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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:

Synthesis of RhIII Anilido, Hydroxide, and Methoxide Complexes

The octahedral RhIII complexes [(tbpy)2Rh(XH)2][OTf]3 (tbpy = 4,4?-di-tert-butyl-2,2?-bipyridyl; X = NHPh or OH; OTf = trifluoromethanesulfonate), [(tbpy)2Rh(X)2][OTf] (X = NHPh or OH), [(tbpy)2Rh(NHPh)(NH2Ph)][OTf]2, [(tbpy)2Rh(Me)(NH2Ph)][OTf][BAr?4] (BAr?4 = tetrakis[(3,5-bis-trifluoromethyl)phenyl]borate), [(tbpy)2Rh(Me)(NHPh)][BAr?4], [(tbpy)2Rh(OMe)(Cl)]Cl, and [(bpy)Rh(X)2][PF6] (bpy = 2,2?-bipyridyl; X = OH, OMe) have been synthesized and characterized by 1H, 13C{1H}, and 19F NMR spectroscopy, elemental analysis, or high-resolution mass spectrometry as well as single-crystal X-ray diffraction for some complexes. A comparison of the solid-state structural data for [(tbpy)2Rh(Me)(NH2Ph)]2+, [(tbpy)2Rh(NH2Ph)2]3+, [(tbpy)2Rh(NHPh)2]+, and [(tbpy)2Rh(NHPh)(NH2Ph)]2+ is included. Octahedral and d6 complexes with ?-donating ligands often exhibit interesting reactivity. Herein, new examples of RhIII complexes with ?-donating anilido, hydroxide, and methoxide ligands are reported.

Posted on 30 January 2015 | 8:43 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

Copper(II) Complexes of 2,2?:6?,2?-Terpyridine Derivatives for Catalytic Aerobic Alcohol Oxidations – Observation of Mixed-Valence CuICuII Assembles

The reactions of copper(II) salts with simple terpyridine (tpy) ligands gave mononuclear monoligand complexes 1–3, of which two new structures have been characterized by X-ray crystallography. These complexes were applied as catalysts for the oxidation of benzylic alcohol to benzaldehyde in air in the presence of the radical 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Copper complexes 1 and 2 are efficient catalysts for the reactions in water at 70 °C with 4-dimethylaminopyridine (DMAP) as an extra base. The influence of TEMPO on the formation of new reactive intermediates during the catalytic reactions was tentatively investigated by introducing TEMPO into the reaction solutions of tpy derivatives with copper dichloride. Two new complexes with interesting solid-state structures resulting from these reactions have been isolated and characterized. The coordination reactions in the presence of TEMPO led to new mixed-valence CuICuII supramolecular assembles (4 and 5), although they adopt either discrete complex or 1D polymeric structures. Further catalytic studies indicated that the mixed-valence assembles 4 and 5 displayed higher catalytic activity than those of the mononuclear complexes under milder conditions. The relationship between the molecular structures of diverse copper complexes and their reactivity is discussed on the basis of the results obtained. Copper complexes based on terpyridine (tpy) derivatives have been synthesized and structurally characterized. The catalytic aerobic oxidations of alcohols in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) were investigated in water, and mixed-valence CuICuII assembles are more active catalysts than mononuclear CuII complexes.

Posted on 29 January 2015 | 1:40 pm

Synthesis, Crystal Structures, and Magnetic Properties of Heterodimetallic RuIII–3d Coordination Compounds Based on a Meridional Tricyanoruthenium(III) Building Block

The synthesis, crystal structures, and magnetic properties of three cyano-bridged heterodimetallic compounds prepared from the paramagnetic RuIII building block mer-[RuIII(CN-sap)(CN)3]2– (1) are described. Complex 1 reacts with [MnII(LN5)(Cl)(H2O)]Cl and [MnII(bipy)2(Cl)2] (bipy = bipyridine) to produce the 1D zigzag chain {[RuIII(CN-sap)(CN)](?-CN)2[MnII(LN5)]·3MeOH}n {2; LN5 = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, CN-sapH2 = 2-hydroxy-N-(2-hydroxyphenyl)benzimidoyl cyanide} and the octanuclear compound {[RuIII(CN-sap)(CN)](?-CN)2[MnII(bipy)(MeOH)][RuIII(CN-sap)](?-CN)3[MnII(bipy)2]}2·8MeOH (3), respectively. The MnII centers have a pentagonal-bipyramidal environment in 2 and a distorted octahedral environment in 3. Complex 1 reacts with [NiII(cyclen)(Cl)2] (cyclen = 1,4,7,10-tetraazacyclododecane) in MeOH to produce the molecular square {[RuIII(CN-sap)(CN)](?-CN)2[NiII(cyclen)]}2·8MeOH (4). Compounds 2 and 3 exhibit antiferromagnetic coupling between the RuIII and MnII centers, whereas 4 exhibits ferromagnetic coupling between the RuIII and NiII centers through the cyano bridges. Three new cyano-bridged heterodimetallic compounds have been obtained from the paramagnetic RuIII building block mer-[RuIII(CN-sap)(CN)3]2– (1). Their structures and magnetic properties have been investigated.

Posted on 29 January 2015 | 1:30 pm

Nitric Oxide and Nitroxyl Products from the Reaction of L-Cysteine with trans-[RuNO(NH3)4P(OEt)3](PF6)3

The reaction between the trans-[RuNO(NH3)4P(OEt)3](PF6)3 and L-cysteine (RS–) was studied over a pH range of 2.0–7.4. In this reaction, the concentrations of NO and HNO produced varied as a function of the pH of the solution. The first step of this reaction proceeded quickly [k1 = (3.5?±?0.3)?×?103 M–1 s–1, pH = 3.5, 25 °C] and resulted in the formation of trans-[Ru(NH3)4P(OEt)3N(O)SR]2+, which dissociated to yield trans-[Ru(NH3)4P(OEt)3NO·]2+ and RS·. However, trans-[Ru(NH3)4P(OEt)3N(O)SR]n–1 can react with a second L-cysteine, yielding trans-[Ru(NH3)4P(OEt)3N(O)(SR)2]+ [k2 = (3.6?±?0.1) M–1?s–1, pH = 3.5, 25 °C]. Therefore, the trans-[Ru(NH3)4P(OEt)3NO·]2+ species released NO and the trans-[Ru(NH3)4P(OEt)3N(O)(SR)2]n–2 species released HNO. The concentration of nitric oxide and nitroxyl generated from the reaction between trans-[RuNO(NH3)4P(OEt)3](PF6)3 and cysteine can be modulated by altering the pH. The nucleophilic attack of RS– yielded mostly trans-[Ru(NH3)4P(OEt)3N(O)SR]2+ at pH ? 4.0 and trans-[Ru(NH3)4P(OEt)3N(O)(SR)2]2+ at pH ? 6.0, which decompose into NO and HNO, respectively.

Posted on 29 January 2015 | 1:30 pm

Allylpalladium(II) Histidylidene Complexes and Their Application in Z-Selective Transfer Semihydrogenation of Alkynes

We have studied the use of amino acid histidine as a precursor for N-heterocyclic carbene (NHC) ligands. This natural amino acid possesses an imidazole substituent, which makes it an interesting NHC precursor that contains both an acid and an amino functionality. These functionalities may be used for further tuning of NHC complexes. We have developed routes for the synthesis of symmetric and dissymmetric alkyl, benzyl, and aryl-substituted histidinium salts. Subsequently, the corresponding Ag and Pd histidylidenes were synthesized and the palladium complexes were tested in the Z-selective transfer semihydrogenation of alkynes. Histidylidene palladium complexes that contain additional donor functionalities were found to display good selectivities. The best catalytic results were obtained with a Pd-histidylidene complex that contains two picolyl functional groups. From an amino acid to versatile ligands and catalysts. Synthetic routes to histidinium salts and AgI and PdII histidylidenes were developed. The Pd-histidylidenes were subsequently investigated in the transfer semihydrogenation of alkynes to Z-alkenes

Posted on 29 January 2015 | 1:30 pm

Photoinduced Rearrangement of Aryl-Substituted Acylcyclohexasilanes

In the present study, we examined photochemical transformations of acylcyclohexasilanes (Me3Si)2Si6Me12(Me3Si)COR (compounds 1) with aromatic substituents attached to the carbonyl C atom. When photolyzed at wavelengths above 300 nm in hydrocarbon solvents, 1a–c (1a: R = o-Tol; 1b: R = 2,3-Me2C6H3; 1c: R = 2,4-Me2C6H3) afforded the previously unknown eight-membered heterocyclopolysilanes 3a–c, which feature endocyclic Si=C double bonds with remarkable selectivity. If two ortho-alkyl groups are present at the aromatic ring (compounds 1d–f), the primary products of type 3 (3d: R = Mes; 3e: R = 1,6-Me2C6H3; 3f: R = 2,4,6-iPr3C6H2) are photochemically unstable and undergo intramolecular C–H-bond addition reactions of a ortho-CH3 group to the Si=C double bond, which leads to the formation of spirobenzocyclobutenes. When photolysis was performed in the presence of methanol, the expected 1,2-addition products (compounds 4) of the Si=C double bond were obtained quantitatively in all cases. 4a (R = o-Tol) and 4b (R = Mes) were isolated by crystallization from acetone and fully characterized spectroscopically and by single-crystal X-ray diffraction analysis. Interestingly 4b was obtained as an isomeric mixture arising from syn and anti addition of methanol to the endocyclic Si=C bond, whereas the syn addition was observed exclusively in the case of 4a. Stable cyclopolysilanes with endocyclic Si=C double bonds were synthesized by the photolysis of acylcyclohexasilanes with bulky aromatic substituents at the carbonyl C atom. The substitution pattern of the aromatic ring significantly influences the photolytical stability of the products. Characterization was achieved spectroscopically by X-ray crystallography and by trapping experiments.

Posted on 29 January 2015 | 1:30 pm

A Metalloligand Appended with Thiazole Rings: Heterometallic {Co3+–Zn2+} and {Co3+–Cd2+} Complexes and Their Hetero­geneous Catalytic Applications

This work describes a Co3+-based metalloligand containing appended thiazole rings and its reactions with secondary metal ions to produce heterometallic {Co3+–Zn2+} and {Co3+–Cd2+} complexes. Structural studies show that some of the appended thiazole rings from the metalloligand coordinate to secondary metal ions, whereas the remaining ones act as hydrogen-bond acceptors to metal-bound CH3OH or H2O molecules. These heterometallic complexes function as reusable heterogeneous catalysts for the ring-opening reactions of epoxides as well as cyanation and Knoevenagel condensation reactions of aldehydes. The catalytic results illustrate that the microenvironment remains intact during the catalysis and potentially enhances the substrate interaction with the Lewis acidic secondary metal ions. A Co3+-based metalloligand with appended thiazole rings is used to synthesize heterometallic {Co3+–Zn2+} and {Co3+–Cd2+} complexes. These complexes function as reusable heterogeneous catalysts for ring-opening, cyanation, and Knoevenagel condensation reactions. The results illustrate the importance of the microenvironment of catalytic metal centers to potentially enhance substrate interactions.

Posted on 27 January 2015 | 2:20 pm

Intercalative Ion-Exchange Route to Amino Acid Layered Double Hydroxide Nanohybrids and Their Sorption Properties

A soft chemical route to amino acid layered double hydroxide (LDH) nanohybrids was demonstrated on the basis of an intercalative ion-exchange reaction. Two different amino acids, phenylalanine and glutamic acid, were intercalated and stabilized in the interlayer space of a 2-dimensional double hydroxide lattice by electrostatic interaction. An attempt was also made to understand the effect of the intracrystalline structure of the amino acid in the LDH on the specific surface area, porosity, and gas sorption properties of the hybrid. According to the X-ray diffraction analysis, the basal spacings of LDH intercalated with phenylalanine and LDH intercalated with glutamic acid were expanded to 1.80 and 1.22 nm, respectively, relative to that of the pristine Mg2Al-NO3-LDH (0.88 nm), which indicates that amino acid molecules were successfully intercalated into the LDH. Fourier transform infrared spectra for both samples confirmed that the carboxylic acid group in the amino acid is anionic carboxylate under basic conditions and it eventually interacts with the positively charged LDH surface. From N2 adsorption/desorption analysis, the BET specific surface area of the LDH intercalated with phenylalanine was found to be twice as large as that for the LDH intercalated with glutamic acid. However, the CO2 adsorption capacity of the former was determined to be three times more enhanced than that of the latter, due to an enhanced specific surface area and effective amine sites to form carbamates. The CO2 uptake capacity in the present study is influenced not only by the specific surface area but also by the number of reactive amine sites in the pore, as the amine groups of amino acids interact with adsorbed CO2 molecules to form carbamates by a zwitterionic mechanism even at low temperature.

Posted on 27 January 2015 | 2:20 pm

Lanthanide Complex Hybrid System for Fluorescent Sensing as Thermometer

A mixed lanthanide complex was synthesized hydrothermally with two kinds of organic ligands, adenine and biphenyl-4,4?-dicarboxylic acid, and is formulated as Ad/Tb0.999Eu0.001/BPDC (Ad = adeninate, BPDC = biphenyl-4,4?-dicarboxylate). The photophysical properties, especially the fluorescent sensing properties, have been studied in detail and compared to those of Tb0.999Eu0.001/BPDC, with a single ligand. It can be used as a ratiometric luminescent thermometer on the basis of the energy transfer from Tb3+ to Eu3+, whose color will change from green–yellow to red from 100 K to 300 K. A mixed lanthanide complex was synthesized hydrothermally with two organic ligands, adenine and biphenyl-4,4?-dicarboxylic acid, and is formulated as Ad/Tb0.999Eu0.001/BPDC (Ad: adeninate, BPDC: biphenyl-4,4?-dicarboxylate). It can be used as a ratiometric luminescent thermometer on the basis of the energy transfer from Tb3+ to Eu3+, whose color changes from green–yellow to red from 100 to 300 K.

Posted on 27 January 2015 | 2:20 pm

The First Heterotrinuclear Confacial Trioctahedron NiIITiIVCrIII: Rational Modular Assembly and Cooperative Effects

The heterodinuclear complex [(ioan)NiIITiIV] with a facial O3 donor set of TiIV-coordinated benzyl alcoholates serves as a metallo-ligand for a {CrIIICl3} fragment to yield the heterotrinuclear complex [(ioan)NiIITiIVCrIIICl3]. Comparisons of their molecular structures and electrochemical properties exhibit strong cooperative effects between the metal ions. The ligand H6ioan allows the synthesis of the first confacial trioctahedron [(ioan)NiTiCrCl3] with three different metal ions.

Posted on 27 January 2015 | 2:20 pm

5-Ferrocenyl-1H-tetrazole-Derived Transition-Metal Complexes: Synthesis, Crystal Structures and Catalytic Effects on the Thermal Decomposition of the Main Components of Solid Propellants

With the aim of developing low-migratory burning-rate (BR) catalysts for solid propellants, a series of transition-metal complexes of 5-ferrocenyl-1H-tetrazole (HFcTz), [Cu2(bpy)2(FcTz)4]·2C2H5OH (1), [Pb(phen)2(H2O)3](FcTz)2·H2O (3), [Cu(phen)3](FcTz)2·8H2O (4), [Mn(phen)2(H2O)2](FcTz)2 (5), [Mn(bpy)(H2O)4](FcTz)2 (6), [Ni(phen)3](FcTz)2·9H2O (7), and [Co(phen)3](FcTz)2·9H2O (8) (bpy = 2,2?-bipyridine; phen = 1,10-phenanthroline), were synthesized and structurally characterized. Only a limited number of single crystals of [Pb2(phen)4(CO3)](FcTz)2·phen·9H2O (2) were formed so only its crystal structure was analyzed. The complexes show high thermal stability. Cyclic voltammetry investigations suggested that 1 and 3–7 exhibit quasireversible redox systems. Their catalytic effects on the thermal degradation of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) were evaluated by differential scanning calorimetry (DSC) and thermogravimetric (TG) methods. The optimum content of the new compounds in AP, RDX, and HMX was established to be 5, 5, and 2 wt.-%, respectively. They exhibit high catalytic activities in the thermal decomposition of AP and RDX. Among them, 6 was found to be the best ferrocene-based BR catalyst. Eight 5-ferrocenyl-1H-tetrazole-derived transition-metal complexes have been synthesized and characterized by single-crystal X-ray diffraction. The new compounds exhibit high thermal stability and large catalytic effects on the thermal degradation of ammonium perchlorate and 1,3,5-trinitro-1,3,5-triazacyclohexane.

Posted on 26 January 2015 | 10:20 am

Tracing the Iron Nitrosyl Complex [Fe(2,2?-bipyridine)(CN)3(NO)]–

The previously reported complex [Ph4P][Fe(bpy)(CN)3(NO)] (bpy = 2,2?-bipyridine) was synthesised and characterised in detail using UV/Vis absorption and IR spectroscopy, cyclic voltammetry, and single-crystal XRD. Detailed spectroelectrochemical (UV/Vis, IR and EPR) insight adds perfectly to the previous electrochemical characterisation of this complex. The description of this {Fe(NO)}7 complex as a low-spin FeII–NO· system based on the spectroscopic results is supported by DFT calculations. Reversible oxidation leads to the corresponding {Fe(NO)}6 (FeII–NO+) complex, whereas the reduction to the formal {Fe(NO)}8 species [presumably (FeII–NO–)] occurs irreversibly. When trying to synthesise further derivatives that contain other ?-diimine ligands, only for the 1,10-phenanthroline (phen) derivative were some results obtained. For other ligands the obtained materials were too reactive. The reasons for such behaviour are also discussed. The previously reported complex [Ph4P][Fe(bpy)(CN)3(NO)] (bpy = 2,2?-bipyridine) was synthesised and a detailed structural (single-crystal XRD), (spectro)electrochemical and spectroscopic insight is provided that adds perfectly to the previous electrochemical characterisation.

Posted on 23 January 2015 | 2:10 pm

Crystalline Non-Equilibrium Phase of a Cobalt(II) Complex with Tridentate Ligands

In six-coordinate complexes, flexible tridentate ligands enable mer, cis-fac, and trans-fac stereoisomers. With labile metal ions of the first transition metal series, typically only the final thermodynamic product is available because of the rapid isomerization processes. Here we report on the structural characterization of a so far elusive kinetic intermediate of [Co(ddpd)2](BF4)2 (1; ddpd = N,N?-dimethyl-N,N?-dipyridine-2-yl-pyridine-2,6-diamine). Microcrystals of the cis-fac isomer of 1 were obtained by rapid precipitation. The solid-state structure of cis-fac-1 was determined from electron diffraction data. Rapid precipitation yields microcrystals of the so far elusive kinetic intermediate of [Co(ddpd)2](BF4)2 (ddpd = N,N?-dimethyl-N,N?-dipyridine-2-yl-pyridine-2,6-diamine). Its solid-state structure has been determined from electron diffraction data.

Posted on 23 January 2015 | 2:10 pm

Mechanistic Insights into Phenol Oxidation by a Copper(II) Complex of a Pyridine- and Amide-Containing Copolymer in an Aqueous Medium (Eur. J. Inorg. Chem. 3/2015)

The cover picture shows the two distinct pathways for phenol hydroxylation and oxidation by the copper complex of a copolymer in an aqueous medium, that is, a dinuclear and a mononuclear mechanism with H2O2 and air, respectively, as the oxidation agents. Despite the random sequence and heterogeneity of this copper–copolymer complex, the rates of catalysis achieved are comparable to or better than those of many metal complexes with well-defined structures. This copper–copolymer complex may serve as a blueprint for further design of metallopolymers with various chemical and physical properties by modification of the metal-binding ligands and the side chains. The water splash (1/125 s) and the floating leaves in the background hint the green chemistry nature of the research. Details are discussed in the article by V. Lykourinou and L.-J. Ming on p. 375 ff. For more on the story behind the cover research, see the Cover Profile.

Posted on 22 January 2015 | 7:44 pm

Mechanistic Insights into Phenol Oxidation by a Copper(II) Complex of a Pyridine- and Amide-Containing Copolymer in an Aqueous Medium

Invited for the cover of this issue is the group of Li-June Ming at the University of South Florida, USA. The cover image shows the pathways for phenol oxidation by copper(II) centers of a copolymer scaffold in an aqueous environment, representing a green method for chemical processes and environmental remediation. The easy preparation of the metallopolymers and their potential in various metal-mediated catalysis reactions will allow us to explore broad applications...Read more about the story behind the cover in the Cover Profile and about the research itself on p. 375 ff.

Posted on 22 January 2015 | 7:44 pm

Graphical Abstract: Eur. J. Inorg. Chem. 3/2015

Posted on 22 January 2015 | 7:44 pm

Masthead: Eur. J. Inorg. Chem. 3/2015

Posted on 22 January 2015 | 7:44 pm

Metal–Organic Frameworks Based on Alkaline Earth Metals – Hydrothermal Synthesis, X-ray Structures, Gas Adsorption, and Heterogeneously Catalyzed Hydrogenation Reactions

New carboxylate systems with alkaline earth metals, namely, [Ca2Na2(L)2(H2O)6]n·nH2O (1, H3L = chelidamic acid) and [Sr3(L)2(H2O)9]n·2nH2O (2), have been prepared by hydrothermal reactions and characterized. The compounds featured different three-dimensional (3D) structural motifs and new topologies. The amount of void space for the dehydrated materials of 1 and 2 was calculated to be ca. 19 and 35?%, respectively. The dehydrated materials are thermally stable to more than 450 °C. The dehydrated species of 1 and 2 displayed excellent N2, H2, and CO2 sorption capacity at 1 atm pressure. Furthermore, both compounds efficiently catalyze the hydrogenation of alkenes under mild heterogeneous conditions (60 °C, 1 atm H2). The porous catalysts demonstrate size selectivity towards substrates owing to presence of active sites inside the pores of the MOF. Compounds generated by the thermal dehydration of Ca- and Sr-based metal–organic frameworks (MOFs) possess pores with open unsaturated metal sites and exhibit excellent adsorption capacity for N2, H2, and CO2 at low pressure. The calcined MOFs catalyze the hydrogenation of olefins under mild heterogeneous conditions (60 °C, 1 atm H2).

Posted on 22 January 2015 | 9:30 am

Three Scandium Compounds with Unsaturated Coordinative Metal Sites – Structures and Catalysis

Two scandium coordination polymers, a 2D supermolecule structure {[Sc(OH)(L1)2(H2O)]}n (1) (HL1 = isonicotinic acid), a 1D infinite chain structure {[Sc3(L2)4(H2O)4]·NO3·H2O}n (2) (H2L2 = 4,5-imidazole dicarboxylic acid), as well as a scandium complex {[Sc2(OH)2(L3)2(H2O)4]}n (3) (H2L3 = 1,2,3-triazole-4,5-dicarboxylic acid), were synthesized and characterized by X-ray crystallography. Compounds 1–3 are active heterogeneous catalysts for high-yield cyanosilylation of aromatic aldehydes in acetonitrile, particularly for p-nitrobenzaldehyde. Moreover, these three catalysts can be reused three times without significant loss in activity or mass. Three scandium compounds have been prepared under solvothermal conditions. These new materials are stable in CH3CN and show good Lewis acid catalytic activity for cyanosilylation of aromatic aldehydes by virtue of their coordinative unsaturated metal sites. Over successive cycles, a small decrease in activity was observed for two of the catalysts.

Posted on 22 January 2015 | 9:20 am

Crystallographic and Spectroscopic Investigations on Nine Metal–Rare-Earth Silicates with the Apatite Structure Type

Nine silicates with the apatite structure type (space group P63/m) containing both rare-earth elements (REEs: Pr, Nd, Sm, Tb, Ho and Er) and various metals (K, Sr, Ba and Cd) were synthesised by high-temperature flux-growth techniques and characterised by single-crystal X-ray diffraction, scanning electron microscopy, Raman spectroscopy and laser-induced photoluminescence spectroscopy. In all of the compounds, the 6h Wyckoff position is predominantly or solely occupied by REE3+ cations, whereas the cations shows a mixed occupancy at the larger, nine-coordinate 4f site with 55–75?% of REE3+ cations and 45–25?% of other metal cations. The O4 (“free” oxygen) site is fully occupied by O2– anions, except for a Ba–Pr member with full occupancy by F– anions. The refined formulas are Cd2Er8(SiO4)6O2, Cd2Tb8(SiO4)6O2, KHo9(SiO4)6O2, KTb9(SiO4)6O2, KSm9(SiO4)6O2, Sr2Nd8(SiO4)6O2, Ba2Nd8(SiO4)6O2, Ba2Sm8(SiO4)6O2 and Ba4Pr6(SiO4)6F2. Changes in the metaprism twist angle (?) and correlations between the unit-cell parameters, average cationic radii (of M+/M2+–REE3+ pairs) and the chemistry of both the synthesised M+/M2+–REE3+ silicate apatites and those reported previously are evaluated. Photoluminescence measurements of undoped samples yielded emission bands in the visible region from green to red; therefore, these compounds are potential candidates for luminescent materials. Nine metal–rare-earth silicates with the apatite structure type were synthesised by a high-temperature flux-growth technique. Their metaprism twist angle depends on the anions present in the crystal structure, and their photoluminescence properties could be useful for luminescent devices.

Posted on 22 January 2015 | 9:20 am

A Series of Noncentrosymmetric Antimony Sulfides Ln8Sb2S15 (Ln = La, Pr, Nd) – Syntheses, Crystal and Electronic Structures, and NLO Properties

A series of noncentrosymmetric sulfides Ln8Sb2S15 (Ln = La, Pr, Nd) were prepared from stoichiometric mixtures of the elements at 1223 K in an evacuated silica tube. The compounds Ln8Sb2S15 with Ln = La and Nd are isostructural to Pr8Sb2S15 and crystallize in the tetragonal noncentrosymmetric space group I41cd. Their structure contains discrete [SbS3]3– trigonal pyramids separated by Ln3+ cations and S2– anions. La8Sb2S15 shows second harmonic generation with intensities 1.2 times that of the commercially used IR NLO (nonlinear optics) material AgGaS2 (at 2.05 ?m laser). It exhibits excellent thermal stability up to 663 °C. Studies with UV/Vis–NIR diffuse reflectance spectroscopy show that La8Sb2S15 has an optical gap of around 2.3 eV, and a DFT study indicates a direct band gap with an electronic transfer excitation of S 3p electrons to a La 5d orbital. A series of noncentrosymmetric antimony sulfides Ln8Sb2S15 (Ln = La, Pr, Nd) were prepared. Their structures contain discrete [SbS3]3– trigonal pyramids separated by the Ln3+ cations and S2– anions. The compound La8Sb2S15 shows second harmonic generation with intensities 1.2 times that of the commercially used IR NLO material AgGaS2.

Posted on 22 January 2015 | 9:20 am

Facile Preparation of Mn+-Doped (M = Cu, Co, Ni, Mn) Hierarchically Mesoporous CeO2 Nanoparticles with Enhanced Catalytic Activity for CO Oxidation

A series of transition-metal-doped (Cu, Co, Ni, Mn) hierarchically mesoporous CeO2 nanoparticles have been fabricated through a simple solvothermal strategy. The effect of these doping metals on the morphology and the phase transformation of the Ce(HCOO)3 precursor was investigated. The specific order in which the doping metal cations (except Cu2+) are added during the synthesis process has a remarkable influence on the precursor morphology. By introducing these different metal cations, the doping composition can be adjusted freely. The XRD, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results show the high homogeneity of the doped ceria and demonstrate that the transition metal cations have been incorporated into the CeO2 lattice. All of the doped ceria nanoparticles, especially the Cu2+-doped ceria product, exhibit improved reduction behavior and enhanced CO conversion performance. A series of transition-metal-doped (Cu, Co, Ni, Mn) hierarchically mesoporous CeO2 nanoparticles assembled from hollow nanocones were prepared through a simple solvothermal strategy. The doped ceria nanoparticles exhibit improved reduction behavior and enhanced catalytic activity for CO oxidation.

Posted on 22 January 2015 | 9:20 am

The Orthoperiodates of Calcium, Strontium, and Barium

Orthoperiodates of calcium, strontium, and barium were prepared by solid-state reactions of metal iodides or metal iodates with oxygen in air. M(IO3)2 (M = Ca) or MI2 (M = Sr, Ba) were heated in an open corundum crucible to yield M5(IO6)2 as a product with beige to light brown body color. Reactions were investigated by thermal analyses, using differential thermal analysis (DTA) and thermogravimetric analysis (TGA). Two distinct crystal structures were assigned for M5(IO6)2 with the space group R$\bar {3}$c for M = Ca, Sr (isotypic with Ca, Sr perrhenates) and Pnma for M = Ba based on recorded powder X-ray diffraction data. Luminescence properties of europium-doped samples are reported. Orthoperiodates of calcium, strontium, and barium were prepared by solid-state reactions of metal iodides or metal iodates with oxygen in air. The reactions were investigated by using differential thermal analysis and thermogravimetric analysis. Luminescence properties of europium-doped samples are reported.

Posted on 22 January 2015 | 9:20 am

Discrete FeII Spin-Crossover Complexes of 2,2?-Dipyridylamino-Substituted s-Triazine Ligands with Phenoxo, Cyanophenoxo and Dibenzylamino Functionalities

Four 2,2?-dipyridylamino-s-triazine-substituted ligands, each of which incorporate different aromatic substituents (phenoxo, 4-CN-phenoxo and benzylamino) with different degrees of bulk and flexibility, have been formed and incorporated into a number of mononuclear FeII complexes of type trans-[FeII(L)2(NCX)2]·solvent (in which X = S, Se and BH3). These ligands were designed to promote ?–? stacking between complexes. The complexes reported have been comprehensively characterised using single-crystal diffraction techniques in combination with magnetic susceptibility measurements. Light-induced excited spin-state trapping (LIESST) measurements have been performed on selected complexes. Light irradiation has shown the occurrence of a reversible photoswitching process at low temperature. New mononuclear spin-crossover compounds of type trans-[FeII(NCX)2(L)2]·solvent have been synthesised and structurally characterised. The L ligands are chelated to Fe by dipyridylamine groups and have aromatic substituents on the central triazine ring that influence cooperativity effects monitored by magnetic and light-induced excited-state spin trapping (LIESST) measurements.

Posted on 20 January 2015 | 10:30 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

Reactivity of Dinitrogen Bound to Mid- and Late-Transition-Metal Centers

This review presents a comprehensive overview of the reactions of N2 within the coordination sphere of transition metals of groups 6 to 9. Many of these metals mediate the reaction of N2 with protons under reductive conditions, which can lead to the (catalytic) formation of ammonia or hydrazine, and the mechanisms of these reactions somewhat resemble the mode of action of nitrogenase enzymes. Alternatively, coordinated N2 can react with carbon and silicon electrophiles and radicals to allow, for example, the catalytic formation of silylamines. Another approach in N2 activation involves the homolytic splitting of dinitrogen to form intermediate nitrides in analogy to the Haber–Bosch process. Thus formed nitrides can undergo follow-up reactions with protons or carbon electrophiles. Molybdenum, tungsten, and iron reveal the richest chemistry of coordinated N2; however, chromium, manganese, rhenium, osmium, and cobalt systems provide alternative pathways in the making and breaking of bonds on the dinitrogen molecule. Mid- and late-transition metals are excellent platforms for enabling the reactivity of dinitrogen. This microreview gives an overview of the many reactions in which N2 is cleaved or forms new bonds with electrophiles or radicals. These reactions occur under ambient conditions, and some of them, such as the formation of ammonia or silylamines, are even catalytic.

Posted on 20 January 2015 | 10:30 am

Formation of Different Isomers of Phosphine–Imidazolyl and –Pyridyl Ruthenium(II) Complexes Affecting the Catalyst Activity in the Acceptorless Dehydrogenation of Alcohols

The synthesis, reactivity, and catalytic activity of RuII complexes with different pyridine- and imidazole-based P,N ligands are reported. The investigations reveal a strong influence of the N-heterocycle and the steric demand of the phosphine groups on the stability of different isomers of [L2RuX2] (L = P,N ligand; X = Cl, H). The imidazole-based complex 5 with dicyclohexylphosphine groups was found to be the most active precatalyst for the acceptorless dehydrogenation of primary alcohols, whereas different phosphine groups at the imidazole ligand as well as pyridine-based ligands caused a drop in catalytic activity. In the presence of a primary amine, imines are preferentially formed under these conditions. In summary, the investigations show that comparably small changes in the ligand moiety have a strong effect on the relative stability of stereoisomers for both hydride and chloride complexes, whereas isomerization of the kinetic reaction products was observed in some cases. The described changes in the ligand moiety most probably have a strong impact on the relative stabilities of isomeric intermediates as well and thus affect the catalytic activity of these complexes. Different ruthenium dichloride complexes with P,N ligands have been synthesized and compared in their activity in the acceptorless dehydrogenation of primary alcohols, thereby demonstrating that small changes in the ligand moiety have a strong impact on the relative stability of isomeric dihydride and dichloride complexes and thus on the catalytic activity.

Posted on 19 January 2015 | 2:10 pm

Homoleptic and Heteroleptic Bismuth(III) Thiazole–Thiolates and the Influence of Ring Substitution on Their Antibacterial and Antileishmanial Activity

Two new homo- and heteroleptic bismuth thiazole-thiolato complexes derived from 4-phenylthiazole-2-thiol MBT(H) have been synthesised and structurally characterised, [BiPh(MBT)2]2 and [Bi(MBT)3]2. Syntheses were achieved using BiPh3 or Bi(OtBu)3 in protolysis reactions with MBT(H), or by salt metathesis with BiCl3 or BiPhCl2 and the sodium thiolate, [NaMBT]. The complexes were obtained under both standard solvent-free and solvent-mediated conditions, and by microwave irradiation. The solid-state structures of [BiPh(MBT)2]2 and [Bi(MBT)3]2, were determined using single-crystal X-ray diffraction, showing them to be dimeric. The bactericidal properties of the complexes against Mycobacterium smegmatis, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, vancomycin-resistant Enterococcus (VRE) and Escherichia coli revealed [BiPh(MBT)2]2 to be the most effective against all the bacteria with MIC values of 0.6 ?g/mL (0.25 ?M) against S. aureus and 0.9 ?g/mL (0.27 ?M) against E. faecalis. [Bi(MBT)3]2 was less active overall. However, comparisons with the analogous complex [Bi(4-BrMTD)3], revealed a significant hundred-fold enhanced activity against S. aureus, MRSA, VRE, and E. faecalis. Both complexes showed little or no toxicity towards mammalian COS-7 cells at 20 ?g/mL. [BiPh(MBT)2]2 also was found to display good antileishmanial activity with an IC50 value of 0.11 ?g/mL (0.17 ?M), at which concentration the complex was non-toxic to human fibroblast cells. Thiazole-based bismuth(III) complexes, [BiPh(MBT)2]2 and [Bi(MBT)3]2, derived from 4-phenylthiazole-2-thiol, MBT(H), have been synthesised and structurally characterised; X-ray diffraction studies played a central role in structure elucidation efforts. [BiPh(MBT)2]2 is strongly active against common and multi-resistant bacteria, and against the Leishmania parasite.

Posted on 19 January 2015 | 2:10 pm

UPTe, ThPTe and U2PTe2O: Actinide Pnictide Chalcogenides with Diphosphide Anions

Crystal structure determination of UPTe revealed a UGeTe derivative structure with a pseudo-tetragonal unit cell with lattice parameters a = 410.1(1) pm and c = 1697.1(1) pm at 120(2) K. ThPTe can be regarded as isotypic according to powder X-ray diffraction data, its pseudo-tetragonal lattice parameters are a = 425.05(1) pm and c = 1726.8(1) pm at 296(1) K. Real-space topological analysis of the chemical bonding and Raman data reveal the presence of P2 units. U2PTe2O can be considered as a partially oxidised phosphide telluride with a pseudo-tetragonal unit cell, a = 403.7(1) pm, and c = 3206.8(10) pm at 120(2) K. Single-crystal X-ray diffraction data of UPTe and U2PTe2O indicate an ordered orientation of the P2 dumbbells leading to a monoclinic distortion, which implies a symmetry decrease to space group I11m. Single crystal structure investigations, Raman data and real-space bonding analysis unveil the presence of diphosphide anions in UPTe. For hitherto unknown ThPTe, X-ray powder data indicate an analogous structural pattern. The new compound U2PTe2O, a partially oxidised variant of UPTe, also contains layers of P2 anions in a parallel arrangement.

Posted on 19 January 2015 | 12:40 pm

3D Microporous Lanthanide–Organic Frameworks Constructed from Left- and Right-Handed Helical Chains: Synthesis, Crystal Structure, and Tunable Photo­luminescence

New lanthanide–organic frameworks, [Ln2(2,6-NDS)3(IP)(H2O)4]·H2O {Ln = Sm (1), Eu (2), Tb (3); 2,6-NDS = 2,6-Anaphthalenedisulfonate, IP = 1H-imidazo[4,5-f][1,10]-phenanthroline}, were synthesized and characterized. These complexes are isostructural and have three-dimensional structures (3D) composed of a pair of entanglement double helixes. The structure is an open framework with rhombic channels filled with uncoordinated water molecules. The photoluminescence properties of the SmIII complex (1) and EuIII/TbIII-doped complex were explored by adjusting the excitation wavelengths. Interestingly, SmIII complex 1 generated a white-light emission, whereas the EuIII/TbIII-doped complex (Tb0.95Eu0.05) allowed the realization of white-light emission under broad UV wavelengths. An energy transfer for TbIII 5D4EuIII 5D0 was observed. Lanthanide frameworks were assembled from 2,6-naphthalenedisulfonate and 1H-imidazo[4,5-f][1,10]-phenanthroline. They have 3D microporous structures constructed from left- and right-handed helical chains. The SmIII complex and the EuIII/TbIII-doped complex allowed the realization of luminescence tuning and white-light emission.

Posted on 19 January 2015 | 12:40 pm

Synthesis and Structure–Activity Relationships of Gadolinium Complexes of DO3A–Benzothiazole Conjugates as Potential Theranostic Agents

The synthesis of two bifunctional chelates, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) conjugates of benzothiazoles (H3L3a and H3L3b), and the corresponding gadolinium complexes (GdL3a and GdL3b) was achieved. The intracellular and tumor-specific nature of GdL3a and GdL3b were confirmed by magnetic resonance images of the cytosols and nuclei of various cell lines. The two complexes displayed antitumor activities with varying degrees of growth-inhibition and total-growth-inhibition values depending on the types of tumor cells. They caused morphological changes in tumor cell lines at much lower concentrations of gadolinium ([Gd] ? 50 ?M) than their predecessors, DO3A–(p-aniline benzothiazole) conjugates (H3L1), and its GdIII complex (GdL1) required concentrations that were almost four times as high ([Gd] ? 200 ?M). The synthesis of DO3A derivatives of benzothiazole and their Gd complexes for use as single-molecule theranostic agents is reported. The complexes are tumor specific and are also intracellular, which enhances magnetic resonance images of cytosols and nuclei of various tumor cells. GdL3 reveals antiproliferative activities, as demonstrated by growth-inhibition and total-growth-inhibition values.

Posted on 15 January 2015 | 1:22 pm

Dicationic ?-Diborolyl Arene Triple-Decker Complexes [CpCo(?-1,3-C3B2Me5)M(arene)]2+ (M = Rh, Ir; Cp = Cyclopentadienyl): Synthesis, Structures, Electrochemistry and Bonding

The reaction of the bromide complexes [CpCo(?-1,3-C3B2Me5)MBr2]2 [M = Rh (1), Ir (2); Cp = cyclopentadienyl] with AgBF4 in acetonitrile affords the tris(acetonitrile) ?-diborolyl triple-decker complexes [CpCo(?-1,3-C3B2Me5)M(MeCN)3]2+ [Rh (3), Ir (4)]. The labile nitromethane solvates [CpCo(?-1,3-C3B2Me5)M(MeNO2)3]2+, generated in a similar way, react with benzene and its methylated derivatives to give the arene triple-decker complexes [CpCo(?-1,3-C3B2Me5)M(arene)]2+ [M = Rh (5), Ir (6); arene = C6H6 (a), 1,2,4,5-Me4C6H2 (b), C6Me6 (c)]. The structures of 5b(BF4)2, 5c(BF4)2, 6b(BF4)2 and 6c(BF4)2 were determined by X-ray diffraction. The electron-transfer ability of the arene complexes was ascertained by electrochemical techniques. In general, they are able to undergo two separate one-electron reductions reversibly. DFT calculations revealed structural changes caused by redox processes and satisfactorily predicted the redox potentials. The second reduction is accompanied by a ?6???4 hapticity change of the arene ligand. Energy decomposition analysis revealed that the Rh–benzene bond in cation 5a is weaker than in cyclopentadienyl analogues [(C5R5)Rh(C6H6)]2+; however, 5a proved to be the least reactive in benzene replacement with acetonitrile and mesitylene. The labile nitromethane solvates [CpCo(?-1,3-C3B2Me5)M(MeNO2)3]2+ {generated from the bromide complexes [CpCo(?-1,3-C3B2Me5)MBr2]2 (M = Rh, Ir; Cp = cyclopentadienyl) and AgBF4 in MeNO2} react with arenes to give triple-decker complexes [CpCo(?-1,3-C3B2Me5)M(arene)]2+. X-ray diffraction, electrochemical techniques and DFT calculations were used for the characterization of the complexes obtained.

Posted on 15 January 2015 | 1:22 pm

The Unexpected Isolation of Bismuth Tris(carboxylate) Hydrates: Syntheses and Structures of [Bi(Hsal)3(H2O)] and [Bi(Hanth)3(H2O)] (H2sal = 2-OH-C6H4CO2H, Hanth = 2-NH2-C6H4CO2H)

A complex of the composition [Bi(2-OH-C6H4CO2)3(H2O)] (1) was isolated from the 1:3 reaction of BiPh3 with H2sal (H2sal = salicylic acid = 2-OH-C6H4CO2H) in wet xylene, and the analogous anthranilate compound [Bi(2-NH2-C6H4CO2)3(H2O)] (2) was obtained from the 1:3 reaction of Bi(OtBu)3 with Hanth (Hanth = anthranilic acid = 2-NH2-C6H4CO2H) in tetrahydrofuran. Compounds 1 and 2 were fully characterized spectroscopically and by single-crystal X-ray diffraction. Compounds 1 and 2 crystallize in the triclinic space group and display the ?2-(O,O?) binding mode for the oxygen atoms of the carboxylate ligands. There are two independent molecules in the asymmetric units of 1 and 2 that are connected by a weak bridging interaction of the OH or NH2 group to an adjacent molecule. Both bismuth atoms are bound to a H2O molecule, but the distances are highly asymmetric, long Bi···O lengths ranging from 2.74 to 2.89 Å. Treatment of BiPh3 with salicylic acid in xylene in the presence of air leads to the unexpected isolation of the tris(salicylato)bismuth(III) hydrate.

Posted on 15 January 2015 | 1:22 pm

Transition Metal Complexes with 1-Adamantoyl Hydrazones – Cytotoxic Copper(II) Complexes of Tri- and Tetradentate Pyridine Chelators Containing an Adamantane Ring System

Five pentacoordinate copper(II) complexes with 2-acetylpyridine or di(2-pyridyl) ketone 1-adamantoyl hydrazone ligands (Adpy and Addpy, respectively) of the formulae [CuCl2(Adpy)] (1), [Cu2(?-Cl)2(Adpy-H)2] (2), [Cu(NCS)2(Adpy)] (3), [Cu2(?-Cl)2(Addpy-H)2] (4), and [Cu2(NCS)2(?-Addpy-H)2] (5) were synthesized and characterized by spectral, electrochemical, and X-ray structural analysis. Flow cytometry and morphological analysis confirmed that the copper(II) complexes 2 and 5 induced accumulation of a sub-G1 phase population, and fluorescence microscopy indicated the presence of large cells in apoptosis. The interaction of the copper(II) complexes with calf thymus DNA (CT-DNA) was monitored by changes in their UV/Vis spectra. The observed intrinsic binding constants for 2 and 5 (Kb = 1.77?×?106 and 3.58?×?106 M–1, respectively) together with ethidium displacement fluorescence experiments indicate intercalative binding. Complexes 2 and 5 showed nuclease activity against pUC19 plasmid DNA. Five CuII complexes with 2-acetylpyridine or di(2-pyridyl) ketone 1-adamantoyl hydrazones have been prepared and physicochemically characterized. All of the tested complexes exhibit strong cytotoxic activity and induce apoptosis as the primary method of cell death. An intercalative mode of interaction with DNA was determined, and pronounced double-strand cleavage of supercoiled DNA was observed.

Posted on 15 January 2015 | 1:22 pm

Controlled Synthesis of Monodispersed Sub-50 nm Nanoporous In2O3 Spheres and Their Photoelectrochemical Performance

Uniform nanoporous In2O3 nanospheres with high surface areas were synthesized through a simple solvothermal route with ethylenediamine (en) as the solvent. The prepared In2O3 nanospheres with diameters about 50 nm are composed of many nanoparticles with average sizes of ca. 5 nm. The unique nanospheres inherit both the large surface areas of the nanoparticles and the high crystallinity of bulky materials. The introduction of water or some other solvents into the reaction solution results in the formation of InOOH and In(OH)3 particles indicating that en is indispensable for synthesis of In2O3 with a nanoporous nanosphere structure. UV/Vis spectroscopy reveals that the band-gap of synthesized In2O3 nanospheres is about 2.95 eV, mostly close to that of the single-crystalline bcc-In2O3. The PL spectrum of the In2O3 nanospheres shows two emission peaks located at 470 nm and 483 nm. The photocurrent of the prepared In2O3 electrodes by electrophoretic deposition strongly depends on the calcination temperature. The highest photocurrent density up to 1.9 mA?cm–2 at 0.65 V (vs. Ag/AgCl) in 0.1 M Na2SO4 aqueous solution was recorded in the sample annealed at 550 °C. The high photocatalytic activity of the In2O3 nanospheres can be attributed to the high surface area, and the large number of nanopores in the In2O3 nanospheres. Uniform nanoporous In2O3 nanospheres about 50 nm in diameter with high surface areas were synthesized through a simple one-step solvothermal route with ethylenediamine as the solvent. Their photoelectrochemical properties were evaluated after treatment at different calcination temperatures.

Posted on 15 January 2015 | 1:22 pm

Rhenium(I) Complexes with Alkynylphosphane Ligands: Structural, Photophysical, and Theoretical Studies

A family of mono- and bidentate alkynylphosphanes has been used for the preparation of the rhenium(I) phenanthroline complexes [Re(phen)(CO)2(L)2]+ (L = monophosphane), [{Re(phen)(CO)3}2(L)]2+ (L = diphosphane), and [{Re(phen)(CO)2}2(L)2]2+ (L = diphosphane). The dicarbonyl compounds display intense luminescence at 298 K both in solution and in the solid state (?em ? 44?%). The tricarbonyl complexes demonstrate a strong dependence of the emission efficiency on the ancillary ligand L through a pronounced ?–?* contribution of the diphosphane to the electronic transitions, as confirmed by TDDFT studies. In the solid state, the complexes [Re(phen)(CO)2(L)2]+ display significant luminescence rigidochromism that is influenced by the structure of the phosphane substituents. The latter provide a means to fine-tune the photophysical properties of this class of luminophores through variation of the stereochemical characteristics of the ligands that are not directly involved in the electronic transitions. A family of mono- and bidentate alkynylphosphane-rhenium(I) phenanthroline complexes display intense photoluminescence at room temperature both in solution and in the solid state, with the quantum yields reaching 44?%. Modulation of the luminescence characteristics in the solid state has been achieved through variation of the rigidity of the environment.

Posted on 14 January 2015 | 11:10 am

Photoluminescent One-Dimensional Coordination Polymers from Suitable Pyridine Antenna and LnCl3 for Visible and Near-IR Emission

The series of one-dimensional coordination polymers ?1[LnCl3(bipy)(py)2]·py [bipy = 4,4?-bipyridine, py = pyridine; Ln = Gd, Tb, Dy, Ho, Er, Yb] as well as ?1[Lu2Cl5(bipy)2(py)4]?1[LuCl4(bipy)] were synthesized by the reactions of anhydrous LnCl3 with bipy and py. The formation of extended zigzag chains and saltlike band structures with cationic and anionic strands is observed. Pyridine and 4,4?-bipyridine ligands serve as suitable antennas for lanthanide-based luminescence in the visible and near-infrared range through effective sensitization by the ligands followed by emission through the emissive intra-4f transitions of the Ln3+ (Tb3+, Dy3+, Er3+, Yb3+) ions. For ?1[GdCl3(bipy)(py)2]·py, phosphorescence of the coordinated 4,4?-bipyridine ligand with excitation-dependent chromaticity leads to ligand-based emission in the visible range. These processes cannot be observed for the free ligand. The coordination polymers also extend the range of photoluminescence properties of related complexes and metal–organic frameworks (MOFs) and show high efficiency with a quantum yield of 86?% for the Tb3+ compound. The one-dimensional coordination polymers ?1[LnCl3(bipy)(py)2]·py [bipy = 4,4?-bipyridine, py = pyridine; Ln = Gd, Tb, Dy, Ho, Er, Yb] exhibit photoluminescence properties in the visible and infrared region with a tunable energy gap between excitation and emission from UV to near-IR (NIR). The pyridyl ligands act as sensitizers, and the Ln3+-centred emission has quantum yields of up to 86?%.

Posted on 14 January 2015 | 11:10 am

Pyrididine–Carboxylate Ligands as Double-Bridge Spacers in CuI Metallacycles

The addition of pyridine-3-carboxylic acid (3-PyCOOH), (E)-3-(pyridin-3-yl)acrylic acid (3-PyCH=CHCOOH), or 3-(pyridin-4-yl)benzoic acid (3-PyPhCOOH) to the Lewis acidic [Cu(dppf)(NCMe)2][BF4]·2MeCN·2H2O [1·2MeCN·2H2O, dppf = 1,1?-bis(diphenylphosphanyl)ferrocene] in the presence of NEt3 afforded the complexes [Cu2(dppf)2(3-PyCOO)2]·3CHCl3 (2·3CHCl3), [Cu2(dppf)2(3-PyCH=CHCOO)2]·CH2Cl2·C6H14 (3·CH2Cl2·C6H14), and [Cu2(dppf)2(3-PyPhCOO)2]·CH2Cl2 (4·CH2Cl2) with a common metallomacrocycle core and doubly bridging pyridine–carboxylate ligands as spacers. These dinuclear complexes have been structurally characterized by single-crystal X-ray crystallography, and their emission activities have been studied. Pyridine–carboxylate-bridged dinuclear CuI complexes capped by 1,1?-bis(diphenylphosphanyl)ferrocene (dppf) exhibit macrocycles with diagonal distances of 6.586, 9.159, and 10.006 Å. Such cavity sizes are formed by the introduction of CH=CH or phenyl units into the original pyridine-3-carboxylic acid (3-PyCOOH) spacer.

Posted on 14 January 2015 | 11:10 am

Synthesis and Characterization of Bio-Inspired Diiron Complexes and Their Catalytic Activity for Direct Hydroxylation of Aromatic Compounds

Three [FeFe]-hydrogenase model complexes [(?-dmedt){Fe(CO)3}2] [1; dmedt = SCH(CH3)CH(CH3)S], [(?-dmedt){Fe(CO)3}{Fe (CO)2PPh3}] (1-PPh3), and [(?-dmest){Fe(CO)3}2] [1-O; dmest = SCH(CH3)CH(CH3)S(O)], 1-O were synthesized and characterized. These model complexes, which are generally used as the functional biomimics of the hydrogen-producing dinuclear active site in [FeFe]-hydrogenase, were used as efficient catalysts for the selective hydroxylation of aromatic compounds to phenols under mild conditions. Because both the dithiolato-sulfur site and the Fe–Fe bond in the model complexes were possible active oxidation sites, DFT calculations were used to investigate the oxygenated products, that is, the S-oxygenated products or the Fe-oxygenated forms of the model complexes, which may be involved in the catalytic cycle. The experimental and computational results indicate that the thermodynamically favored Fe-oxygenated intermediates dominate the hydroxylation of the aromatic compounds. A possible mechanism for the hydroxylation is also proposed. Three FeI–FeI organometallic complexes were synthesized and used as highly selective catalysts for the direct hydroxylation of aromatic compounds to phenols, forming FeII–?-O–FeII intermediates as the active oxygen-transfer species.

Posted on 14 January 2015 | 11:10 am

Homoleptic and Heteroleptic Ruthenium(II) Complexes Based on 2,6-Bis(quinolin-2-yl)pyridine Ligands – Multiple-Charged-State Modules for Potential Density Memory Storage

The two ligands 2,6-bis(4-methylquinolin-2-yl)pyridine (L1) and diethyl 2,2?-(pyridine-2,6-diyl)bis(quinolone-4-carboxylate) (L2) were used to prepare the homoleptic [Ru(L2)2][PF6]2 (RU1) and heteroleptic [Ru(L1)(L2)][PF6]2 (RU2) complexes. DFT calculations (B3PW91,3-21G**) performed on both RU1 and RU2 revealed that redox at the ruthenium site for RU2 is less positive by ca. 110 mV. Consequently, the one-electron ligand-based reduction for RU2 is more cathodic by 80 mV. Electrochemistry experiments confirmed that the prediction is qualitatively correct and that the complexes can each hold up to five electrons reversibly. The ligands diethyl 2,2?-(pyridine-2,6-diyl)bis(quinolone-4-carboxylate) (L2) and 2,6-bis(4-methylquinolin-2-yl)pyridine (L1) were used to prepare the homoleptic [Ru(L1)2][PF6]2 (RU1) and heteroleptic [Ru(L1)(L2)][PF6]2 (RU2) complexes. Electrochemistry experiments showed that the complexes can hold up to five electrons reversibly.

Posted on 12 January 2015 | 5:10 pm

The Nature of Hydrogen Production from Aqueous-Phase Methanol Dehydrogenation with Ruthenium Pincer Complexes Under Mild Conditions

A density functional theory (DFT) study was performed to unveil the nature of dihydrogen (H2) production from aqueous-phase methanol dehydrogenation catalyzed by a ruthenium pincer complex. Three catalytic cycles of methanol, formaldehyde, and formate dehydrogenations were investigated at the ?B97X-D/BSI level. The calculated results indicate that the methanol-assisted hydrogen-release step is much more favorable than the direct hydrogen-release one. The dehydrogenation step, the methanol-assisted hydrogen-release step, and the CO2-release step are the rate-determining steps of methanol, formaldehyde, and formate dehydrogenations (stage I, stage II, and stage III), respectively. In addition, the formate dehydrogenation is proposed to be more difficult than the methanol and formaldehyde dehydrogenations according to calculated free-energy profiles. Methanol and formaldehyde dehydrogenation likely follow an outer-sphere mechanism, but formate dehydrogenation could involve both outer-sphere and inner-sphere mechanisms. These results add to our fundamental understanding of this efficient hydrogen-generation reaction from methanol, which could be helpful in the implementation of the methanol/hydrogen economy. A density functional theory (DFT) study unveils the nature of the aqueous-phase methanol dehydrogenation to dihydrogen and carbon dioxide catalyzed by a ruthenium pincer complex. Three catalytic cycles of methanol, formaldehyde, and formate dehydrogenations were investigated.

Posted on 12 January 2015 | 5:10 pm

Synthesis, Structures and Thermal Decomposition of Monomeric Aluminium, Gallium and Indium Silylphosphanides

Monomeric N-heterocyclic carbene (NHC)-stabilized compounds (IMes)R2MP(H)SitBuPh2 (2: M = Al, R = Et; 3: M = Ga, R = Et; 4: M = Ga, R = iPr; 5: M = In, R = Et) have been prepared in moderate yields through the cleavage of four-membered metal phosphine rings like [iPr2GaP(H)SitBuPh2]2 (1) described herein. These compounds were isolated and characterized by means of X-ray crystallographic analysis as well as NMR spectroscopy. On this basis the structural properties, specifically the M–P bond lengths and CNHC–M–P angles, are discussed and compared to literature-known compounds insofar as possible. Proceeding from the cis setting between the phosphorus-bound hydrogen and the metal-bound organic substituent with very low torsion angles, which result in a nearly coplanar arrangement, the results of thermally induced elimination reactions are described. Further, the resulting heterocubane structures 6 and 7 are described. A series of new N-heterocyclic carbene (NHC)-stabilized monomeric metal silylphosphanides of aluminium, gallium and indium were characterized through single-crystal X-ray diffraction and their structural and thermal properties are described.

Posted on 12 January 2015 | 5:10 pm

A Fivefold Interpenetrating dmd Topological Copper(I) Cyanide Complex Formed by C–C Bond Cleavage of Acetonitrile

The solvothermal reaction of a mixture of copper nitrate and 3,5-bis(4-pyridyl)-1H-1,2,4-triazole (4,4?-Hbpt) in a mixed acetonitrile/water solvent leads to a special copper(I) cyanide complex Cu3(CN)3(4,4?-Hbpt)2 (1) with a fivefold interpenetrating dmd topological framework. The cyanide ligands in the structure are generated in situ from the C–C cleavage of acetonitrile under solvothermal conditions. Solid-state luminescence experiments show that 1 can emit efficient violet luminescence, and the possible emission mechanism was investigated in detail through theoretical calculations. The results may be helpful for the design and synthesis of efficient luminescent materials. The copper(I) cyanide complex Cu3(CN)3(4,4?-Hbpt)2 [4,4?-Hbpt = 3,5-bis(4-pyridyl)-1H-1,2,4-triazole] with a fivefold interpenetrating dmd topological framework was synthesized by C–C cleavage of acetonitrile under solvothermal conditions and emits violet luminescence.

Posted on 12 January 2015 | 5:10 pm

Li14(PON3)2O – A Non-Condensed Oxonitridophosphate Oxide

Li14(PON3)2O was synthesized by reaction of phosphoric triamide PO(NH2)3 with LiNH2 at 550 °C. It crystallizes in a trigonal structure [P$\bar {3}$ (no. 147), a = 5.6880(5), c = 8.0855(8) Å, V = 226.55(5) Å3, Z = 1] that can be described as a defect variant of the antifluorite structure type. The crystal structure was elucidated from X-ray powder diffraction data and corroborated by FTIR and solid-state NMR spectroscopy. Li14(PON3)2O is composed of non-condensed PON36– tetrahedra and O2– ions that are surrounded by tetrahedrally coordinated Li+. This is the first example of an ortho-oxonitridophosphate. Li14(PON3)2O, the first ortho-oxonitridophosphate, was synthesized by using a high-temperature deprotonation synthesis and its structure was determined based on X-ray powder diffraction data. It crystallizes in a trigonal structure that can be understood as a defect variant of the cubic antifluorite structure type.

Posted on 9 January 2015 | 12:10 pm

Bifunctional N-Heterocyclic Carbene Ferrocenyl Ligands – Synthesis and Palladium(II) Complexes

Two ferrocenylimidazolium tetrafluoroborate salts [R = Me, 7 and R = (2,4,6-trimethylphenyl), 8], precursors of new ferrocenylimidazol-2-ylidene bifunctional ligands, have been prepared for the first time. The free 1-(2-dimethylaminomethyl)ferrocenyl-3-methylimidazol-2-ylidene (12) was isolated and characterised by 1H and 13C NMR spectroscopy and represents the second example of an isolated and characterised imidazol-2-ylidene directly linked to ferrocene. Neutral (compound 13) and cationic (compound 14) palladium(II) complexes were obtained in moderate yields and characterised by 1H and 13C NMR spectroscopy and mass spectrometry. Two ferrocenylimidazolium tetrafluoroborate salts, precursors of new ferrocenylimidazol-2-ylidene bifunctional ligands, and the corresponding palladium(II) complexes have been prepared for the first time.

Posted on 9 January 2015 | 12:10 pm

An Effective Two-Emulsion Approach to the Synthesis of Doped ZnS Crystalline Nanostructures

The controlled, room-temperature synthesis of M-doped (M = CuII, MnII, SmIII, GdIII, or TbII) ZnS nanostructures (with an average crystallite size of 5–10 nm) in the confined space of miniemulsion droplets is reported herein and discussed. The adopted synthetic route is a colloidal method, ideally suited to easily achieve small particle size and narrow size distribution. The synthesized functional nanostructures crystallize in the sphalerite lattice, as determined by powder X-ray diffraction. In addition to structural characterization, several complementary techniques, such as X-ray photoelectron spectroscopy, thermogravimetric analysis, differential scanning calorimetry, micro-Raman spectroscopy, inductively coupled plasma mass spectrometry, and Fourier transform infrared spectroscopy were used to determine chemical and physical properties as well as the microstructural features of our products. As far as the morphological aspects of the obtained samples are concerned, they were studied by means of scanning and transmission electron microscopies. Finally, the local structure around dopant ions was unravelled by means of X-ray absorption spectroscopy, in particular through extended X-ray absorption fine structure measurements carried out at the Zn, S, and dopant K or L3 edges. This information has been complemented with the investigation of the photoluminescence properties. We report the use of miniemulsions for the controlled synthesis of M-doped (M = CuII, MnII, SmIII, GdIII, or TbII) ZnS nanostructures (with crystallite size of 5–10 nm). The adopted synthetic route is ideally suited to easily achieve small particle sizes and narrow size distribution. The incorporation of the doping ions in the matrix is discussed.

Posted on 8 January 2015 | 11:10 am

Preparation, Characterization, and Thermal Transformation of Poorly Crystalline Sodium- and Carbonate-Substituted Calcium Phosphate

In this paper, we propose a new approach for the preparation of sodium- and carbonate-substituted apatite by a wet precipitation method in aqueous media at 23 °C. The main difference between this method and conventional techniques is that poorly crystalline calcium phosphates are obtained and then heated to form crystalline apatite. The thermal transformations of the samples in the temperature range 80–1000 °C have been determined by temperature-programmed desorption mass spectroscopy and thermogravimetry. The chemical and phase compositions of the sodium- and carbonate-substituted apatite have been studied by inductively coupled plasma (ICP) atomic emission spectroscopy or atomic absorption spectroscopy and X-ray diffraction, respectively. The degree and nature of the carbonate substitution have been determined by CHN analysis and IR spectroscopy, respectively. The samples were subjected to ? irradiation, and the formed radicals were studied by electron paramagnetic resonance (EPR) spectroscopy. SEM has shown nanoparticles (6–12 nm in diameter) with a stability to aggregation under heating to 500–550 °C (increase in size by 30–50?%). Nanoparticles of complex substituted calcium phosphates are obtained by two wet synthesis techniques. The heating of samples to 700 °C causes the formation of Na+- and CO32–-containing apatite. The thermal stability to aggregation at 550–600 °C of the nanoparticles depends on their chemical composition.

Posted on 8 January 2015 | 10:20 am

Oxalate Oxidase Model Studies – Substrate Reactivity

The synthesis and structure of [MnLCl]0.5H2O (1·0.5H2O, HL = 1-benzyl-4-acetato-1,4,7-triazacyclononane) is reported. Complex 1 exists as a coordination polymer in the solid state, and the MnII center is bonded to three amine nitrogen atoms, one carboxylate oxygen atom, a chlorido ligand, and an adjacent carboxylate group in a chelating fashion to afford a seven-coordinate center. The dissolution of 1 in acetonitrile containing excess oxalate (ox) ions results in a monomeric species. When mixtures of 1 and oxalate ions are exposed to oxygen under ambient conditions, a dark pink EPR-silent species is generated. The pink species is believed to be [MnIII(ox)2]–, which results from the displacement of the ligand L– by an oxalate ion. The decomposition of this species ultimately results in the formation of 1 equiv. of CO2 per oxalate ion consumed, a HCO3– ion, and a MnII species. Further reaction of the resulting MnII species with excess oxalate in the presence of oxygen leads to additional oxalate degradation. MnLCl (HL = 1-benzyl-4-acetato-1,4,7-triazacyclononane) is investigated as a structural and functional model for oxalate oxidase. MnLCl effects the catalytic degradation of oxalate ions under ambient conditions. MnLCl is converted to a light-sensitive intermediate during catalysis. Analysis of the reaction mixture indicates that 1 equiv. of CO2 per oxalate ion is produced along with a HCO3– ion.

Posted on 8 January 2015 | 10:20 am

Luminescent Polythiophene-Based Main-Chain Polyoxometalate-Containing Conjugated Polymers with Improved Solar-Cell Performance

New polythiophene-based hybrid conjugated polymers (P2 and P3) containing different amounts of hexamolybdate clusters, which are covalently embedded in the main chain, were successfully synthesized by using the Stille coupling reaction. These soluble hybrid polymers show absorptions in the 400–550 nm range in dilute solutions, which extend beyond 700 nm in thin films. The hybrid polymers are moderately fluorescent in dilute solutions, and the embedded polyoxometalates only partially quench the backbone fluorescence. Simple single-layer photovoltaic cells with a device configuration of ITO/PEDOT:PSS/(P2 or P3)/Ca/Al were fabricated, and a power conversion efficiency of 0.24?% was obtained for P2, which is among the highest values reported for POM-containing hybrid polymers including hybrid diblock copolymers. The first polythiophene-based main-chain polyoxometalate-containing conjugated polymer, synthesized by using the Stille polycondensation reaction, exhibits good photovoltaic properties.

Posted on 8 January 2015 | 10:20 am

pH-Specific Halide-Dependent Materials from ZrIV/Hydroxycarboxylic Acid/Aromatic Chelator Reactivity: Architecture–Lattice Dimensionality and Spectroscopic Fingerprint Relations

The chemical reactivity of binary and ternary ZrIV/hydroxycarboxylic acid/(N,N-aromatic chelator) systems (hydroxycarboxylic acid = citric, malic acid; N,N-aromatic chelator = 1,10-phenanthroline) has been investigated in a pH-specific manner, giving rise to the new binary and ternary crystalline materials [Zr2F6(C6H4O7)2](CH6N3)6·H2O (1), [Zr2F6(C4H3O5)2](NH4)4·3H2O (2), [Zr2(C4H3O5)2(C4H4O5)2(C4H5O5)2](CH6N3)4·4.5H2O (3), and [Zr2(C4H3O5)2(C4H4O5)2(C4H5O5)2](C12H8N2)(C12H9N2)2(CH6N3)2·6H2O (4). Compounds 1–4 were characterized by elemental analysis, FTIR spectroscopy, TGA, 13C-CPMAS, 19F-DPMAS, and 1H CRAMPS NMR spectroscopy, and X-ray crystallography. The structures of 1–4 reveal the influence of fluoride in the starting ZrIV reagents on the identity of the Zr2O2-containing dinuclear assemblies in the arisen 3D architectures. The uniquely defined spectroscopic data, including the NMR data, corroborate the X-ray structures of 1–4 and reflect the contribution of the intra/intermolecular interactions to the structural speciation of the investigated systems. Collectively, the work 1) depicts the factors that determine the nature and properties of the emerging synthetic materials in the investigated systems, 2) formulates structural architecture–lattice dimensionality and spectroscopic fingerprint correlations, and 3) projects the framework through which new ZrIV materials with defined physicochemical properties can arise at the binary and ternary level. The pH-specific reactivity of binary/ternary ZrIV/citric (malic) acid/(phenanthroline) systems leads to inorganic/organic hybrid Zr2O2-containing dinuclear assemblies with distinct 3D architectures. Structural speciation reveals the influence of halide on the ultimate structure and well-defined factor correlations earmarking spectroscopic identity in the design of advanced materials.

Posted on 8 January 2015 | 10:20 am

Structures and Magnetic Properties of Bis(?-phenoxido), Bis(?-phenoxido)-?-carboxylato and Bis(?-phenoxido)bis(?-carboxylato) FeIIINiII Compounds – Magnetostructural Correlations

This report describes the syntheses, characterization, crystal structures and magnetic properties of five dinuclear FeIIINiII compounds derived from two Robson-type tetraiminodiphenol macrocyclic ligands H2L1 and H2L2, which are the [2+2] condensation products of 4-ethyl-2,6-diformylphenol and 1,3-diaminopropane (for H2L1) or 2,2-dimethyl-1,3-diaminopropane (for H2L2). The compositions of the compounds are [FeIII(N3)2L1NiII(H2O)2](ClO4) (1), [FeIII(benzoato)L1NiII(H2O)(?1,3-benzoato)](ClO4) (2), [FeIII(benzoato)L2NiII(H2O)(?1,3-benzoato)](ClO4) (3), [FeIIIL2NiII(?1,3-acetato)2](ClO4)·H2O (4) and [FeIIIL2NiII(?1,3-propionato)2](ClO4)·H2O (5). The bridging moieties between the two metal ions and the azido and carboxylato moieties in these compounds are of the following types: (1) In 1, the bridging moiety is a bis(?-phenoxido) ligand, and two azido ligands are monodentate to the FeIII centre; (2) In 2 and 3, the bridging moiety is a bis(?-phenoxido)-?1,3-benzoato ligand, and the second benzoato ligand is monodentate to the FeIII centre; (3) In 4 and 5, the bridging moiety is a bis(?-phenoxido)bis(?1,3-acetato/propionato) ligand. Variable-temperature and variable-field magnetic data reveal ferromagnetic interactions in 2–5 and an antiferromagnetic interaction in 1 with J values of –9.22 cm–1 for 1, 0.50 cm–1 for 2, 5.65 cm–1 for 3, 13.00 cm–1 for 4 and 14.57 cm–1 for 5. An excellent magnetostructural correlation and interesting structural aspects regarding the bond lengths to the FeIII or NiII centres in some structures have been obtained. The syntheses, characterization, crystal structures and magnetic properties of the FeIIINiII compounds [FeIII(N3)2L1NiII(H2O)2](ClO4) (1), [FeIII(benzoato)L1NiII(H2O)(?1,3-benzoato)](ClO4) (2), [FeIII(benzoato)L2NiII(H2O)(?1,3-benzoato)](ClO4) (3), [FeIIIL2NiII(?1,3-acetato)2](ClO4)·H2O (4) and [FeIIIL2NiII(?1,3-propionato)2](ClO4)·H2O (5; L1, L2 = tetraiminodiphenol macrocycles) are described.

Posted on 8 January 2015 | 10:20 am

Luminescence Enhancement of Lu3TaO7:Eu3+@Lu3TaO7 Red-Emitting Nanophosphors

A series of red-emitting homogeneous Lu3TaO7:Eu3+@Lu3TaO7 (core-shell) nanoparticles have been successfully synthesised for applications in white-light-emitting diodes (WLEDs). The shell-core ratio (SR) was modulated by the amount of core and shell material which gives a depiction of the effect of SR on luminescence intensity. Powder X-ray diffraction data indicate that the core-shell structures of the nanoparticles are homogeneous in the Fm$\bar {3}$m space group. X-ray photoelectron spectroscopy results provide evidence of the core-shell architecture with obvious decreasing amounts of Eu3+ on the surface with an increase in the thickness of the shell. Transmission electron microscopy results showed that by coating the Lu3TaO7 shell on the surface of the Lu3TaO7:Eu3+ core, the particle size increased corresponding to the addition of shell material. The photoluminescence lifetime decays increased and this gives additional evidence of the core-shell structure. Furthermore, the best emission intensity was obtained with a relative optimum shell-core ratio (1/8), showing an increase of 31.5?% compared with the bare core material. A series of red-emitting homogeneous Lu3TaO7:Eu3+@Lu3TaO7 (core-shell) nanoparticles have been successfully synthesised by means of a two-step simple hydrothermal process. The emission intensity was improved by 31.5?% compared with the bare cores and the quantum yield increased by 142?%.

Posted on 8 January 2015 | 10:20 am

Developing Pathways to the Synthesis of Low-Valence Molybdenum Methoxides: Preparation, Characterization, and Redox Chemistry of Dimeric and Tetrameric Molybdenum Alkoxide Clusters

The rare Mo=Mo double-bonded dimeric alkoxide complex [Mo2Cl4(OCH3)4(CH3OH)2] (1) was prepared by the simple methanolysis reaction of [MoCl4(CH3CN)2]. It was shown that the dissolution of 1 in thf results in the formation of the [Mo2O2Cl4(OCH3)2(thf)2] (2) and [Mo2Cl4(OCH3)4(thf)2] (3) dimers. A novel tetranuclear 10e molybdenum cluster [Mo4Cl4O2(OCH3)6(CH3OH)4] (4) was synthesized by the spontaneous disproportionation of 1 in methanol. An alternative pathway to 4 based on the redox reaction of Mo3+ and Mo5+ compounds {in the form of [MoCl3(thf)3] and [Mo2Cl4(OCH3)6] (5), respectively} was proposed and realized. The redox behavior of 4 was investigated by means of cyclic voltammetry. It was demonstrated that 4 may undergo a reversible two-electron reduction process, which implies the retention of the {Mo4} core, whereas the oxidation is irreversible, proceeding apparently with the destruction of the tetranuclear cluster core. A facile synthetic route to the Mo=Mo double-bonded dimer [Mo2Cl4(OCH3)4(CH3OH)2] (1) and its reactivity are described. The redox-active cluster [Mo4Cl4O2(OCH3)6(CH3OH)4] (4) featuring the unique {Mo4} core was obtained through two distinct pathways and characterized in the solid state and in solution by numerous techniques.

Posted on 8 January 2015 | 10:20 am

Tetraaza[14]macrocyclic Transition Metal Complexes as DNA Intercalators

Six tetraazamacrocyclic copper(II) and nickel(II) complexes have been synthesised and their interactions with double-stranded DNA (calf thymus DNA) have been studied using circular and linear dichroism, as well as other spectroscopic methods. The ability of these complexes to intercalate between DNA base pairs has been demonstrated qualitatively and confirmed by determining the stoichiometry and association constant values; these were found to range from 8.5?×?103 – 2.8?×?104 L mol–1. The nickel(II) complexes, being more electron-deficient, seem to have higher binding abilities than guests containing the copper ion. It has also been shown that not only CD, but also linear dichroism, can be a very useful tool for carrying out qualitative DNA interaction studies. This paper describes the synthesis of simple cyclidene-based DNA intercalators. Their ability to bind to DNA was studied using various methods including linear and circular dichroism. The determined binding constants are comparable to those calculated for analogous anthracene and pyrene derivatives.

Posted on 8 January 2015 | 10:20 am

Surface-Selective Deposition of a Reusable Gold Catalyst on a Thin Film of Metal Hydroxide Nanocrystals

We have developed a simple and facile method to fabricate gold nanoparticles (Au NPs) deposited on thin films of layered double hydroxide (LDH) nanocrystals. The oriented thin film of LDH nanocrystals was employed for the preferential deposition of Au NPs by in situ growth of Au NPs on the monolayer thin film of LDH nanocrystals, which effectively provided a large and uniform active hydroxide surface for deposition of a dense monolayer of Au NPs. The reactive hydroxide groups and the positive potential of the LDH surfaces play an important role in the uniform growth of the Au NPs and in their stabilization against agglomeration. This LDH-supported Au NP catalyst exhibits superior catalytic efficiency and reusability without significant loss in conversion efficiency for the reduction of p-nitrophenol with NaBH4, maintaining more than 96?% catalytic conversion efficiency. Uniform gold nanoparticles (Au NPs) are preferentially deposited on the surface of layered double hydroxide (LDH) nanocrystals that densely cover a glass substrate. The LDH surfaces play an important role in the growth of the Au NPs and in stabilizing them against agglomeration. This hybrid film exhibits superior catalytic efficiency and reusability for the reduction of p-nitrophenol with NaBH4.

Posted on 8 January 2015 | 10:20 am

Structure, Thermal Behavior, and Vibrational Spectroscopy of the Silver Borate AgB3O5

The new silver borate AgB3O5 was obtained under high-pressure, high-temperature conditions at 3 GPa and 600 °C in a Walker-type multianvil device. The compound crystallizes with four formula units (Z = 4) in the unit cell in the orthorhombic space group Pna21 (no. 33). The lattice parameters are a = 1029.7(2), b = 832.2(2), c = 390.00(8) pm, and V = 0.3342(2) nm3. The new non-centrosymmetric structure is built up from planar BO3 groups and BO4 tetrahedra, which are interconnected by two- and threefold-coordinated oxygen atoms. In the channels down the c axis, the silver ions are 4+4-fold coordinated by oxygen ions. In addition to the collection of a single-crystal X-ray diffraction data set, ambient- and high-temperature X-ray powder diffraction experiments as well as IR and Raman spectroscopy were performed. The vibrational spectra were interpreted though calculations of the harmonic vibrational frequencies at the ? point. During investigations of the Ag–B–O system, we found the light-stable, non-centrosymmetric silver borate AgB3O5. It is built from corner-sharing BO3 and BO4 groups, which form a three-dimensional structure. Three BO4 tetrahedra share a common, threefold-coordinated oxygen atom in bands that are interconnected by the BO3 groups.

Posted on 8 January 2015 | 10:20 am

Different Contributions of Aliphatic and Conjugated Organic Cations to Both the Crystal and Electronic Structures: Three Hybrid Iodoargentates Showing Two Isomers of the (AgI2)– Chain

Three new hybrid iodoargentates (H2pipe)0.5(?-AgI2) (1), (Me2teda)0.5(?-AgI2) (2), and (H2dpe)0.5(?-AgI2) (3) have been synthesized under solvothermal conditions, whereby the aliphatic organic cations (H2pipe)2+ and (Me2teda)2+ (pipe = piperazine, teda = triethylenediamine) and the conjugated organic cation (H2dpe)2+ [dpe = 1,2-di(4-pyridyl)ethylene] exhibit different contributions to both the crystal and electronic structures. The (H2pipe)2+ and (Me2teda)2+ cations direct the formation of ?-type (AgI2)– polyanionic chains and influence the bandgaps of 1 and 2 indirectly by modulating the iodoargentate anionic structures. By contrast, the (H2dpe)2+ cation directs the formation of a novel ?-type (AgI2)– chain and changes the bandgap of 3 directly to make up the bottom of the conduction band. From 1 and 2 to 3, a direct to indirect bandgap transformation and reduced bandgap can be observed (3.74, 2.88, and 1.99 eV for 1–3, respectively). Relative to the bandgap of bulk AgI2, the bandgaps of 1 and 2 show a blueshift as a result of the quantum confinement effect, whereas the bandgap of 3 shows a redshift owing to the direct participation of the conjugated cation (H2dpe)2+ in adjusting the bandgap. Three new hybrid iodoargentates that show two isomers of 1D (AgI2) anionic chains have been synthesized under solvothermal conditions. Studies indicate that aliphatic and conjugated organic cations have different contributions to both the crystal and electronic structures.

Posted on 23 December 2014 | 11:10 am

Five-Coordinate Indium(III) Porphyrins with Hydroxy and Carboxy BODIPY as Axial Ligands: Synthesis, Characterization and Photophysical Studies

A new series of dyads (TPP)In–O–BDP and (TPP)In–OOC–BDP comprising an indium tetraphenylporphyrin (TPP)In–Cl axially substituted with different boron dipyrrin (bodipy) chromophores are reported. Both compounds were synthesized by the reaction between (TPP)In–Cl and corresponding bodipy units in the presence of a NaH base. Two reference compounds (TPP)In–O–Ph and (TPP)In–OOC–Ph have also been synthesized in order to compare their photophysical and electrochemical properties with the final dyads. The photophysical properties of the compounds were investigated by UV/Vis and fluorescence spectroscopy studies at room temperature as well as at 77 K. Fluorescence spectra suggest weak excited state interactions between the bodipy chromophore and the indium–porphyrin unit. The electrochemical as well as the 1H NMR and 13C NMR spectroscopic data also support the formation of the dyads (TPP)In–O–BDP and (TPP)In–OOC–BDP. Furthermore, DFT and TDDFT calculations were carried out to obtain insight into the electronic properties of the dyads. A comparative study of a new five-coordinate indium(III) porphyrin containing BODIPY as the axial ligand that binds through two different modes: a phenolate and benzoate mode is presented. Both dyad hybrid materials are fully characterized and studied by photophysical experiments.

Posted on 23 December 2014 | 11:10 am

Scorpionato Halide Complexes [(TpPh,Me)Ni–X] [X = Cl, Br, I; TpPh,Me = Hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate]: Structures, Spectroscopy, and Pyrazole Adducts

Pseudotetrahedral scorpionato halide complexes [(TpPh,Me)Ni–X] [TpPh,Me = hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate] were synthesized by metathesis of Tl(TpPh,Me) and NiX2 (X = Cl, Br, I). Pyrazole adducts [(TpPh,Me)Ni(HpzPh,Me)(X)] (X = Cl, I) were also obtained. [(TpPh,Me)Ni–X] (X = Br, I) are isomorphous with previously reported [(TpPh,Me)Ni–Cl], and a new solvated pseudo-polymorph [(TpPh,Me)Ni–Cl]·2CH2Cl2 was found in this work. Ni–X bond lengths correspond to ionic radii of the halide ions, but some variations in Ni–Cl and Ni–N bond lengths are respectively attributed to bending of the chloride from the ideal threefold HB···Ni axis and to the size of the 3-pyrazole substituents. Electronic spectra were rationalized by means of time-dependent (TD) DFT calculations on simplified C3v-symmetric [(Tp)Ni–X] models. Exogenous pyrazole binds to give the pentacoordinate adducts [(TpPh,Me)Ni(HpzPh,Me)(X)] (X = Cl, I). We obtained a crystal structure of the iodide adduct, as well as that of [(TpPh,Me)Ni(HpzPh,Me)(Cl)]·0.5MeCN, isomorphous with a previously reported aquo monosolvate. A hallmark of adduct formation is an intramolecular N–H···X hydrogen bond between the added pyrazole and the adjacent halide ligand, thus giving rise to a strong IR absorption band. The stretching frequency correlates to the N(H)···X separation for the range of known adducts. Pseudotetrahedral scorpionato halide complexes [(TpPh,Me)Ni–X] [X = Cl, Br, I; TpPh,Me = hydrotris(3-phenyl-5-methyl-1-pyrazolyl)borate] and pentacoordinate pyrazole adducts [(TpPh,Me)Ni(HPzPh,Me)(X)] (X = Cl, I) were synthesized, characterized by X-ray crystallography and spectroscopy, and simulated by density functional calculations. Analyses of the structures, spectroscopy, and bonding are discussed with respect to the different halides.

Posted on 23 December 2014 | 11:10 am

Remarkable Selectivity and Photo-Cytotoxicity of an Oxidovanadium(IV) Complex of Curcumin in Visible Light

Oxidovanadium(IV) complexes of 2-(2?-pyridyl)-1,10-phenanthroline (pyphen), viz. [VO(pyphen)(acac)](ClO4) (1), [VO(pyphen)(anacac)](ClO4) (2) and [VO(pyphen)(cur)](ClO4) (3), where acac is acetylacetonate (in 1), anacac is anthracenylacetylacetonate (in 2) and cur is curcumin monoanion (in 3) were synthesized, characterized and their photo-induced DNA cleavage activities and photo-cytotoxicities studied. The complexes are 1:1 electrolytes in DMF. The one-electron paramagnetic complexes show a d-d band near 760 nm in DMF. Complexes 2 and 3 are blue and green emissive, respectively, in DMSO. The complexes exhibit irreversible VIV/VIII reductive responses near –1.1 V and VV/VIV oxidative responses near 0.85 V vs. SCE in DMF–0.1 M TBAP. Complexes 2 and 3 display significant and selective photo-cytotoxicity upon irradiation with visible light giving an IC50 value of about 5 ?M against HeLa and MCF-7 cancer cells; they are significantly less-toxic against normal 3T3 control cells and in the absence of light. Complex 1 was used as a control. Both cytosolic and nuclear localization of the complexes were observed on the basis of fluorescence imaging. The complexes, avid binders to calf thymus (ct) DNA, were found to photocleave supercoiled pUC19 DNA upon irradiation with near-IR light (785 nm) by generating hydroxyl radical (·OH) as the reactive oxygen species (ROS). Cell death events noted with HeLa and MCF-7 cell lines likely are attributable to apoptotic pathways involving light-assisted generation of intracellular ROS. A curcumin oxidovanadium(IV) complex of pyphen is a potent metal-based cytotoxin capable of inducing remarkable ROS-mediated apoptotic photo-cytotoxicity triggered by visible light (400–700 nm). This toxicity is selective for HeLa and MCF-7 cancer cells relative to 3T3 control cells and is absent in the absence of light.

Posted on 23 December 2014 | 11:10 am

Anisotropic ?-Fe2O3@TiO2 Core–Shell Nanoparticles and Their Smart Electrorheological Response

?-Fe2O3@TiO2 core–shell nanoparticles were prepared through a combination of reflux and hydrolysis methods. Firstly, a spindle-like and monodispersed ?-Fe2O3 nanorod core was fabricated by using a reflux method. In the second step, an amorphous TiO2 shell was coated onto the surface of the nonspherical ?-Fe2O3 core with a uniform thickness by means of a controlled hydrolysis method. The morphology, structure, and electrorheological (ER) activity of ?-Fe2O3@TiO2 core–shell nanoparticles were determined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), magnetic testing, and by using a rotational rheometer. The resulting nonspherical core–shell nanoparticles possess the advantages of uniform sizes, weak magnetism, and smart electrorheological behavior. An enhanced ER effect is found with the ?-Fe2O3@TiO2 and hollow TiO2 ER suspension compared with that of a pure ?-Fe2O3 ER suspension. ?-Fe2O3@TiO2 core–shell nanoparticles were synthesized by means of a controlled hydrolysis method and can be used as smart electrorheological (ER) materials. The nonspherical core–shell nanoparticles possess uniform sizes and weak magnetism. The ?-Fe2O3@TiO2 ER suspension exhibits an enhanced electrorheological effect compared with that of a pure ?-Fe2O3 ER suspension.

Posted on 23 December 2014 | 11:10 am

Sn6[P12N24] – A Sodalite-Type Nitridophosphate

Sn6[P12N24] was synthesized from Sn and HPN2 at 820 °C in an evacuated silica glass ampoule. According to powder X-ray diffraction investigations and Rietveld refinement [space group I$\bar {4}$3m (no. 217), a = 8.2882(2) Å, RP = 0.03645, wRP = 0.04613], Sn6[P12N24] crystallizes with a sodalite-type structure with a reduced occupation factor of 3/4 for the Sn atom at Wyckoff site 8c and an empty Wyckoff site 2a at the center of the ?-cages. The structural results are further corroborated by energy-dispersive X-ray spectroscopy (EDX) analyses, solid-state NMR spectroscopy, and theoretical investigations (DFT), including density of states (DOS), energy/volume, and electron localization (ELF) calculations. The 119Sn Mössbauer spectrum shows a single, quadrupole-split signal for SnII at an isomer shift of 3.05 mm/s. In addition to SiPN3 with a defective wurtzite type of structure, the nitridophosphate sodalite Sn6[P12N24] represents the second ternary nitridophosphate containing only p-block elements. The new pseudobinary nitridophosphate Sn6[P12N24] is synthesized and investigated. The ?-cage of this compound, which crystallizes with the sodalite type of structure, is partially empty, as shown by several experimental and theoretical methods.

Posted on 22 December 2014 | 12:10 pm

Hybrid Material Constructed from Hg(NCS)2 and 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine (TPymT): Coordination of TPymT in a 2,2?-Bipyridine-Like Mode

A unique HgII coordination polymer has been synthesized through the reaction of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) with a stoichiometric mixture of HgCl2 and NH4NCS, thus leading to the formation of a 1D polymeric heteroleptic hybrid material [{Hg(NCS)2}2TPymT]n (1). Two coordination pockets of TPymT in 1 are each coordinated to two HgII cations in an unprecedented 2,2?-bipyridine-like mode. Reaction of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) with a mixture of HgCl2 and NH4NCS leads to the formation of a polymeric heteroleptic hybrid material [{[Hg(NCS)2]2TPymT}n], in which two coordination pockets of TPymT are each coordinated to two HgII cations in an unprecedented 2,2?-bipyridine-like mode.

Posted on 22 December 2014 | 12:10 pm

Computational Insights into the Isomerism of Hexacoordinate Metal–Sarcophagine Complexes: The Relationship between Structure and Stability

The hexacoordinate complexes that the macrobicyclic ligands {(NH3)2sar}2+ and {(NMe3)2sar}2+ (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) form with transition metals such as CoIII, CoII and CuII can adopt several isomeric structures. In this article, we have firstly employed DFT methods to compute the relative stability of their ?-ob3, ?-ob2lel, ?-lel2ob and ?-lel3 isomers, as well as the activation barriers for their interconversion. In agreement with the experimental data, the results show that, in general, the different isomers of the CoIII and CoII complexes present similar free energies, whereas the CuII complexes show a strong tendency towards the lel3 form. In addition, the interplay between the structure and stability of these species has been studied by combining shape maps with a distortion/interaction energy analysis. In contrast to the geometries close to the ideal octahedron that all the studied Co complexes present, the lel3 structures of [Cu{(NH3)2sar}]4+ and [Cu{(NMe3)2sar}]4+ are better described as trigonal prisms. In such structures the ligand adopts a conformation significantly more stable than in the other isomers, and this drives the formation of lel3-[Cu{(NH3)2sar}]4+ and lel3-[Cu{(NMe3)2sar}]4+. Overall, the results show a clear relationship between the stability of a given isomer and its degree of distortion with respect to the ideal octahedron (or trigonal prism), with the latter being ultimately dependent on the transition metal and its radius. The relative stability of the isomers of {M(NR3)2sar}2+ (M = CoIII, CoII, CuII; R = H, Me; sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) was studied by means of DFT calculations. Further combination of distortion/interaction analysis and shape maps revealed its relationship with the degree of distortion with respect to the ideal octahedron, which is ultimately dictated by the metal.

Posted on 22 December 2014 | 12:10 pm

Biomimetic Hydroxylation Catalysis Through Self-Assembly of a Bis(pyrazolyl)methane Copper–Peroxo Complex

We synthesised and characterised four copper complexes (with copper in the oxidation states I and II) with the bis(pyrazolyl)methane ligands HC(3-tBuPz)2(Py) and HC(3-tBuPz)2(Qu). With the quinolinyl ligand (2-quinolinyl)bis(3-tert-butylpyrazolyl)methane [HC(3-tBuPz)2(Qu)] we obtained the tetrahedral monofacial complex [CuCl{HC(3-tBuPz)2(Qu)}] (C1) and with the pyridinyl ligand (2-pyridinyl)bis(3-tert-butylpyrazolyl)methane [HC(3-tBuPz)2(Py)] we obtained the three complexes [CuCl{HC(3-tBuPz)2(Py)}] (C2), [CuBr2{HC(3-tBuPz)2(Py)}] (C3) and [CuCl2{HC(3-tBuPz)2(Py)}] (C4), which are also monofacially coordinated. The molecular structures were analysed and compared with density functional theory calculations, which included natural bond orbital (NBO) analysis. C1 can, when generated in situ, serve as part of a precursor, used for the activation of oxygen as tyrosinase model. We observe the self-assembly of a peroxo–dicopper complex P with the HC(3-tBuPz)2(Qu) ligand, which is able to perform catalytic hydroxylation catalysis with phenols. DFT calculations were also carried out to understand the electronic transitions responsible for the UV/Vis bands in the corresponding spectra of the peroxo species. Herein, we present four new bis(pyrazolyl)methane–copper complexes. Furthermore, we studied the self-assembly of a peroxo–dicopper species with catalytic hydroxylation activity of phenols by UV/Vis spectroscopy. The donor competition between pyrazolyl and pyridinyl units as well as the UV transitions of the tyrosinase model have been investigated by density functional theory.

Posted on 22 December 2014 | 12:10 pm

A Technique to Fabricate La2O2CN2:Tb3+ Nanofibers and Nanoribbons with the Same Morphologies as the Precursors

Terbium(III)-doped lanthanum dioxymonocyanamide (La2O2CN2:Tb3+) nanofibers and nanoribbons were fabricated, by the cyanamidation technique, from precursor La2O3:Tb3+ nanofibers and nanoribbons prepared by electrospinning. The morphology of the final products were the same as those of the precursors. X-ray powder diffraction analysis indicated that the crystal phase of La2O2CN2:Tb3+ is tetragonal in space group I4/mmm. SEM analysis revealed that the thickness and width of the La2O2CN2:Tb3+ nanoribbons is about 184 nm and 3.53?±?0.37 ?m, respectively, and the diameter of the La2O2CN2:Tb3+ nanofibers is 175.87?±?16.23 nm at a 95?% confidence level. When excited with a 274 nm ultraviolet light source, the La2O2CN2:Tb3+ nanostructures emit predominantly at 543 nm; this emission originates from the 5D47F5 energy level transition of the Tb3+ ion. It was found that the optimum molar concentration of Tb3+ ions for doping La2O2CN2:Tb3+ nanostructures is 3?%. The La2O2CN2:Tb3+ nanofibers exhibit a higher photoluminescence (PL) intensity than that exhibited by nanoribbons for the same doping concentration. Commission International de l'Eclairage (CIE) analysis demonstrated that color-tuned luminescence can be obtained by changing the concentration of the doping activator ions and the nanostructure morphology. Possible formation mechanisms for the La2O2CN2:Tb3+ nanofibers and nanoribbons are also proposed. More importantly, the new technique employed in this paper and the preparation method are of universal significance for providing other rare earth oxycyanamide nanostructures with various morphologies. Tb3+-doped La2O2CN2 nanofibers and nanoribbons were fabricated by cyanamidation from precursor La2O3:Tb3+ nanofibers and nanoribbons made by electrospinning. The morphologies of the final products were the same as those of their respective precursors. The La2O2CN2:Tb3+ nanostructures are tetragonal in structure with space group I4/mmm and exhibit excellent luminescence performance.

Posted on 22 December 2014 | 12:10 pm

A Click-Functionalized Single-Molecule Magnet Based on Cobalt(II) and Its Analogous Manganese(II) and Zinc(II) Compounds

A mononuclear CoII single-molecule magnet suitable for click chemistry was investigated. [M(oda)(aterpy)] complexes (oda2– = oxodiacetate, aterpy = 4?-azido-2,2?:6?,2?-terpyridine) with M = MnII, ZnII, and CoII were synthesized as azide-functionalized building blocks for the copper-catalyzed azide–alkyne cycloaddition reaction. The required structural integrity of the complexes in solution was proven in great detail by using ESI-MS and NMR spectroscopy. For the six-coordinate [Co(oda)(aterpy)] complex, single-molecule magnet behavior was confirmed with an effective energy barrier of 4.2 cm–1. An azide-functionalized single-molecule magnet suitable for click reactions is reported. The solution stability of three novel building blocks containing single CoII, MnII, and ZnII metal ions is proven in great detail by using ESI-MS and NMR spectroscopy. Remarkably, alternating current susceptibility data of the six-coordinate cobalt(II) complex reveal single-molecule magnet behavior.

Posted on 22 December 2014 | 12:10 pm

1,8-Disubstituted Xanthylidene-Based Remote Carbenes: Photolytic Generation and Isolation of Low-Coordinate Palladium(II) Complex

The isolation and study of carbenes with ?-donating and ?-accepting properties stronger than those of N-heterocyclic carbenes (NHCs) have been regarded as one of the big challenges in carbene chemistry. We have investigated the properties of 1,8-disubstituted xanthylidene-based compounds by using two different approaches: The photolysis-induced formation of free carbenes and the synthesis of the corresponding metal–carbene complexes by oxidative addition. The former study revealed that the carbene unsubstituted at the 1- and 8-positions is kinetically more reactive than the parent xanthylidene and that the substituents at the 1- and 8-positions are less effective in generating carbenes by photolysis. However, oxidative addition of palladium(0) to the 1,8-diphenyl-substituted precursor successfully afforded a low-coordinate 14-electron palladium(II)–carbene complex. This unusual complex is stabilized by agnostic interactions involving an adjacent phenyl group. This complex is the second example of a stable cationic 14-electron palladium(II)–carbene complex to have been reported so far. The photolysis-induced formation of 1,8-disubstituted xanthylidene-based remote carbenes from tosylhydrazone lithium salts has been investigated. The 1,8-unsubstituted carbene was found to be kinetically more reactive than the parent xanthylidene. Oxidative addition of palladium(0) to the chloride precursor facilitated the isolation of a low-coordinate 14-electron palladium(II)–carbene complex.

Posted on 18 December 2014 | 8:41 pm

Catalytic Synthesis of Bi- and Teraryls in Aqueous Medium with Palladium(II) Complexes of 2-(Pyridine-2-ylmethylsulfanyl)benzoic Acid

Suzuki–Miyaura coupling reactions of phenylboronic and 1,4-phenylenediboronic acid with ArBr to form bi- and teraryls have been efficiently catalyzed by the air- and moisture-insensitive complexes [PdCl2L1] [1, L1 = 2-(pyridine-2-ylmethyl)sulfanylbenzoic acid; 0.05–0.5 mol-%] and [Pd(L2-H)2] (2, L2-H = 2-pyridin-2-yl-benzo[b]thiophen-3-ol; 0.01–0.5 mol-%). The complexes were formed by the reaction of [Pd(CH3CN)2Cl2] with L1, and the catalysis proceeds in water for 1. The loading of 0.1–0.5 mol-% of Pd is very promising for the coupling reactions to form teraryls. The COOH group imparts solubility to 1 in water. Ligand L2 is formed by the unprecedented cyclization of L1 in the course of the complexation reaction. The yield of 2 increases with the reaction time (5 h: 70?%; 24 h: 85?%). The two complexes and L1 have been characterized by NMR spectroscopy (1H and 13C{1H}). The single-crystal structures of 1 and 2 have been solved, and the Pd–S, Pd–N, and Pd–O bond lengths are 2.269(2), 1.999(6)–2.057(2), and 1.9787(17) Å, respectively. Nanoparticles (NPs) with a narrow size distribution (ca. 3.0–5.5 nm for 80–85?% of the particles) formed at the start of these reactions and appear to be important for the catalytic coupling. Poisoning experiments and a two-phase test have shown that the catalysis is largely homogeneous and involves [Pd0–PdII] processes. The bond lengths and angles calculated by DFT are consistent with the experimental ones. Complexes [PdCl2L1] [1, L1 = 2-(pyridine-2-ylmethyl)sulfanylbenzoic acid] and [Pd(L2-H)2] (2, L2-H = 2-pyridin-2-yl-benzo[b]thiophen-3-ol) catalyze Suzuki coupling (1 in water) reactions to form bi- and teraryls. L2 forms by an unprecedented cyclization of L1. Pd nanoparticles (NPs) generated in situ play a role in the catalysis, which is a combination of homogeneous and heterogeneous processes.

Posted on 18 December 2014 | 8:41 pm

1,2-Dithiooxalato-Bridged Heterobimetallic Complexes as Single-Source Precursors for Ternary Metal Sulfide Semiconductors

The new 1,2-dithiooxalato-bridged bimetallic Cu–Ga, Cu–In, and Cu–Sn complexes [{(Ph3P)2Cu(?-S2C2O2)}3Ga] (1), [{(Ph3P)2Cu(?-S2C2O2)}3In] (2), [(Ph3P)2Cu(?-S2C2O2)In(S2CNEt2)2] (3), and [{(Ph3P)2Cu(?-S2C2O2)}2Sn(S2C2O2)] (4) were prepared and spectroscopically fully characterized. The crystal structures of 2–4 are presented. Complexes 3 and 4 are potential molecular single-source precursors (SSP) for the ternary semiconductors CuInS2 and Cu2SnS3, respectively, which can be manipulated under ambient conditions. Indeed, a study of the thermal degradation of 3 and 4 revealed that 3 affords pure nanoscaled CuInS2 (mean diameter ca. 2 nm) when the decomposition is carried out in an oleylamine solution by using a hot-injection or arrested-precipitation technique at temperatures well below 250 °C. In contrast, 4 decomposes under the same reaction conditions in an ambiguous manner and forms mixed binary chalcogenide phases. This can be explained by a subtle influence of the relative stability of possible SnII and SnIV intermediates in the case of SSP [{(Ph3P)2Cu(?-S2C2O2)}2Sn(S2C2O2)] (4). Bimetallic single-source precursor complexes for ternary metal sulfide semiconductors are presented. The 1,2-dithiooxalato ligand serves as a linker, complexation site, and molcular source of sulfur in the formation of CuInS2 nanoparticles.

Posted on 18 December 2014 | 8:40 pm

Structural Variation in [PdX2{RE(CH2)nNMe2}] (E = Se, Te; X = Cl, OAc) Complexes: Experimental Results, Computational Analysis, and Catalytic Activity in Suzuki Coupling Reactions

A series of chalcogenoether ligands RE(CH2)nNMe2 (1) [E = Se or Te; R = Ph, o-tol (o-tol = ortho-tolyl), Mes (Mes = 2,4,6-trimethylphenyl); n = 2 or 3] and their palladium complexes [PdX2{RE(CH2)nNMe2}]m [X = Cl (2) or OAc (3); m = 1, 2] were synthesized. Complexes [PdCl2(RECH2CH2NMe2)] [R/E = Ph/Se (2a), Mes/Se (2b), Mes/Te (2c)] were isolated as monomers. Complexes [PdCl2(RECH2CH2CH2NMe2)]m [R/E = Ph/Se (2d), Ph/Te (2e), o-tol/Te (2f)] exist in one monomeric and two dimeric forms in solution; their ratio depends on E and R as revealed by NMR spectroscopic data. Crystal structures of monomeric 2a, 2b, 3b, 2d, 2f, and dimeric 2e were established. Compounds 2a, 2d, 2e, and 2f were also investigated by means of density functional theory (DFT)-based quantum chemical calculations to understand structural variation. The complexes that contained acetate or chalcogenoether ligands with n = 3 showed higher catalytic activity than other derivatives in Suzuki C–C cross-coupling reactions. Complexes [PdX2{RE(CH2)nNMe2}]m (X = Cl, OAc) exist in one monomeric and two dimeric forms in solution depending on E and n. Molecular structures were established by X-ray structural analyses and supported by DFT calculations. These complexes act as catalyst in Suzuki coupling reactions.

Posted on 18 December 2014 | 8:40 pm

Synthesis, Stability and Sensitised Lanthanide Luminescence of Heterobimetallic d/f Terpyridine Complexes

The synthesis, solution behavior and photophysical properties of several heteronuclear bimetallic d/f complexes that utilise a RuII bis-terpyridine moiety as the sensitiser for EuIII, NdIII and YbIII luminescence are reported and compared to a GdIII analogue. The former compounds display sensitised emission in the visible and near-infrared (NIR) regions depending on the choice of the LnIII cation. We illustrate that sensitised lanthanide emission can operate by two distinctly different pathways that involve either the triplet ligand-centred (3LC) excited state of the organic ligand or the triplet metal-to-ligand charge transfer (3MLCT) excited state of the RuII complex. Owing to the electronic structure of this antenna and the higher density of metal-centred accepting states, a higher sensitization efficiency with NdIII was observed than with YbIII and EuIII. Lastly, we have observed unusual sensitised emission from the upper (4F5/2, 2H9/2) excited state of NdIII at approximately 800 nm, which we report here for the first time from a molecular species in solution. The synthesis and solution properties for a series of heterobimetallic RuII–LnIII complexes are reported. These compounds demonstrate the use of a RuII bis-terpyridine unit as the sensitiser for LnIII-based near-infrared emission for the first time. Energy transfer is shown to operate through both the triplet ligand-centred and triplet metal-to-ligand charge-transfer pathways.

Posted on 16 December 2014 | 5:40 pm

Structures and Properties of Luminescent Pentanitratoeuropate(III) Ionic Liquids

A series of luminescent ionic liquids based on pentanitratoeuropate(III) anions combined with imidazolium cations, namely, 1,2,3-trimethylimidazolium {[MC1mim]2[Eu(NO3)5] (1)}, 1,3-dimethylimidazolium {[C1mim]2[Eu(NO3)5] (2)}, 1-ethyl-3-methylimidazolium {[C2mim]2[Eu(NO3)5] (3)}, 1-butyl-3-methylimdazolium {[C4mim]2[Eu(NO3)5] (4)}, 1-hexyl-3-methylimidazolium {[C6mim]2[Eu(NO3)5] (5)}, and 1-methyl-3-octylimidazolium {[C8mim]2[Eu(NO3)5] (6)}, were synthesized. These complexes were characterized by NMR and IR spectroscopy as well as elemental analysis. They exhibit high thermostability and wide liquidus ranges of more than 300 °C. Colorless plate crystals of 1 were isolated, and the crystal structure was determined by single-crystal X-ray diffraction [monoclinic system, C2/c space group with the cell parameters a = 21.6870(6) Å, b = 9.9807(4) Å, c = 15.0267(6) Å, ? = 131.140(4)°, Z = 4]. In the [Eu(NO3)5]2– anion, the 10-coordinate EuIII ion is coordinated by five bidentate nitrate ligands and has a highly symmetrical trigonal-bipyramidal geometry. Compounds 1–6 exhibit bright red luminescence of high colorimetric purity. Only two characteristic narrow monochromatic bands, arising from the 5D07FJ (J = 1 and 2) intraconfigurational f–f transitions, were clearly observed in their emission spectra at 298 K. The intense red photoluminescence is still stable at 150 °C. These 10-coordinated EuIII complexes are of interest as potential thermally stable luminescent soft materials. A series of luminescent ionic liquids based on pentanitratoeuropate (III) anions are synthesized and characterized. These complexes exhibit high thermostability and a wide liquidus range. The 10-coordinate [Eu(NO3)5]2– anion has a highly symmetric trigonal-bipyramidal structure. Complexes 1–6 exhibit bright red luminescence with narrow-band and intense emission of high colorimetric purity.

Posted on 16 December 2014 | 5:40 pm

Iron(II) Spin-Crossover Complexes with Schiff Base Like Ligands and N-Alkylimidazoles

Three new iron(II) spin-crossover complexes with N2O2-coordinating Schiff base like equatorial ligands and alkylimidazole ligands in the axial positions were synthesised. The chain length of the alkylimidazole was varied from the previously published 1 to 5, 7 and 10 carbon atoms to investigate the influence of the alkyl chain length on the spin-transition behaviour in solution and in the solid state. The crystal structures of [1(HeptIm)2] and [1(DecIm)2] (1 = Fe complex with equatorial Schiff base like ligand; HeptIm = N-heptylimidazole, DecIm = N-decylimidazole) and the packing of the molecules in the crystals are discussed. Iron(II) spin-crossover complexes with Schiff base like equatorial ligands and alkylimidazole axial ligands are synthesised. The alkyl chain length is varied from 5 to 7 and 10 carbon atoms. The crystal structures of the C7 and C10 compounds are described. There is an increased cooperativity in spin-crossover behaviour for the compound with the longer C10 alkyl chain than for the C5 compound.

Posted on 16 December 2014 | 12:10 pm

Three Polyoxometalate-Based Coordination Polymers Constructed from the Same Dimetallic Cyclic Building Block

The reactions of silicotungstate, 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo), and copper, cobalt, or nickel acetate under hydrothermal condition yield the three compounds [(SiW12O40)Cu2(3-bpo)2(C5H4NCOOH)2]·H2O (1), [(SiW12O40)Co2(3-bpo)2(C5H4NCOOH)2(H2O)2]·2H2O (2), and [(SiW12O40)Ni2(3-bpo)2(C5H4NCOOH)2(H2O)2]·3H2O (3), respectively, in which the nicotinic acid ligands are generated from the in situ decomposition of 3-bpo during the hydrothermal process. In the three structures, the polyoxometalate (POM) serves as the center and is imbedded within the dimetallic cyclic [M2(3-bpo)2(C5H4NCOOH)2]4+ moiety through coordination bonds to form infinite one-dimensional (1D) supramolecular snadwich-like structures. Owing to the difference in the metal ions, the packing style of [Cu2(3-bpo)2(C5H4NCOOH)2]4+ is different from that of [M2(3-bpo)2(C5H4NCOOH)2]4+ (M = Co, Ni). The electrochemical behaviors of compounds 1–3 were studied by cyclic voltammetry. Three polyoxometalate-based (POM-based) coordination polymers containing a similar type of building block, [M2(3-bpo)2(C5H4NCOOH)2]4+ [M = Cu, Co, Ni; 3-bpo = 2,5-bis(3-pyridyl)-1,3,4-oxadiazole], are hydrothermally synthesized. These polymers are characterized, and their electrochemical behaviors are studied by cyclic voltammetry.

Posted on 15 December 2014 | 11:23 am

Synthesis and Reactions of PdII Complexes with Aryl, Aroyl, and Iminoaroyl Ligands – Insertion of CO and RNC into the Pd–Ar Bond and Intermolecular Coupling of the Ligands

The arylpalladium(II) complexes [PdIAr(bpy)] (Ar = Ph, C6H3-3,5-Me2, C6H4-4-OMe, C6H4-2-OMe, C6H4-4-C6H4-4-I, 1-naphthyl; bpy = 2,2?-bipyridine) undergo insertion of CO and CNR (R = tBu, C6H3-2,6-Me2) into the Pd–aryl bond to produce [PdI(COAr)(bpy)] and [PdI{C(=N–R)Ar}(bpy)]. The dinuclear complex [C6H3-3,5-{(OCH2CH2)2C6H4-3-PdI(bpy)}2] is synthesized by the oxidative addition reaction of 1,3-bis[(3-iodophenyl)-1,4,7-trioxaheptyl]benzene to [Pd(dba)2] (dba = dibenzylideneacetone). The addition of AgBF4 to the arylpalladium(II) complexes [PdIAr(bpy)] (Ar = C6H4-4-OMe, C6H4-2-OMe, 1-naphthyl) produces the intermolecular coupling products of the aryl ligands, Ar–Ar. The reactions of AgBF4 with the aroylpalladium(II) complexes [PdI(COAr)(bpy)] (Ar = C6H3-3,5-Me2, C6H4-2-OMe) result in decarbonylation and intermolecular coupling of the ligands to yield the diarylketones. The iminoaroylpalladium(II) complex [PdI{C(=NtBu)C6H3-3,5-Me2}(bpy)] undergoes hydrolysis of the ligand to yield tBuNHCO(C6H3-3,5-Me2). The addition of AgBF4 to the dinuclear complex [C6H3-3,5-{(OCH2CH2)2C6H4-3-PdI(bpy)}2] yields a mixture of the cyclic oligomers cyclo-[C6H3-3,5-{(OCH2CH2)2C6H4-3-}2]n (n = 1–4) by inter- and intramolecular coupling of the aryl ligands. Aryl-, aroyl-, and iminoaroyl iodidopalladium(II) complexes with a 2,2?-bipyridine ligand react with AgBF4 and H2O to afford biaryls, diarylketones, and arylamides by labilization of the iodido ligand.

Posted on 15 December 2014 | 11:23 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

Mechanistic Insights into Phenol Oxidation by a Copper(II) Complex of a Pyridine- and Amide-Containing Copolymer in an Aqueous Medium

A CuII complex of a pyridine- and amide-containing copolymer (Cu-P1) exhibits effective activity toward phenol hydroxylation in 50?% aqueous methanol solution at apparent pH 8.0 and 25 °C. The complex shows significant first-order rate accelerations of 4.2?×?105 and 1.4?×?105 relative to phenol autoxidation in air and in the presence of 20 mM H2O2, respectively. The reaction mechanisms with H2O2 and air are different on the basis of (a) the different activity profiles for Cu binding, (b) the different deuterium kinetic isotope effects (2.8 in 20 mM H2O2 and 1.2 aerobically), and (c) the formation of a dinuclear substrate–(Cu-P1) complex with H2O2 but a mononuclear one aerobically. The mechanism in the presence of H2O2 is consistent with that of the type-3 dicopper tyrosinase. Although oxidized di-CuII tyrosinase can only use H2O2 for phenol hydroxylation, CuII-P1 can use either air or H2O2 for this process. The studies herein introduce a versatile chemical system for the further exploration of Cu–oxygen chemistry and other types of metal-centered chemistry and for the aerobic degradation of aromatic compounds in environmental and green chemistry. A CuII complex of a pyridine- and amide-containing copolymer catalyzes phenol hydroxylation/oxidation in aqueous methanol at pH 8.0 and 25 °C. First-order rate accelerations by factors of 4.2?×?105 and 1.4?×?105 and deuterium kinetic isotope effects of 2.8 and 1.2, respectively, were observed with and without H2O2. The results suggest that different mechanisms apply for oxidation by O2 and H2O2.

Posted on 7 November 2014 | 11:40 am

Synthetic Strategies for Variably Substituted Ruthenium–Imidazophenanthrolinium Complexes

The synthesis of several symmetric and asymmetric substituted imidazophenanthrolinium ligands and their corresponding ruthenium polypyridyl complexes was achieved by applying a newly designed synthetic concept. By testing different moieties, the advantages and limits of the synthetic approach could be defined. The substitution pattern on the imidazolium moiety has no significant influence on the structural aspects of the imidazophenanthrolinium backbone or on the photophysical properties of the ruthenium compounds. Given that imidazolium salts act as precursors for N-heterocyclic carbenes, the reported results provide the basis for the design of highly efficient oligonuclear photocatalysts. Different synthetic strategies are investigated for the synthesis of variably substituted ruthenium–imidazophenanthrolinium complexes. Structural and preliminary photochemical characterizations suggest that substitution patterns can be altered without influencing the photochemical properties.

Posted on 28 October 2014 | 10:11 pm

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