane (2d), and (1R)-isobornyl (3d)], bearing chiral ancillaries on the amido-functionalized side arms of the NHC ligands, performed the bifunctional catalysis of the asymmetric base-free Michael addition reaction of the ?-methyl cyano ester substrates ethyl 2-cyanopropanoate (4), isopropyl 2-cyanopropanoate (5), and tert-butyl 2-cyanopropanoate (6) with the activated olefinic substrates methyl vinyl ketone (7) and acrylonitrile (8) in 63–98?% yields with enantiomeric excess (ee) values of 2–75?% at room temperature in 8 h. More interestingly, only the longest of the three catalysts, the menthol derivative 1d, showed significant chiral induction of up to 75?%?ee; this has been attributed to the reduction of the steric influence owing to the relatively distant dispositions of the chiral ancillaries from the catalytically active metal center that arise as a consequence of the cis geometries of 1d–3d. A series of nickel-based chiral bifunctional catalysts with N-heterocyclic carbene ligands derived from readily available and inexpensive (1R)-(–)-menthol, (1S)-(–)pinene, and (1R)-(+)-camphor synthons successfully catalyze asymmetric base-free Michael addition reactions under ambient conditions.

Posted on 16 February 2015 | 7:10 pm


Coordinative Flexibility of a Thiophenolate Oxazoline Ligand in Nickel(II), Palladium(II), and Platinum(II) Complexes

The synthesis, full characterization, and molecular structures of seven new coordination compounds that feature the 2-(4?,4?-dimethyloxazolin-2?-yl)thiophenolate ligand (S-Phoz) with group 10 metals Ni, Pd, and Pt in the +II oxidation state are presented. The ML2 complexes [Pt(S-Phoz)2] (1a), [Pd(S-Phoz)2] (1b), and [Ni(S-Phoz)2] (2) were prepared starting from MCl2. Compound 1a was obtained isomerically pure in a trans arrangement, whereas its Pd analogue 1b exhibits a dynamic, solvent-dependent cis/trans equilibrium, and 2 adopts a tetrahedral arrangement. The reaction of LiS-Phoz with [cis-MCl2(PPh3)2] precursors resulted in full replacement of the PPh3 for M = Ni and in partial substitution for M = Pt, Pd to yield [Ni(S-Phoz)2] (2), [Pt(?2-S-Phoz)(?1-S-Phoz)(PPh3)] (3a), and [Pd(?2-S-Phoz)(?1-S-Phoz)(PPh3)] (3b). The Pd compound 3b exhibits an interesting solvent-dependent equilibrium with 1b and PPh3 as demonstrated by 1H and 31P NMR spectroscopy. Compounds [{PdCl(S-Phoz)}2] (4) and [PdCl(S-Phoz)(PPh3)] (5) were synthesized from [PdCl2(NCMe)2]. Molecular structures of compounds trans-1a, trans-1b, 2, 3a, 3b, 4, and 5 were determined by single-crystal X-ray diffraction studies. With the exception of the Ni complex 2, all compounds exhibit distorted square-planar geometries. A series of nickel, palladium, and platinum complexes that contain a thiophenolate oxazoline ligand were prepared. The ligand coordinates preferably in a bidentate manner but shows high coordinative flexibility depending on the metal center.

Posted on 16 February 2015 | 4:50 pm


Synthesis of the First Example of Selenium-Containing Platinum(II)–Alkenylarylalkynyl Complexes

A synthetic method has been developed to construct a new series of selenium-containing trans-platinum(II)–bis(alkenylarylalkynyl) complexes with general formula trans-[(PR3)2Pt{C?C–Ar–C(SePh)=CH(SePh)}2] (R = ethyl, phenyl, and Ar = phenylene, biphenylene), having two phenylseleno moieties on each alkenyl backbone. Reaction of the diterminal alkynyl ligand of trans-platinum(II)–bis(alkynylarylalkynyl) complex 1 with an amount slightly in excess of two equivalents of diphenyl diselenide in chloroform readily affords trans-platinum(II) complex 2 upon irradiation, in good to excellent yields with good regioselectivity. As compared to the absorption band of platinum(II) complexes 1, it was found that the position of the lowest energy absorption bands of platinum(II) complexes 2 are redshifted. A convenient way has been developed to construct selenium-containing platinum(II)–bis(alkenylarylalkynyl) complexes having two phenylseleno moieties on each alkenyl backbone (Ar = phenylene and R = ethyl for 1a/2a; Ar = phenylene and R = phenyl for 1b/2b; Ar = biphenylene and R = ethyl for 1c/2c; Ar = biphenylene and R = phenyl for 1d/2d).

Posted on 16 February 2015 | 4:50 pm


Mononuclear Iron(III) Complexes as Functional Models of Catechol Oxidases and Catalases

Mononuclear amino triphenolate iron(III) complexes have been synthesized and characterized (UV/Vis spectroscopy, cyclic voltammetry, ESI-MS, 1H NMR spectroscopy, X-ray diffraction). These complexes act as biomimetic catalysts promoting the aerobic auto-oxidation of 3,5-di-tert-butylcatechol to the corresponding o-benzoquinone at room temperature and displaying catalase activity for the hydrogen peroxide dismutation with remarkable activity (TON up to 4000). Amino triphenolate iron(III) complexes promote effectively, at room temperature, the aerobic auto-oxidation of 3,5-di-tert-buthylcatechol to the corresponding o-benzoquinone (oxidase mimicking) and hydrogen peroxide dismutation (catalase mimicking).

Posted on 16 February 2015 | 4:50 pm


Structural Relationship between the Mg-Containing Nitridosilicates Ca2Mg[Li4Si2N6] and Li2Ca2[Mg2Si2N6]

Ca2Mg[Li4Si2N6] and Li2Ca2[Mg2Si2N6] were synthesized in sealed tantalum ampules with Li as a fluxing agent. Both compounds crystallize in the monoclinic space group C2/m (no. 12). The crystal structures were solved and refined on the basis of single-crystal X-ray diffraction data [Z = 2; Ca2Mg[Li4Si2N6]: a = 5.9059(12), b = 9.817(2), c = 5.6109(11) Å, ? = 94.90(3)°, R1 = 0.015, wR2 = 0.049; Li2Ca2[Mg2Si2N6]: a = 5.5472(11), b = 9.844(2), c = 5.9978(12) Å, ? = 97.13(3)°, R1 = 0.024, wR2 = 0.053]. Ca2Mg[Li4Si2N6] is isomorphic to Ca3[Li4Si2N6] and its crystal structure is homeotypic to that of Li2Ca2[Mg2Si2N6]. Both structures are built up of edge-sharing [Si2N6]10– tetrahedra (bow-tie units). In the nitridolithosilicate Ca2Mg[Li4Si2N6] the bow-tie units are connected via pairs of LiN4 tetrahedra, whereas in the nitridomagnesosilicate Li2Ca2[Mg2Si2N6] the nitridosilicate substructure is connected by chains of MgN4 tetrahedra. Ca2Mg[Li4Si2N6] is only the second example of fourfold planar rectangular coordinated Mg2+ in a nitridosilicate. Li2Ca2[Mg2Si2N6] is the first nitridosilicate with Li+ in threefold coordination. The crystal structures were confirmed by lattice-energy calculations (MAPLE), EDX measurements, and powder X-ray diffraction. Novel Mg-containing nitridosilicates, namely Ca2Mg[Li4Si2N6] and Li2Ca2[Mg2Si2N6], are presented. The nitridolithosilicate Ca2Mg[Li4Si2N6] is the second example of Mg in a fourfold planar rectangular coordination with N in nitridosilicates. Li2Ca2[Mg2Si2N6] is another representative of the novel subgroup of nitridomagnesosilicates with Mg2+ in tetrahedral coordination.

Posted on 16 February 2015 | 4:50 pm


Suzuki Coupling Reactions Catalyzed with Palladacycles and Palladium(II) Complexes of 2-Thiophenemethylamine-Based Schiff Bases: Examples of Divergent Pathways for the Same Ligand

Activation of Suzuki coupling with a complex of palladium varies with the mode of coordination of its ligand. The moisture-/air-insensitive palladacycles and palladium complexes designed using the same ligand (Schiff base, coordinating as an N,C– and N,O– ligand, respectively) have been found to follow different pathways. Palladacycles are more efficient, as their 0.001 mol-% loading gives good conversion (yield > 90?%) in several cases. Higher loading than this is required for Pd complexes to obtain a similar yield. Activation with palladacycles involves the role of nanosized Pd-containing species generated in situ during catalysis, in which, as with PdII complexes, no such particle is formed and Pd0 probably remains protected by the sulfur of the thienyl group. The Schiff bases used here were designed by the reaction of 2-thiophenemethylamine with 2-hydroxybenzophenone/2-hydroxy-4-methoxybenzophenone/2-hydroxyacetophenone (L1/L2/L3). Upon treatment with [PdCl2(CH3CN)2] and [Na2PdCl4] they gave palladacycles [PdL1/L2(CH3CN)Cl] (1/3) and palladium(II) complexes [Pd(L1/L2/L3)2] (2/4/5), respectively. Compounds L1–L3 and their complexes 1–5 were authenticated with 1H and 13C{1H} NMR spectroscopy, and HRMS. Single crystal structures of 1, 2, 4, and 5 reveal nearly square-planar geometry around Pd in each case. The PPh3/Hg poisoning and two-phase tests indicate that the catalysis is homogeneous for both the palladacycle and palladium complexes, probably through leaching of Pd0 from NPs in the case of the former. Catalysis of Suzuki coupling reactions with palladacycles (??0.001 mol-%) and palladium complexes (??0.01 mol-%) proceeds with and without nanoparticles.

Posted on 16 February 2015 | 4:50 pm


Preparation of Porous Silicon by Sodiothermic Reduction of Zeolite and Photoactivation for Benzene Oxidation

Porous silicon with its high specific surface, prepared by a sodiothermic reduction method using zeolite ZSM-5 as the silicon precursor, has been used as an efficient photoactivator for direct oxidation of benzene to yield phenol in H2O2 solution under visible light irradiation. The surface oxidation of the porous silicon together with electron transition under the visible light irradiation acts on the benzene molecules, resulting in the generation of phenol molecules. By acid treatment the photoactivity of the used porous silicon is regained. Porous silicon with its high specific surface, prepared by a sodiothermic reduction method using zeolite ZSM-5 as the silicon precursor, has been used as an efficient photoactivator for direct oxidation of benzene to yield phenol in H2O2 solution under visible light irradiation.

Posted on 13 February 2015 | 10:10 am


Formation of Cadmium Sulfide and Zinc Sulfide Mixture in the Interlayer Space of Montmorillonite

Cadmium sulfide and zinc sulfide (CdS and ZnS) were incorporated in sodium and cetyltrimethylammonium montmorillonites by the precipitation of sulfides from soluble metal sources in the presence of montmorillonites. The resulting hybrids were characterized by XRD, themogravimetric/differential thermal analysis (TG-DTA), TEM, Raman spectroscopy, and UV/Vis and photoluminescence spectroscopy. The absorption onsets owing to CdS and ZnS in cetyltrimethylammonium-montmorillonite appeared in a shorter wavelength region (311–520 nm) relative to that (309–484 nm) of the two semiconductors in sodium montmorillonite, thus reflecting the difference in the particle sizes of CdS and ZnS in the hybrids. The appearance of the broad emission bands combined with the bands centered at 469, 451, 440, and 431 nm owing to CdS and ZnS were attributed to the existence of both CdS and ZnS in the products. The difference in the emission intensity of the hybrids is discussed in terms of the role of the cetyltrimethylammonium cation. The unique optical properties of the two products were thought to occur through the interactions of sulfides with their environment (montmorillonite and cetyltrimethylammonium cation). A mixture of CdS and ZnS was prepared in unmodified and organically modified montmorillonite. The products showed emission bands owing to both CdS and ZnS. The blueshift of absorption onsets and the increase in PL intensity were caused by the confinement effect. CdS and ZnS formed separately in different interlayer spaces (segregation).

Posted on 13 February 2015 | 10:10 am


On the Iron(V) Reactivity of an Aggressive Tail-Fluorinated Tetraamido Macrocyclic Ligand (TAML) Activator

The electronic properties of iron tetraamido macrocyclic ligand (TAML) activators of peroxides can be finely and coarsely tuned by varying the substituents on the “head” and “tail” macrocyclic components, respectively. By examining the reactivity of the TAML oxidoiron(V) complex with head-NO2 and tail-F substituents, one is able to compare the impact of significantly reduced macrocyclic tetraamide donor capacity on fundamental processes such as hydrogen-atom abstraction, oxygen-atom transfer, and electron transfer by using prior studies with more electron-rich TAML systems. Herein, we demonstrate that the oxidoiron(V) form 3c can be generated by treatment of [Fe{4-NO2C6H3-1,2-(N2COCMe2N3CO)2CF2(Fe–N2)(Fe–N3)}(OH2)]– (1c) with m-chloroperoxybenzoic acid (mCPBA) in MeCN at –40 °C. The oxidation proceeds through the intermediacy of the ?-oxo[iron(IV)]2 dimer. The overall rate of the FeIIIFeV conversion by mCPBA is slightly faster for 1c than that of its less electron-rich precursor [Fe{C6H4-1,2-(N1COCMe2N2CO)2CMe2(Fe–N1)(Fe–N2)}(OH2)]– (1a). Nevertheless, the oxidative reactivity of 3c toward thioanisole and the hydrocarbons ethylbenzene and cyclohexane exceeds that of 3a by 4.3, 2.1, and 2.6 times, respectively. The reactivity of 3c is significantly greater towards ethylbenzene than that of the oxidoiron(V) species 3b derived from [Fe{C6H4-1,2-(N1COCMe2N2CO)2NMe(Fe–N1)(Fe–N2)}(OH2)]– (1b). The oxidation states of IV and V are achievable for electron-poor iron tetraamido macrocyclic ligand (TAML) activators. The corresponding oxidoiron(V) species demonstrates the highest reactivity reported so far for any TAML activator in the oxidation of thioanisole and C–H bond activations of ethylbenzene and cyclohexane.

Posted on 12 February 2015 | 7:10 pm


Microwave-Assisted Synthesis of Few-Layered TaTe2 and Its Application as Supercapacitor

We report a simple and rapid microwave-assisted synthesis of tantalum telluride (TaTe2) nanosheets. The ratio of tantalum pentachloride (TaCl5) and elemental tellurium (Te) powder were adjusted in the presence of NaBH4 in such a way as to obtain the TaTe2 nanosheet. The samples were characterized by various techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), UV/Vis spectroscopy, photoluminescence (PL) spectroscopy, and XRD. Our SEM, TEM, and AFM results show the formation of sheet-like morphology, while the XRD data confirms the high crystalline quality and stable phase of the TaTe2 formed. The supercapacitor cells were fabricated by using TaTe2 nanosheets as anode material, platinum metal wire as a counterelectrode, and Ag/AgCl as reference electrode. The calculated coulombic efficiency is more than 95?%, while the cycle-to-cycle decrease in capacity is less than 5?%. The maximum discharge or charging capacity is below 2.4 W?h/kg, which is an ideal characteristic for achieving supercapacitor behavior. The first experimental investigations on the use of microwave to synthesize atomically thin few-layer TaTe2 nanosheets are described. This material also shows good performance as a supercapacitor.

Posted on 12 February 2015 | 7:10 pm


Synthesis of CpM(CO)3–DAB and –PAMAM Dendrimer Conjugates and Preliminary Evaluation of Their Biological Activity

Dendrimers of different generations and core structures [diaminobutane poly(propylenimine) (DAB) G1, G2, G3; poly(amidoamine) (PAMAM) G1] were chosen as carriers for bioactive organometallic half-sandwich complexes of the type CpM(CO)3 (Cp = cyclopentadienyl, M = Mn or Re) to study the influence of these parameters on their biological activity against cancer cells. Structure–activity relationships were determined by variation of the metal center as well as the type, molecular weight, and number of terminal functional groups of the dendrimer conjugates. All conjugates were characterized by IR and NMR spectroscopy as well as HPLC. Their biological activity was determined on MCF-7 human breast cancer cells by the resazurin assay. Interestingly, the most-active compounds were the first-generation dendrimer conjugates. The Mn and Re series showed nearly the same activities. Thus, the cytotoxicity of the dendrimer conjugates does not seem to directly correlate with the type or number of terminal functional groups. Rather, it points to a mechanism of action that is different from that previously observed for peptide conjugates with similar CpM(CO)3 functional groups. Dendrimers of different generation and core structure are used as carriers for bioactive organometallic half-sandwich complexes of the type CpM(CO)3 (Cp = cyclopentadienyl, M = Mn or Re). Interestingly, the most-active compounds are the first-generation dendrimer conjugates, and the influence of the metal center is much less pronounced.

Posted on 12 February 2015 | 7:10 pm


Trinuclear Half-Sandwich RuII, RhIII and IrIII Polyester Organometallic Complexes: Synthesis and in vitro Evaluation as Antitumor Agents

Schiff base ligands obtained from the condensation of 4-aminophenylmethanol and either 2-pyridinecarboxaldehyde or salicylaldehyde were used to synthesise bidentate trimeric ester ligands. The trimeric ester ligands were used to prepare a new series of trinuclear polyester organometallic complexes by using the dimeric precursors, [Ru(?6-p-iPrC6H4Me)Cl2]2, [Rh(C5Me5)Cl2]2 or [Ir(C5Me5)Cl2]2. The Schiff base ligands act as bidentate donors to each metal. All compounds were characterised by NMR and IR spectroscopy, elemental analysis and EI/ESI mass spectrometry. Model mononuclear analogues were prepared, and the molecular structures of selected compounds were determined by single-crystal X-ray diffraction analysis. The mono- and trimeric ligands and the metal complexes were evaluated for inhibitory effects against the human ovarian cancer cell lines, A2780 (cisplatin-sensitive) and A2780cisR (cisplatin-resistant), and the model human skin fibroblast cell line, KMST-6. Polyester-containing trinuclear half-sandwich RuII, RhIII and IrIII complexes were prepared and characterised. The cytotoxicity was investigated for all compounds. Aqueous stability studies and interactions with model DNA 5?-GMP were performed for the most-active compounds.

Posted on 11 February 2015 | 4:50 pm


Spring-Loaded Iron(II) Complexes as Magnetogenic Probes Reporting on a Chemical Analyte in Water

A paramagnetic quality may be established in an aqueous sample if it contains a molecular probe that responds to the addition of a chemical analyte by turning from a diamagnetic state into a paramagnetic one (off–on). We explore here a stable, low-spin, binary iron(II) complex that stores so much potential energy that its transformation by the target analyte leads to its fragmentation into a high-spin complex despite the imposing strength of the chelate effect. The underlying ligand is a mixed aminal, the components of which can be freely varied to optimize response kinetics with the initial probe stability preserved. With decreasing leaving-group character of the azole component, the probe stability improves, and the response kinetics diminish. An optimal arrangement can be found with a pyrazole paired with an electron-deficient aromatic carbaldehyde component (nitro substitution). The drastic electronic reversion associated with the reduction of the nitro group to an amino group is the principal reason for the observation of an initially stable probe that suffers swift fragmentation when reacted with a reductive analyte. A new low-spin iron(II) triazacyclononane-based complex, selected from four different candidates, acts as a molecular probe that turns a diamagnetic aqueous sample into a paramagnetic one as a response to a chemical analyte. The four complexes are prepared by a highly convergent synthetic protocol and give precious insights into structure–activity relationship (SAR) tendencies.

Posted on 11 February 2015 | 3:51 pm


A Trinuclear AuI Complex with Different R3P–Au Centers: Synthesis, Characterization, and Synergetic Catalysis for Hydration of Phenylacetylene

A trinuclear AuI complex (3A) was synthesized and fully characterized relative to mononuclear (1A) and dinuclear (2A) complexes. The single-crystal X-ray diffraction analyses show that the AuI-centered vectors in each of the AuI complexes (1A–3A) are all in a slightly distorted linear configuration, in which the AuI center is diagonally coordinated by one Cl– and one phosphine ligand. In 3A each P–Au–Cl vector is radially attached to the core of 1-(thiazol-2?-yl)imidazolyl, which does not allow the short contact between the Au atoms to develop an aurophilic AuI–AuI interaction. Every P–Au–Cl moiety in 3A is different to each other in terms of Au–P and Au–Cl bond lengths, P–Au–Cl bond angles, and P–Au–Cl configurable orientation owing to the different coordinating ability of the involved phosphines. When 1A–3A were employed as the precatalysts for the hydration of phenylacetylene in aqueous methanol media without the involvement of any auxiliary additive, and at the same benchmark Au concentration, the reaction over 3A proceeded selectively according to Markovnikov's rule with the highest yield of acetophenone relative to those over 2A and 1A. This indicates that the catalytic performance of 3A is the outcome of the synergetic effect of the three different R3P–Au centers, in which each R3P–Au site plays an individual role in activating the substrate molecule. A trinuclear AuI complex of 3A was synthesized and fully characterized relative to the mononuclear (1A) and dinuclear (2A) complexes. Compound 3A exhibited the best catalytic performance for hydration of phenylacetylene owing to the synergetic catalytic effect of the three R3P–Au centers, in which each Au site acted in a different way to activate the substrate molecules.

Posted on 11 February 2015 | 3:50 pm


Intercalates of Strontium Phenylphosphonate with Alcohols – Structure Analysis by Experimental and Molecular Modeling Methods

Alcohol intercalated strontium phenylphosphonates were prepared by the addition of alcohols to an aqueous solution of strontium phenylphosphonate (SrPhP). These intercalates are unstable and de-intercalate spontaneously at ambient conditions. For the complete elucidation of their structure, a combination of a single-crystal X-ray diffraction and molecular modeling was used. The structure of the host layers in methanol (SrPhP·MeOH) and ethanol (SrPhP·EtOH) intercalates is composed of strontium atoms, which are eight-coordinate by oxygen atoms of the phosphonato groups and of water molecules. The structures of SrPhP·MeOH and SrPhP·EtOH differ in the orientation of the phenyl rings. The alcohol molecules reside in the cavities formed by the phenyl rings and are coordinated to the Sr atoms of the host layer through their oxygen atoms. On the basis of the structure of SrPhP·EtOH, the structures of propanol and butanol intercalates and of strontium phenylphosphonate dihydrate (SrPhP·2H2O) were modeled. The proposed model of SrPhP·2H2O, which features three kinds of water molecules, elucidates the temperature- and humidity-dependent behavior of the compound. Structures of alcohol intercalated strontium phenylphosphonates were suggested on the basis of a combination of single-crystal X-ray diffraction data and molecular modeling.

Posted on 11 February 2015 | 3:50 pm


Generation of Defect-Modulated Metal–Organic Frameworks by Fragmented-Linker Co-Assembly of CPO-27(M) Frameworks

The generation of defect-modulated metal–organic frameworks (MOFs) by the successful stepwise doping of 2-hydroxyterephthalate (BDC-OH) into frameworks of the CPO-27-M type is discussed. The influence of MgII, CoII, and NiII ions on the product formation has been investigated by powder XRD (PXRD), IR spectroscopy, and thermal analysis. To establish the successful incorporation of the fragmented linker molecule, 1H NMR spectra were recorded after the digestion of the MOFs in DCl/[D6]dimethyl sulfoxide. After the incorporation of BDC-OH, microporous structures were generated with reasonable porosity. The morphologies of the reaction products were checked by SEM measurements, and no significant changes to the morphologies were observed after the fragmented-linker doping. The generation of defect-modulated metal–organic frameworks (MOFs) by stepwise doping of 2-hydroxyterephthalate (BDC-OH) into CPO-27-M (M = MgII, CoII, and NiII) frameworks is discussed. Microporous structures are generated with reasonable porosity. No significant changes to the morphologies of the frameworks are observed after the fragmented-linker doping.

Posted on 11 February 2015 | 3:50 pm


Antimicrobial and Antitumor Activity of Enantiopure Pybox–Osmium Complexes

The antiproliferative activities of enantiopure (S,S)-iPr-pybox osmium(II) complexes {(S,S)-iPr-pybox = 2,6-bis[4?(S)-isopropyloxazolin-2?-yl]pyridine} against microbes and tumor cell lines (HeLa and HT29) as well as their interactions with plasmidic DNA have been studied. All of the analyzed compounds interacted in vitro with plasmidic DNA. They also interacted in vivo with microbes and tumor cell lines, as demonstrated by their interference with microbial growth and induction of apoptosis in HeLa cells. In particular, an IC50 value of 2.7?±?0.3 ?M has been found for trans-[OsCl2{(S,S)-iPr-pybox}(1-PhCH2-PTA)][Br] (PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane). All of the water-soluble complexes used in these studies have been synthesized in high yields and were fully characterized. The antiproliferative activities of new water-soluble osmium(II) complexes against microbes and tumor cell lines are studied. The IC50 value for trans-[OsCl2{(S,S)-iPr-pybox}(1-PhCH2-PTA)][Br] {(S,S)-iPr-pybox = 2,6-bis[4?(S)-isopropyloxazolin-2?-yl]pyridine, PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.13,7]decane} against HeLa cells is 2.7?±?0.3 ?M.

Posted on 9 February 2015 | 7:20 pm


Al3+-Ion-Triggered Conformational Isomerization of a Rhodamine B Derivative Evidenced by a Fluorescence Signal – A Crystallographic Proof

A newly designed rhodamine B anisaldehyde hydrazone exhibits Al3+-ion-induced cis (L) to trans (L?) conformational isomerization with respect to the xanthene moiety through a rotation about a N–N bond; the isomerization is indicated by a detectable naked-eye color change and a turn-on red fluorescence in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer (EtOH/Water 1:9 v/v; pH 7.4) at 25 °C. In support of this observation, detailed spectroscopic and physicochemical studies along with density function theory (DFT) calculations have been performed. This cis-to-trans conformational isomerization is due to Al3+ ion coordination, which induces this visual color change and the turn-on fluorescence response. To strengthen our knowledge of the conformational isomerization, detailed structural characterizations of the cis and trans isomers in the solid state were performed by single-crystal X-ray diffraction. To the best of our knowledge, this is the first structural report of both cis and trans conformational isomers for this family of compounds. Moreover, this noncytotoxic probe could be used to image the accumulation of Al3+ ions in HeLa and MCF-7 cell lines. A noncytotoxic rhodamine B anisaldehyde hydrazone exhibits an aluminium-ion-induced cis (L) to trans (L?) conformational isomerization with respect to the xanthene moiety through a rotation about a N–N bond; the change is signaled by a red fluorescence response.

Posted on 9 February 2015 | 7:10 pm


Alkynyl-Functionalized Imidazolium for “Click” Dendrimer Functionalisation and Palladium Nanoparticle Stabilization

Functionalization of imidazolium salts (IMSs) that allow easy derivation of molecular or solid supports are called for in various applications. Here, the synthesis of an alkyne-containing IMS can be achieved in three steps from 2,4,6-trimethylaniline, and this IMS can be further successfully functionalized by using either Sonogashira or a “click” CuAAC reaction that was applied to dendritic IMS synthesis giving high yields. Applications are illustrated for Pd nanoparticle stabilization by the IMS dendrimer for Suzuki–Miyaura catalysis. An imidazolium salt containing an alkynyl group was synthesized in three steps in order to functionalize nanomaterials by means of CuAAC and Sonogashira reactions. For instance, a nona-azido dendritic core could be “clicked” with the alkynyl-containing imidazolium salt. The resulting dendrimer allows the stabilization of palladium nanoparticles that are active in the Suzuki–Miyaura cross-coupling reaction.

Posted on 9 February 2015 | 7:10 pm


Homogeneity Range of the Zirconium Phosphide Telluride Zr2+xPTe2 and the High-Temperature Phase Transformation to Zr2PTe

The synthesis of the phosphide telluride Zr2+xPTe2 was accomplished by a solid-state reaction from the elements. Le Bail refinements of the data from the as-synthesized crystalline powders as well as the thermal decomposition of Zr2PTe2 along the homogeneity range Zr2+xPTe2 with the release of P4(g) and Te2(g) evidence a maximum zirconium content corresponding to the composition Zr2.5PTe2. The thermal decomposition product of Zr2.5PTe2 undergoes a phase transformation to “Zr2PTe”, which adopts the structural motif of the binary phases ZrTe and ZrTe2. The new phase “Zr2PTe” has a wide homogeneity range Zr2–xP1–yTe1+y and tolerates a deficit in the cation position and a mixed occupation of the anions. The composition of the crystalline decomposition product was determined to be Zr1.95P0.84Te1.16 by Rietveld refinement and by analysis of the elemental composition by inductively coupled plasma optical emission spectroscopy (ICP-OES). Zr1.95P0.84Te1.16 crystallizes in the hexagonal space group P63/mmc (no. 194) with lattice constants a = 3.8726(1) Å and c = 13.008(1) Å. Zr2PTe2 decomposes along a homogeneity range up to Zr2.5PTe2 by partial filling of the van der Waals gap in the Bi2STe2 structure type. In the consecutive high-temperature decomposition step, “Zr2PTe” is formed. The new phase adopts the structural motif of the binary phases ZrTe and ZrTe2 and tolerates a deficit in the cation position and a mixed occupation of the anions (Zr1.95P0.84Te1.16).

Posted on 9 February 2015 | 7:10 pm


Rare-Earth Metal Complexes with Terminal Imido Ligands

Imide complexes [(TptBu,Me)Y(=NC6H3Me2-2,6)(DMAP)] and [(TptBu,Me)Lu{=NC6H3(CF3)2-3,5}(DMAP)] were obtained by Lewis base induced methane elimination of the corresponding methyl/anilide complexes, which were synthesized from [(TptBu,Me)LuMe2] and [(TptBu,Me)YMe(GaMe4)], respectively. Terminal Ln=N bonding is evidenced by very short Ln–N distances [min. 1.993(5) Å] and almost linear Ln–N–C(aryl) bond angles. Lewis base induced methane elimination converts [(TptBu,Me)Ln(Me)(NHAr)] into mono-rare-earth metal imide complexes [(TptBu,Me)Ln(=NAr)(DMAP)]; terminal Ln=N bond formation is promoted by the superbulky ancillary TptBu,Me and corroborated by very short Ln–N bond lengths and almost linear Ln–N–C(aryl) bond angles (see structure; C gray, H white, N green, B pink, Lu magenta, F yellow green).

Posted on 9 February 2015 | 12:20 pm


Mitochondria-Targeting Photocytotoxic Ferrocenyl Conjugates of N-Alkylpyridinium Salts

Ferrocenyl (Fc) conjugates (1–3) of alkylpyridinium cations (E)-N-alkyl-4-[2-(ferrocenyl)vinyl]pyridinium bromide (alkyl = n-butyl in 1, N,N,N-triethylbutan-1-aminium bromide in 2, and n-butyltriphenylphosphonium bromide in 3) were prepared and characterized, and their photocytotoxicities and cellular uptakes in HeLa cancer and 3T3 normal cells were studied. The species with a 4-methoxyphenyl moiety (4) instead of Fc was used as a control. The triphenylphosphonium-appended 3 was designed for specific delivery into the mitochondria of the cells. Compounds 1–3 showed metal-to-ligand charge-transfer bands at ? ? 550 nm in phosphate buffered saline (PBS). The Fc+/Fc and pyridinium core redox couples were observed at 0.75 and –1.2 V versus a saturated calomel electrode (SCE) in CH2Cl2/0.1 M (nBu4N)ClO4. Conjugate 3 showed a significantly higher photocytotoxicity in HeLa cancer cells [IC50 = (1.3?±?0.2) ?M] than in normal 3T3 cells [IC50 = (27.5?±?1.5) ?M] in visible light (400–700 nm). The positive role of the Fc moiety in 3 was evident from the inactive nature of 4. A JC-1 dye (5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazolylcarbocyanine iodide) assay showed that 3 targets the mitochondria and induces apoptosis by the mitochondrial intrinsic pathway caused by reactive oxygen species (ROS). Annexin/propidium iodide studies showed that 3 induces apoptotic cell death in visible light by ROS generation, as evidenced from dichlorofluorescein diacetate assay. Compounds 1–3 exhibit DNA photocleavage activity through the formation of hydroxyl radicals. A ferrocenyl conjugate of an N-butylpyridinium salt with a pendant triphenylphosphonium moiety shows specific mitochondrial localization and remarkable visible-light-induced photocytotoxicity in HeLa cancer cells and is less toxic in normal 3T3 cells. The photoinduced cell death follows a mitochondria-mediated apoptotic pathway.

Posted on 5 February 2015 | 9:22 am


Fabrication of Single-Layer Graphitic Carbon Nitride and Coupled Systems for the Photocatalytic Degradation of Dyes under Visible-Light Irradiation

A coupled system for the photocatalytic degradation of rhodamine B (RhB) was realized by a CdS/SL g-C3N4 (SL g-C3N4 = single-layer graphitic carbon nitride) photocatalyst under visible-light irradiation. SL g-C3N4 was fabricated by the ultrasonic exfoliation of bulk g-C3N4. Two series of CdS/SL g-C3N4 and CdS/g-C3N4 photocatalysts with different CdS content were prepared by a hydrothermal process. The photocatalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), UV/Vis diffuse reflection spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and transient photocurrent measurements. Compared with those of pure bulk g-C3N4, CdS, and SL g-C3N4, the samples of the CdS/SL g-C3N4 photocatalyst series exhibited enhanced photocatalytic activities and excellent photostabilities under visible-light irradiation. With an optimum CdS content of 33.3?% and a reaction time of 120 min, the RhB degradation efficiency reached 99.55?% under visible-light irradiation. From a first-order model, the rate constant (k) of the 33.3?% CdS/SL g-C3N4 photocatalyst is up to 13.59, 6.10, and 4.54 times those of bulk g-C3N4, SL g-C3N4, and CdS, respectively. On the basis of the corresponding energy band positions, a mechanism for enhanced photocatalytic activity is proposed. Owing to the excellent performance of the CdS/SL g-C3N4 series, a visible-light-responsive and environmentally friendly photocatalyst for the degradation of dyes was obtained. A visible-light-responsive and environmentally friendly photocatalyst has potential applications in the removal of dyes from wastewater. The synergic effect of single-layer graphitic carbon nitride (g-C3N4) and CdS can effectively separate and transfer photoexcited carriers and is proposed to be responsible for the enhancement of the photocatalytic activity.

Posted on 5 February 2015 | 9:22 am


Slow Magnetic Relaxation in Pseudo-One-Dimensional 2p-4f Chains Involving ?–? Interactions

The reactions of the nitronyl nitroxide radical 2-(p-nitrophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NIT-PhNO2) with Ln(hfac)3 (hfac = hexafluoroacetylacetonate) afford two mononuclear lanthanide nitronyl nitroxide complexes [Ln(hfac)3(NIT-PhNO2)2]·0.5C7H16 [Ln = GdIII (1), DyIII (2)]. X-ray structural analysis shows that both complexes have a similar mononuclear structure, in which two NIT-PhNO2 radicals are bonded to the LnIII center as monodentate ligands through the oxygen atoms of the NO groups. Interestingly, those mononuclear units form a pseudo-one-dimensional chain structure through ?–? interactions. Direct current (dc) magnetic measurements show that there is ferromagnetic coupling between the lanthanide ion and the radical ligand for both complexes. Alternating current (ac) magnetic susceptibility studies reveal that the DyIII complex shows slow relaxation of magnetization in zero field, which is observed for the first time in a lanthanide–radical complex with a pseudo one-dimensional structure through ?–? interactions. Two lanthanide nitronyl nitroxide complexes with pseudo-one-dimensional chain structures have been obtained. The DyIII complex shows slow relaxation of magnetization, and this represents a new strategy toward Ln–radical single-chain magnets (SCMs).

Posted on 5 February 2015 | 9:22 am


[XeF5]+/Metal and [XeF5]+/Non-Metal Mixed-Cation Salts of Hexafluoridoantimonate(V)

New types of [XeF5]+ salts, i.e., NO2XeF5(SbF6)2 and XeF5[Cu(SbF6)3], are derived from reactions between XeF5SbF6 and NO2SbF6 or Cu(SbF6)2, respectively. The crystal structure of the former consists of [NO2]+ and [XeF5]+ cations and [SbF6]– anions. The main feature of the crystal structure of XeF5[Cu(SbF6)3] are rings of CuF6 octahedra that share apexes with SbF6 octahedra connected into an infinite tridimensional framework. This arrangement leads to the formation of cavities within which [XeF5]+ cations are located. Raman spectra of both [NO2]+/[XeF5]+ and [XeF5]+/Cu2+ mixed-cation hexafluorido-antimonates(V) are reported herein. NO2XeF5(SbF6)2 and XeF5[Cu(SbF6)3] are the first examples of [XeF5]+/metal and [XeF5]+/non-metal mixed-cation compounds. The crystal structure of NO2XeF5(SbF6)2 is composed of [NO2]+ and [XeF5]+ cations and [SbF6]– anions. In the crystal structure of XeF5[Cu(SbF6)3] the [XeF5]+ cations are located in cavities present in the tridimensional framework made up of CuF6 and SbF6 octahedra sharing joint apexes.

Posted on 5 February 2015 | 9:22 am


Complexation of Tetrakis(acetato)chloridodiruthenium with Naphthyridine-2,7-dicarboxylate – Characterization and Catalytic Activity

The reaction of calcium naphthyridine-2,7-dicarboxylate (Cadcnp) with Ru2(OAc)4Cl in water resulted in the formation of Ca[Ru2(dcnp)(OAc)3]2 (3). X-ray crystal structural analysis of 3 confirmed its molecular structure and showed that the calcium ion binds to the lateral carboxylate groups of four neighboring anionic units of [Ru2(dcnp)(?-OAc)3] and two acetone molecules to form a two-dimensional framework. The RuII–RuII valence state of the diruthenium core was supported by superconducting quantum interference device (SQUID) magnetometry [?eff (300 K) = 2.77 ?B]. Complex 3 appears to be an efficient catalyst for the oxidative cleavage of olefins in aqueous media under mild conditions. Typically, the reaction of pulegone with NaIO4 in water catalyzed by 3 (1 mol-%) at 45 °C afforded 3-methyladipic acid quantitatively. The reaction of calcium naphthyridine-2,7-dicarboxylate (Cadcnp) with Ru2(OAc)4Cl provides Ca[Ru2(dcnp)(OAc)3]2 as the exclusive product. The complex is catalytically active for the oxidative cleavage of olefins in aqueous media.

Posted on 3 February 2015 | 11:10 am


A Eu-Doped Y-Based Luminescent Metal–Organic Framework as a Highly Efficient Sensor for Nitroaromatic Explosives

By an isomorphous substitution strategy, a three-dimensional metal–organic framework (MOF), [Y1.8Eu0.2(PDA)3(H2O)1]·2H2O (1; PDA = 1,4-phenylenediacetate), has been synthesized by solvent-assisted liquid grinding and direct heating. Dehydrated 1 (1?) shows strong red photoluminescence through the antenna effect upon excitation at 240 nm. The red emissive property was used for the visual detection of nitroaromatic explosives in acetonitrile through luminescence quenching. Importantly, 1? exhibited high sensitivity towards the sensing of 2,4,6-trinitrophenol (TNP), 1,3-dinitrobenzene (DNB), 2,4-dinitrotoluene (DNT), 4-nitrotoluene (NT), and nitrobenzene (NB) at very low concentrations (0 to 20 ?M). The estimated KSV (quenching constant based on linear Stern–Volmer plots) values are in the range 15.9?×?104–1.1?×?104 M–1, which are amongst the highest values known for nitroaromatic-sensing materials. For 1?, sensing of TNP down to 23 ppb has been achieved. The luminescence of a three-dimensional metal–organic framework (MOF) with aromatic-ligand-sensitized Eu3+ activators is useful for sensing trace amounts of nitroaromatic explosives in solution through the quenching phenomenon.

Posted on 3 February 2015 | 11:10 am


Synthesis, Structure and Magnetic Properties of a 3D Manganese(II) Framework Featuring a Heptanodal Topology and Tube-in-Tube Dihelical Chains

The interaction of MnII ions with acetate in a chemical environment provided by a decomposition reaction of the Schiff base 2-(1-hydroxy-2-methylpropan-2-ylimino)-1,2-di-phenylethanone gave a 3D MnII framework [Mn5(?3-OH)2(CH3COO)8]·2CH3CH2OH (1). This was characterized by infrared spectroscopy, elemental analysis and powder X-ray diffraction patterns, and structurally determined by single-crystal X-ray diffraction analysis. The title compound features two kinds of unprecedented tube-in-tube dihelical MnII chains with opposite chiralities. They are alternatively arranged and bridged by MnII ions linked by acetate ions to form a 3D framework with a rare heptanodal topology. Magnetic studies revealed that compound 1 shows spin-canted and metamagnetic behavior. This work affords a synthetic strategy incorporating the decomposition reaction of a Schiff base which provides the chemical environment for another reaction and to direct the formation of the title compound and its crystals. The decomposition reaction of a Schiff base drives the formation of a rare 3D MnII framework, which features a heptanodal topology and alternately arranged tube-in-tube dihelical chains with opposite chiralities, as well as spin-canted and metamagnetic behavior.

Posted on 3 February 2015 | 10:40 am


Fundamental Aspects of Rare Earth Oxides­ Affecting Direct NO Decomposition Catalysis

The basic aspects of rare earth oxides (REOs) that affect their capacity for direct NO decomposition catalysis were investigated. A correlation between crystal structure and catalytic activity was found, which is related to the NO adsorption ability of the REOs. The crystal structure was the most important factor affecting direct NO decomposition over REOs, since the adsorption of NO was significantly dependent on the coordination environments of the rare earth cations within each crystal lattice. Among the REOs, cubic C-type oxides showed higher NO decomposition activities than those of the others. Within a series of C-type cubic REOs, the activity was typically dominated by the density of the surface basic sites, and the effects of particle morphology and lattice parameters were small. Among four fundamental factors (crystal structure, lattice parameters, particle morphology, and the density of basic sites), crystal structure is the aspect that most significantly affects direct NO decomposition activities of rare earth oxides (REOs), and the density of basic sites ranks second in importance to crystal structure.

Posted on 3 February 2015 | 10:40 am


Ionic Ferrocene-Based Burning-Rate Catalysts with Polycyano Anions: Synthesis, Structural Characterization, Migration, and Catalytic Effects During Combustion

Alkylferrocene-based burning-rate (BR) catalysts, have a high tendency to migrate during curing and storage due to their neutral and nonpolar nature. To overcome these drawbacks, fifteen novel ionic compounds, 1-(ferrocenylmethyl)imidazolium paired with polycyano anions, were synthesized and characterized. The structures of eleven of the compounds were confirmed by single-crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal space group I4(1)/a; 2, 12 and 15 crystallize in the monoclinic space group P21/c, and 3 in the monoclinic space group P21/n; 4, 6–8, 13 and 14 crystallize in the triclinic space group P$\bar {1}$. Cyclic voltammetry investigations suggested that most of the compounds exhibit quasireversible redox systems. Compounds 1–10 have high thermal stability (> 190 °C). Migration studies revealed that these compounds are low-migratory materials. The thermal degradation of ammonium perchlorate (AP), hexogen (RDX), and octogen (HMX) catalyzed by these compounds was evaluated by differential scanning calorimetry (DSC) and by thermogravimetric (TG) techniques. The results show that the decomposition peak temperature of AP shifts downwards dramatically and that the released heat of AP increases significantly with the new compounds as additives (5 wt.-%). Moreover, the ionic compounds exhibit significant effects on the thermal decomposition of RDX. The catalytic activities of the new compounds are higher than those of their nitrate and picrate analogues, which supports the conclusion that high nitrogen content in a ferrocene-based BR catalyst is favorable for its combustion catalytic activity. Fifteen polycyano-based ionic ferrocene compounds were prepared and structurally characterized. The compounds exhibit low migration tendency and highly catalytic effects on thermal decomposition of ammonium perchlorate (AP), hexogen (RDX), and octogen (HMX).

Posted on 30 January 2015 | 8:43 am


A Mn6 Cluster inside a Mn10 Wheel: Characterization of a Mn16-Oximate Complex Resulting from a Tetrazole-2-pyridylketoneoximate Ligand

A new Mn16 topology consisting of one hexanuclear {MnII2MnIII4} unit coordinated inside a decametallic {MnII6MnIII2MnIV2} wheel was synthesized from 2-pyridylcyanoxime and azido ligands. A new tetrazole-2-pyridylketoneoximate ligand was obtained in situ by cyclization of the cyano group and azide mediated by manganese cations. Tetrazole-2-pyridylketoneoximate, obtained by in situ cyclization of 2-pyridylcyanoximate and azide, was characterized in a Mn16 complex with an unprecedented topology formed by one hexanuclear {MnII2MnIII4} unit coordinated perpendicularly to a decametallic {MnII6MnIII2MnIV2} wheel.

Posted on 20 January 2015 | 10:30 am


Electrospinning of Ionogels: Current Status and Future Perspectives

Ionogels (IGs), also termed ion gels, are functional hybrid materials based on an ionic liquid (IL) and a polymeric, hybrid, or inorganic matrix. IGs combine the properties of the matrix such as mechanical strength with IL properties like high ionic conductivity, high thermal stability, or catalytic activity. IGs are thus attractive for many applications, but the vast majority of IGs made and published so far are bulk materials or dense films. Applications like sensing or catalysis, however, would benefit from IGs with high surface areas or defined surface morphologies or architectures. In spite of this, only relatively few examples of high-surface-area IGs have been made so far; this has mostly been achieved by electrospinning, which has proven to be a promising strategy towards advanced IGs. The current review discusses first developments and outlines the future potential of electrospun ionogels, predominantly from a materials and inorganic chemistry perspective. Spin it: Electrospinning is a useful and low-cost approach towards high-surface-area nanofibrous ionogels, that is, multifunctional hybrid materials based on ionic liquids, with tremendous application potential from catalysis to energy, healthcare, and beyond. The article provides an overview of the field and discusses the future potential of these promising materials.

Posted on 25 November 2014 | 12:10 pm


Two-Photon Absorption Properties of Eu3+-DPA-Triazolyl Complexes and the Derived Silica Nanoparticles Embedding These Complexes

Several complexes and silica-based nanohybrids of rare-earth ions (Eu3+, Gd3+) have been synthesized from dimethyl 4-azidopyridine-2,6-dicarboxylate (4) following the Click chemistry approach. A complete spectroscopic study indicates that such compounds exhibit strong sensitization by the antenna effect from both UV and NIR excitations. The Gd3+-based materials show phosphorescence under ambient conditions, which originates from the lowest-energy intra-ligand triplets. Fine analysis of the NIR excitation spectra using time resolved photoluminescence spectroscopy (TRS) indicates that the spectral repartition of the triplet T1 state differs notably between the complexes and the NPs embedding the complexes. Moreover the dependence of Eu3+ luminescence vs. incident beam power in the NIR region diverges from pure quadratic dependence expected in the framework of the two-photon absorption process. The results are discussed considering the occurrence of a direct singlet-to-triplet optical absorption transition (S0T1) upon NIR excitation. The TRS technique is used at 300 K to analyze the phosphorescence and the NIR excitation spectra of Gd3+-, Eu3+-DPA-triazolyl complexes and derived NPs embedding them. The TPA excitation spectra of the NPs are located on the low-energy side of the phosphorescence spectrum and consist of narrow bands attributed to the S0(0)T1(0–2) pure electronic transition.

Posted on 21 November 2014 | 3:20 pm


Glycine–Nitrate Process for the Elaboration of Eu3+-Doped Gd2O3 Bimodal Nanoparticles for Biomedical Applications

Monoclinic and cubic europium-doped Gd2O3 structures were selectively synthesized by the glycine–nitrate process by fine control of the synthesis temperature through the crucial fuel/oxidant ratio. The cubic phase is obtained under fuel-rich conditions, whereas stoichiometric conditions induce the simultaneous formation of cubic and monoclinic polymorphs. The samples were subjected to appropriate sintering to obtain highly crystalline and carbon-free materials. The average nanoparticle (NP) size determined by TEM for these nanopowders (23 nm) agrees with the average crystallite sizes obtained from XRD Rietveld analysis; therefore, the particles are monocrystalline. Both electron energy loss spectroscopy (EELS) and photoluminescence studies showed that the europium-doped NPs are highly luminescent, and the Eu3+ ions are homogeneously distributed over the whole material as well as over the two gadolinium crystallographic sites of the cubic phase. These fluorescent NPs exhibit relaxivities that define them as potential T1 contrast agents for further biomedical applications. By fine control of the flame temperature in the glycine–nitrate process, highly crystalline Eu3+-doped and undoped Gd2O3 nanoparticles are obtained. In the doped samples, the Eu3+ ions are homogeneously distributed over the whole material. The Eu:Gd2O3 NPs are highly luminescent and exhibit relaxivities that define them as potential T1 contrast agents for biomedical applications.

Posted on 18 November 2014 | 10:23 am


Molecular Mechanisms of [Bi6O4(OH)4](NO3)6 Precursor Activation, Agglomeration, and Ripening towards Bismuth Oxide Nuclei

Molecular dynamics simulations have been employed to characterize the role of [Bi6O4(OH)4](NO3)6 cage structures in DMSO solution as precursors to larger bismuth oxide aggregates. We find that the nitrate ions play a twofold role: (i) the association of [Bi6O4(OH)4](NO3)6 clusters – which are fully coordinated by six nitrate ligands – is electrostatically disfavored giving rise to stable [Bi6O4(OH)4](NO3)6 solutions; (ii) in contrast, the dissociation of a single nitrate ligand results in attractive cluster–cluster interactions. This results in the formation of oligomers, which are initially bridged by one to three nitrate ions, but then form Bi–O contacts by sharing common edges and faces and eventually ripen into nuclei of bismuth oxide. Strikingly, this process may be induced by a single activated species, the [Bi6O4(OH)4](NO3)5+ cluster, which may bind several [Bi6O4(OH)4](NO3)6 clusters. Molecular dynamics simulations unravel the early steps of bismuth oxide precursor association and ripening into larger aggregates. Nitrate ions play a twofold role in the process by preventing the association of Bi6O4(OH)4(NO3)6 clusters but at the same time inducing the formation of oligomers comprising under-coordinated Bi ions.

Posted on 13 November 2014 | 1:30 pm


Possible Roles of the Spatial Distribution of Organic Guest Species in Mesoporous Silicas to Control the Properties of the Hybrids

Mesoporous silicas are promising materials for the construction of host–guest hybrids by the accommodation of functional unit/guest species into the mesopore, and moreover, by hierarchical assembly with controlled location, density, and orientation. Precisely designed structures open up the versatile functions of mesoporous silicas and their host–guest systems. In this microreview, the spatial distribution (location, density, and orientation) of the organic functional units/guest species in mesoporous silicas (mainly one-dimensional cylindrical) is discussed to highlight the present status of the host–guest chemistry of mesoporous silicas. The spatial distribution (location, density, and orientation) of the functional units (guest species) attached/included on/in mesoporous silicas are discussed to highlight the status of the host–guest chemistry of mesoporous silicas.

Posted on 12 November 2014 | 12:40 pm


Synthesis of Advanced Nanoreinforced Polyurethane with Thiolene Photografted Organo-Modified Layered Double Hydroxide

New bionanocomposites with strongly intertwined structures based on polyurethane and layered double hydroxides (LDH) were obtained by using two different intermolecular thiolene coupling strategies in which the modification of LDH with oleic acid was either performed first and then followed by the thiolene photografting using 2-mercaptoethanol, or the initial thiolene photografted oleic acid/2-mercaptoethanol product was subsequently used to modify the LDH platelets. The resultant photografted oleate/LDH was condensed with diisocyanate and the addition of poly(ethyleneglycol) yielded a final hybrid polymer. The interleaved LDH materials were characterized by X-ray diffraction and thermogravimetric analysis, underlining the possible commutative steps between photografting and organo-modification processes. The resultant polyurethanes were characterized by FTIR spectroscopy, nuclear magnetic resonance, differential scanning calorimetry and rheology. Furthermore, the durability of the resultant polymers was assessed by photo-FTIR. The results showed that strongly intermingled polyurethanes were processed by both strategies. Enhanced mechanical properties as well as more prolonged durability were found after anchoring LDH sheets and this was even more amplified when using the photografted acid direct intercalation into the LDH during the first synthesis step. Successive processes to yield layered double hydroxide filled polyurethane nanocomposite including (1) organo-modification of LDH platelets, (2) functionalization using UV thiolene coupling and (3) monomer addition.

Posted on 12 November 2014 | 12:40 pm


Hybrid Polymer Electrolytes Based on a Poly(vinyl alcohol)/Poly(acrylic acid) Blend and a Pyrrolidinium-Based Ionic Liquid for Lithium-Ion Batteries

Polymer blends of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) were prepared with different molar ratios by a solvent-casting technique. The XRD patterns of the blends show that the degree of crystallinity of the PVA membranes decreases with the addition of PAA owing to the formation of interpenetrating polymer chains. The vibrational spectra of the blend membranes reveal the formation of strong hydrogen bonding between PVA and PAA. Dynamic mechanical analysis (DMA) reveals that the storage modulus of a 25 mol-% PAA sample is comparable to that of pure PVA and, therefore, confirms the mechanical stability of the blend membranes. Significant changes in the peak areas and chemical shifts of the PVA hydroxyl signal (? = 4–5 ppm) in the 1H NMR spectra of the blend membranes confirm the strong hydrogen bonding between the OH groups of PVA and PAA. The ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) with 0.2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was added to the polymer blend to prepare flexible, nonvolatile hybrid polymer electrolytes for lithium-ion batteries. A maximum ionic conductivity of 1 mS?cm–1 is observed at 90 °C for the membrane with 70 mol-% IL. Mechanically stable polymer membranes for lithium-ion batteries consist of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR14TFSI) doped with 0.2 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

Posted on 11 November 2014 | 2:10 pm


Ionic Liquid Based Approaches to Carbon Materials Synthesis

Ionic liquids (ILs) have attracted continuous interest because of their remarkable physicochemical properties, including high thermal and chemical stability, nonflammability, negligible vapor pressure, designable cation/anion pairs, electrical and ionic conductivity, low melting points, and affinity towards many compounds. These properties make ionic liquids valuable in the creation of new materials and new processes throughout almost the entire field of materials chemistry. An emerging field is the use of ionic liquids in carbon-based nanomaterials. Initially, ionic liquids were used as self-templating carbon sources for the generation of unusual carbon materials in which homogeneous heteroatom doping (e.g., N, B, S) can be accomplished fairly easily. Later, ionic liquids were recognized as suitable for use in the conversion of biomass into porous carbon materials, acting as both reaction media and porosity-directing regulator. Such applications open the door towards the synthesis and accurate tuning of carbon nanostructures, for example, pore structure, morphology, heteroatom doping, and surface functionality. In addition, the hybridization of ionic liquids and nanocarbons enables the development of composites by combining the properties of the ionic liquid (e.g., ionic conductivity or catalytic activity) and those of a host (e.g., chemical or mechanical stability). Currently, although the research of this topic is rapidly expanding, the rational design and synthesis of carbon-based materials, particularly their applications in energy storage and transformation, is still in its infancy. In this review, we focus on several aspects of ionic liquid derived carbons with the aim of shedding light on this new topic: 1) Ionic liquids as an advanced medium for carbon synthesis, 2) ionogels derived from nanocarbon, 3) ionic liquids as fluid precursors for functional carbons, and 4) ionic liquid derived carbons for heterogeneous catalysis. Ionic liquids are currently established solvents, precursors for carbon materials, and components of carbon-based ionogels. The unique properties of ionic liquids are beneficial for the formation of unusual carbon materials or composites with homogeneous heteroatom doping (e.g., N, B, S) and controllable porosity.

Posted on 14 October 2014 | 2:40 pm


Preparation of Alginate/Graphene Oxide Hybrid Films and Their Integration in Triboelectric Generators

Sodium alginate/graphene oxide (Al/GO) nanocomposite films were prepared by solvent casting. The structure, morphology, and electrical properties of Al/GO films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and thermal analysis. The utilization of such an Al/GO film for a device that uses friction as the charging process to convert mechanical energy into electric power is reported. The triboelectric generator (TEG) was fabricated by stacking a drop-cast Al/GO film bewteen indium–tin oxide (ITO)-coated poly(ethylene terephthalate) (PET) and a PET sheet. Furthermore, the utilization of such a TEG as a pressure sensor is also illustrated. Sodium alginate/graphene oxide nanocomposite films were prepared by a solvent-casting method. We report the proof of concept that such a hybrid system can be used as the active component of a triboelectric generator. The involvement of a biodegradable polymer might introduce new applications in biodegradable/biocompatible electronics.

Posted on 6 October 2014 | 11:10 am


Nanostructuring of Bridged Organosilane Precursors with Pendant Alkyl Chains

The copper-catalyzed alkyne azide cycloaddition (CuAAC) reaction was combined with sol-gel reactions for the production of bridged silsesquioxanes (BSs) in which hexyl and icosanyl chains are pendant and anchored on a single position to a triazole ring. The influence of the alkyl chain length on the structure of the BSs, represented by the notation Cn/siloxane (where n = 6 and 20), was examined. The C20/siloxane hybrid is a hydrophobic material that exhibits a hierarchically structured lamellar bilayer organization, a texture composed of microplates of nanometer thickness, and a reversible time-independent order/disorder phase transition (onset at 60 °C). The driving forces for self-assembly are van der Waals interactions between the icosanyl chains and ?-? interactions between the triazole rings. In the essentially amorphous C6/siloxane hybrid, the latter contribution promotes the genesis of a pre-lamellar phase similar to that found in C20/siloxane. A new bridged silsesquioxane with hierarchically structured lamellar bilayer structure and a texture composed of microplates of nanometer thickness was obtained by sol-gel and self-assembly by using a bridged organosilane carrying a pendant icosanyl chain produced by click chemistry. The hybrid exhibits a time-independent reversible order/disorder phase transition in a heating-cooling cycle.

Posted on 1 October 2014 | 7:23 pm


Constitutional Hybrid Materials – Toward Selection of Functions

This microreview reveals a new strategy to transcribe supramolecular architectures in self-organized constitutional hybrids. In particular, the use of communicating reversible-covalent and supramolecular hydrophobic interfaces between organic/supramolecular and inorganic/siloxane networks represents a useful approach for improving their compatibility. Interpenetrated hybrid components lead, after the sol–gel process, to materials in which the features of supramolecular and inorganic networks are expressed through cross-over and linear processing schemes. Such a “dynamic marriage” between the processes of supramolecular self-assembly and inorganic sol–gel polymerization, which communicate synergistically, leads to higher self-organized hybrid materials on increased micrometric scale. Considering the simplicity of this strategy, possible applications in membranes and sensors are effective, reaching close to novel expressions of complex matter. This review will focus on the implementation of constitutional dynamic chemistry (CDC) toward constitutional hybrid materials, emphasizing recent developments in biomimetic ion channels, membranes, and constitutional hybrid materials.

Posted on 29 September 2014 | 11:30 am


Conformational Changes and Phase Behaviour in the Protic Ionic Liquid 1-Ethylimidazolium Bis(trifluoromethylsulfonyl)imide in the Bulk and Nano-Confined State

We report a Raman spectroscopic study of conformational changes to the TFSI anion in the protic ionic liquid 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, [C2HIm][TFSI], in its bulk and nano-confined state. We show that the TFSI anion is found as a mixture of cis and trans conformations at room temperature and in the liquid state, whereas this equilibrium shifts towards an increased cis population upon confinement in silica. In addition, the strong Raman signature at ca. 743 cm–1 assigned to TFSI is found at systematically higher frequencies in the confined state. These findings suggest a higher packing efficiency, or density, for the ionic liquid at the silica surface. Moreover, the enthalpy of conformational change is only marginally affected upon confinement (4.32?±?1.30 vs. 5.27?±?1.09 kJ?mol–1), and the entropy is found to be a few J?mol–1?K–1 higher in the confined state. Raman spectra recorded upon heating from very low temperatures show that the phase behaviour of the ionic liquid is also affected by confinement, with crystallization upon cooling being frustrated in favour of an amorphous glassy phase. To summarize, our results indicate that the interaction established in the ionogels between the silica surface and the protic ionic liquid [C2HIm][TFSI] favours local structural disorder, in conceptual agreement with the slightly higher experimentally estimated entropy. Conformational changes of the TFSI anion in the protic ionic liquid C2HImTFSI have been monitored by temperature-dependent Raman spectroscopy for the bulk and nano-confined states. Phase behaviours have also been spectroscopically investigated at a range of temperatures. In the nano-confined state the cis form predominates and the enthalpic term was higher.

Posted on 29 September 2014 | 11:30 am


Organic–Inorganic Hybrid Membranes Based on Sulfonated Poly(ether ether ketone) and Tetrabutylphosphonium Bromide Ionic Liquid for PEM Fuel Cell Applications

Ionic liquids (ILs), with their inherent ionic conductivity and negligible vapor pressure, can be exploited in proton exchange membrane (PEM) fuel cells for which thermal management is a major problem and the cell operation temperature is limited by the boiling point of water. In this work, sulfonated poly(ether ether ketone) (SPEEK) membranes were modified by the incorporation of tetrabutylphosphonium bromide ([P4 4 4 4]Br) by solvent-casting. Electrochemical impedance spectroscopy (EIS) was used to study the electrical properties of the modified membranes. Simultaneous TGA and FTIR studies were used to evaluate the thermal stability and chemical structure of the modified membranes, respectively. 1H NMR spectroscopy was applied to probe the changes in the chemical environment due to the interaction between the ionic liquid and the polymer. Mechanical properties were studied by dynamic mechanical analysis. The temperature-dependent behavior of the viscosity of the [P4 4 4 4]Br ionic liquid was observed to obey the Vogel–Fulcher–Tammann (VFT) equation, and was correlated to the ion-conducting properties of the IL-doped SPEEK membranes. Polymer–ionic liquid electrolyte membranes were fabricated from tetrabutylphosphonium bromide ([P4 4 4 4]Br) and sulfonated poly(ether ether ketone) (SPEEK). Their thermal, mechanical, structural and electrical properties show promise for their use in high-temperature fuel cell applications.

Posted on 19 September 2014 | 10:20 am


Prospective Electroluminescent Hybrid Materials

Tris(8-hydroxyquinoline)boron (Bq3) was synthesized by means of a high-temperature substitution reaction. Mixtures of different Bq3 polymorphs were obtained and their spectral and structural properties were investigated. A comparison of organic light-emitting diode (OLED) structures with Bq3 and Alq3 as emitting materials showed the prospective application of Bq3 as a blue-light emitter. Thin-film hybrid materials (HM) were made by vacuum thermal deposition. HM films were produced by layer-by-layer thermal vacuum sputtering of B2O3/Alq3/B2O3/MoO3/Al on a glass substrate with an indium tin oxide (ITO) conducting layer. The HM films were locally heated by a diode laser (785 nm). The pumping of 150 W?cm–2 energy for one second resulted in an irreversible change in the HM film. Chromaticity coordinates for the as-prepared and laser-induced HM films showed a significant difference in their photoluminescent properties. Three polymorphs of tris(8-hydroxyquinoline)boron (Bq3) were obtained by high-temperature substitution reaction. Their spectral and structural properties were investigated and showed Bq3 to be a potential blue emitter. Hybrid material (HM) films B2O3/Alq3/B2O3 on a glass substrate were made by vacuum sputtering. Laser heating of the HM film resulted in an irreversible change in its photoluminescence.

Posted on 12 September 2014 | 10:10 am


Spatially Confined Functionalization of Transparent NiO Thin Films with a Luminescent (1,10-Phenanthroline)tris(2-thenoyltrifluoroacetonato)europium Monolayer

Transparent MOCVD-grown NiO films have been functionalized with the luminescent (1,10-phenanthroline)tris(2-thenoyltrifluoroacetonato)europium(III) complex [Eu(TTA)3phen] by combining sputter activation with a solution synthetic route. To introduce the Eu complex only on selected regions, some areas of the NiO surface were activated by Ar+ ion sputtering and then functionalized with 3-phosphonopropionic acid (CPPA) followed by the anchoring of Eu(TTA)3phen through a ligand-exchange reaction between ?-diketonato ligands and the carboxylic groups of CPPA. The functionalized material was characterized by X-ray photoelectron, UV/Vis and luminescence spectroscopy. XPS measurements indicated that CPPA prefunctionalization and, in turn, the Eu(TTA)3phen anchoring occurs only on the sputter-activated region, while no anchoring takes place on the unactivated surface. The optical properties of the Eu(TTA)3phen–NiO system were evaluated by UV/Vis and luminescence spectroscopy. Anchoring of the Eu(TTA)3phen complex on MOCVD-grown NiO films is reported. The NiO surface was activated by means of a sputtering process and functionalized with a phosphonic linker, followed by the coordination of the Eu complex through a ligand-exchange reaction. The luminescent hybrid system has been proven to retain the optical properties of the Eu complex.

Posted on 12 September 2014 | 10:10 am


Furan-Modified Spherosilicates as Building Blocks for Self-Healing Materials

Octafunctional spherosilicates were used to prepare self-healing hybrid materials. The hydrosilation of the octakis(hydridodimethylsiloxy)-substituted spherosilicate with furfuryl allyl ether generates an inorganic nano-building-block that is used to formulate various self-healing hybrid materials based on a reversible Diels–Alder reaction. Curing with a molecular bismaleimide results in a hard, glassy but reversibly cross-linkable hybrid material. The reversibility of the curing mechanism allows the preparation of films with a heated press, which also opens the possibility to process the materials by injection molding. Substitution of the molecular cross-linker with an oligomeric poly(dimethylsiloxane) bismaleimide results in an elastomeric material. The kinetics of the Diels–Alder reaction upon cooling after a retro-Diels–Alder reaction are mainly controlled by the mobility of the cross-linker within the system. Octameric furfuryl-functionalized spherosilicates were used to prepare self-healing hybrid materials based on a reversible Diels–Alder reaction. Two different bismaleimides were used as dienophilic cross-linkers for the self-healing materials. The healing abilities are dictated by the nature of the cross-linker.

Posted on 9 September 2014 | 10:20 am


Coordination Polymers Based on Alkylboronate Ligands: Synthesis, Characterization, and Computational Modelling

Boronate ligands [R–B(OH)3–] have recently started to attract attention for the elaboration of coordination polymer networks. Here, three new crystalline structures involving butyl- and octylboronate ligands are described: Sr[Bu–B(OH)3]2, Ca[Oct–B(OH)3]2 and Sr[Oct–B(OH)3]2 (Bu = C4H9, Oct = C8H17). All were obtained as microcrystalline powders, and their structures were solved by synchrotron powder X-ray diffraction. IR and multinuclear (13C, 11B, 43Ca, 87Sr and 1H) solid-state NMR characterizations were performed on the materials. Computational models of the new Sr[Bu–B(OH)3]2 phase and the previously reported Sr[Ph–B(OH)3]2·H2O structure were then developed. The IR O–H stretching modes and NMR parameters were calculated for these models and are discussed in view of the experimental spectra. This work confirms the importance of computational studies on boronate phases to determine the nature of the H-bond network within the materials and to better understand their spectroscopic signatures. The synthesis and characterization of three new crystalline alkylboronate structures are described, together with their DFT modelling and calculations of solid-state NMR parameters and IR O–H stretching frequencies.

Posted on 9 September 2014 | 10:20 am


Modelling the Luminescence of Phosphonate Lanthanide–Organic Frameworks

The suitability of the computer package LUMPAC to calculate the photoluminescence properties of metal–organic frameworks was assessed by considering three systems based on the ditopic 1,4-phenylenebis(methylene)diphosphonic acid (H4pmd) ligand and Ln3+ ions, namely, [Eu(Hpmd)(H2O)] (1), [La2(H2pmd)(pmd)(H2O)2] (2) and [La2(H2pmd)3(H2O)12] (3, previously reported) and their isotypical materials doped with Eu3+ cations, [(La0.95Eu0.05)2(H2pmd)(pmd)(H2O)2] (4) and [(La0.95Eu0.05)2(H2pmd)3(H2O)12] (5). These materials were prepared, and their structures and luminescence properties were characterized. A straightforward approximation based on the simple crystallographic structural subunits of these materials was used and resulted in an excellent agreement between the calculated and experimental properties. The intramolecular energy transfer and back-transfer rates were predicted, and the T1??5D1 channel was shown to be the dominant pathway (9.03?×?104 s–1 for 1, 1.06?×?104 s–1 for 4 and 2.18?×?105 s–1 for 5). The applicability of the LUMPAC software for calculations of the photoluminescence properties of metal–organic frameworks is assessed by considering three systems with a ditopic 1,4-phenylenebis(methylene)diphosphonic acid ligand and Eu3+ ions. A simple method based on the crystallographic structural subunits affords excellent agreement between the calculated and experimental photoluminescence.

Posted on 4 September 2014 | 1:23 pm


Efficient Hybrid-Type CO2 Adsorbents of Reassembled Layered Double Hydroxide 2D Nanosheets with Polyoxometalate 0D Nanoclusters

Porous nanohybrids of cationic Mg-Al-LDH 2D nanosheets and anionic polyoxometalate (POM, V10O286– and W7O246–) 0D nanoclusters are synthesized by an exfoliation–reassembling process. The electrostatically derived reassembling between two kinds of nanostructures yields a layer-by-layer-ordered intercalation structure with porous structures composed of mesopores and micropores. The hybridization with POM leads to the remarkable enhancement of CO2 adsorption capacity (adsorptivity) of Mg-Al-LDH by about 10-fold. Of prime importance is that the CO2 adsorptivity of the nanohybrid is strongly dependent on the type of guest POM species, strongly suggesting that the CO2 adsorptivity of the LDH-based nanohybrid materials can be optimized by ones selection of guest species. The present study clearly demonstrates that the exfoliation–reassembling method is quite effective at enabling synthesis of new LDH nanosheet-based hybrid materials with improved CO2 adsorption capabilities. Porous nanohybrids of Mg-Al-layered double hydroxide (LDH) 2D nanosheets and polyoxometalate 0D nanoclusters are synthesized by an exfoliation–reassembling process. The resulting nanohybrid materials show promising CO2 adsorption capabilities exceeding those of pristine Mg-Al-LDH, underscoring the usefulness of the present hybridization method in optimizing gas adsorption by LDH materials.

Posted on 4 September 2014 | 1:20 pm


Properties of an Indium Tin Oxide Electrode Modified by a Laser Nanostructured Thin Au Film for Biosensing

Structural, optical, and electrochemical characteristics of the indium tin oxide (ITO) electrode modified by Au nanoparticle (NPs) produced by pulsed UV laser irradiation of thin films are investigated in this work. Properties of the NP arrays depend on the film thickness and parameters of the laser interaction. Semi-regular structures characterized by broad size distributions of mean values ca. 62–92 nm are observed in the SEM images. In absorbance spectra the plasmon resonance peaks located around 544 nm reveal an IR shift and an increase of damping of the plasmonic enhancement with increasing NP size. Despite the broad size distribution and negative effect of damping that results in plasmon decay times of below 3.2 fs, the ITO electrode modified by Au NP arrays shows marked improvement of the electrochemical activity towards the Fe2+/Fe3+ redox couple and also glucose. Results obtained for non-enzymatic glucose detection indicate the potential for cost-effective solutions in the area of biosensing. Thin Au films on ITO that were stepwise patterned by means of nanosecond UV laser pulses transformed into semi-regular nanoparticle arrays. The modified electrode showed enhanced activity towards ferricyanide redox systems as well as glucose, and can be considered for the production of a non-enzymatic biosensor.

Posted on 21 August 2014 | 12:13 pm


Optical and Electrooptical Properties of Porous-Silicon/Conjugated-Polymer Composite Structures

We report on the fabrication and characterization of porous-silicon/conjugated-polymer hybrids, created by combining a host columnar matrix of mesoporous silicon and a network of organic nanowires made from poly(N-vinylcarbazole) (PVK). A uniform and homogeneous filling of the pores by the polymers was accomplished by electrochemical polymerization of organic monomers inside the pores by using cyclic voltammetry. Spectroscopic measurements showed that polymerization inside the confined environment of the nanometric pores results in a tighter and denser packing of the polymer due to a change of the polymerization process from the vinyl groups to the conjugated carbazole groups, giving rise to a redshift of the absorption spectra and better electrical conductivity. Current-voltage characterization of the hybrids under dark conditions and under illumination were investigated. We demonstrate a simple method to control the band alignment between the organic polymer and the porous silicon, altering it from a type-I to a type-II interface by changing the doping polarity of the silicon substrate (from p-type to n-type, respectively). An efficient photoinduced charge separation was observed for the type-II interface (n-type porous-silicon–polymer interface), while no such effect was observed for the type-I organic–inorganic interface. An organic–inorganic hybrid structure consisting of porous silicon and nanowires of poly(N-vinylcarbazole) (PVK) exhibits optical behavior of the PVK nanowires, which is unique when compared with the bulk material. Furthermore, a simple method to control the band alignment between type-I and type-II is demonstrated. Our results enable a variety of applications and electrooptical characteristics.

Posted on 15 August 2014 | 11:20 am


Sulfonated Polymethylsiloxane as an Additive for Selective Calcium Oxalate Crystallization

Sulfonated and fluorescent polymethylsiloxanes (SO3H-PMS) were synthesized, and their effect as additives on in vitro calcium oxalate (CaOx) crystallization was evaluated. SO3H-PMS was prepared by hydrosilylation and sulfonation reactions with poly(dimethylsiloxane-co-hydrogenmethylsiloxane) (PDMS-co-PMHS). Several analytical tools were used to investigate the morphology, crystal structure, and chemical contents of the harvested CaOx crystals. Varying the concentration of SO3H-PMS induces a transition of CaOx monohydrate (COM) with expanded multilayer and circular stacked-sheet morphologies as well as of the bipyramidal CaOx dihydrate (COD) crystals in three crystallization procedures. Energy-dispersive X-ray spectroscopy (EDS) and XRD allowed detecting the presence of Si (0.2–1.0°wt.-%), which stems from SO3H-PMS adsorbed on CaOx, and the selective formation of phases of COM and COD. We demonstrated that the presence of anionic moieties on the SO3H-PMS backbone and their concentration were crucial to control the crystal type, morphology, crystal size, and chemical composition. Sulfonated and fluorescent polymethylsiloxanes (SO3H-PMS) were synthesized and used as additives for in vitro calcium oxalate (CaOx) crystallization. The strong modifying capacity of SO3HPMS on CaOx morphologies and CaOx monohydrate (COM) and CaOx dihydrate (COD) crystal types was demonstrated. Fluorescent CaOx crystals were also produced by the inclusion of SO3H-PMS into the CaOx matrix.

Posted on 27 June 2014 | 11:10 am


A Neutral 1D Coordination Polymer Constructed from the NiII Complex of the N-Phosphorylated Thiourea PhNHC(S)NHP(O)(OPh)2 and Pyrazine: A Single-Source Precursor for Nickel Nanoparticles

The N-phosphorylated thiourea PhNHC(S)NHP(O)(OPh)2 (HL) was synthesized by the reaction of PhNH2 and (PhO)2P(O)NCS. Reaction of the KL salt, generated in situ, with NiCl2 leads to pale violet [NiL2] with a 1,3-N,S- coordination mode of the ligands. Interaction of [NiL2] with pyrazine (pz) yields the 1:1 coordination polymer [NiL2pz]n. An unexpected change in the coordination mode of the phosphorus-containing ligands L from 1,3-N,S- to 1,5-O,S- was found in [NiL2pz]n upon coordination of additional donor ligands. [NiL2pz]n dissolved in tri-n-octylphosphine (TOP) was decomposed in hot hexadecylamine to give capped face-centered cubic Ni nanoparticles with an average particle size of 17(2) nm. Interaction of [Ni{PhNHC(S)NP(O)(OPh)2}2] with pyrazine (pz) yielded the 1:1 coordination polymer [NiL2pz]n, in which the coordination mode of L changed unexpectedly from 1,3-N,S- to 1,5-O,S-[NiL2pz]n dissolved in tri-n-octylphosphine (TOP) is decomposed in hot hexadecylamine to give TOP-capped face-centered cubic Ni nanoparticles with an average particle size of 17(2) nm.

Posted on 3 June 2014 | 5:10 pm





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