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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:

Monitoring the Hemolytic Effect of Mesoporous Silica Nanoparticles after Human Blood Protein Corona Formation

The interaction of promising nanoparticles with red blood cells (RBCs) is a critical point to be addressed in nanomedicine and nanotoxicology, and the hemolytic assay is a classical and common test used to evaluate such interactions and the consequent nanoparticle toxicity. In addition, the protein corona is an emergent concept in bionanoscience associated with the manifestation of energetically driven protein–nanoparticle interactions, with a great impact on the nanomaterial toxicity assessment. In the convergence of these two concepts, we evaluated the influence of the formation of the protein corona during the hemolysis induced by spherical mesoporous silica nanoparticles with silanol groups on the external surface (MSN-SiOH), which present a confirmed toxicity on RBCs when they are dispersed as a colloid in phosphate buffer saline solution (PBS). It was observed that human blood proteins such as human serum albumin (HSA), human plasma (HP), hemoglobin (Hb), and RBC lysate, termed hemolysate (HL), can suppress the hemolytic effect induced by MSN-SiOH in a dose-dependent manner. The EC50 values of hemolysis suppression were 24, 8.0, 19, and 28 ?g?mL–1 for HSA, HP, Hb, and HL, respectively. This work thus shows that the results of the hemolytic assay that defines the toxicity and bioreactivity of silica nanoparticles (and others) must be interpreted as a function of the formation of the protein corona. The potential toxicity of protein-corona-coated nanoparticles is mitigated as a result of the steric and electrosteric barriers generated by adsorbed proteins, which largely prevents new interactions between the bare surface of the nanoparticles and red blood cell (RBC) membranes.

Posted on 26 August 2015 | 11:50 am

Covalent Attachment of Thiophene Groups to Polyoxomolybdates or Poly­oxotungstates for the Formation of Hybrid Films

A novel bisphosphonate ligand bearing a thiophene group (AleThio) was synthesized and its covalent grafting to polyoxometalates (POMs) investigated. The hybrid polyoxomolybdate [(Mo3O8)4(O3PC(O)(C3H6NH2CH2C4H3S)PO3)4]8– [Mo12(AleThio)4] was synthesized in water by the reaction of Na2MoO4 with AleThio. It is built of four {MoVI3O8} units connected by phosphonate groups around a central Na+ ion. The reaction of the trivacant [PW9O34]9– units with CoII or NiII ions in the presence of AleThio led to the sandwich-type anions [(PW9O34)2(OH)2(H2O)4M7(O3PC(O)(C3H6NH2CH2C4H3S)PO3)2]14– [M = Ni, Co; M7(AleThio)2]. Salts soluble in organic solvent were prepared by cation-exchange with bis(triphenylphosphine)iminium ions. 31P NMR spectroscopy showed that Mo12(AleThio)4 is stable in acidic medium (pH ? 4) while the M7(AleThio)2 POMs are stable in alkaline medium (6 ? pH ? 13). Their cyclovoltammograms were recorded in solution. Attempts to surface immobilize the POMs through homo-polymerization were unsuccessful but co-polymerization employing 3-methylthiophene led to polymeric films with covalently attached POMs. A bisphosphonate ligand functionalized by a thiophene group has been covalently grafted to a polyoxomolybdate and Co- and Ni-containing polyoxotungstates. The hybrid polyoxometalates have been copolymerized with 3-methylthiophene.

Posted on 26 August 2015 | 11:50 am

Synthesis, Structural Features, Cytotoxicity, and Magnetic Properties of Colloidal Ferrite Spinel Co1–xNixFe2O4 (0.1???x???0.9) Nanoparticles

Colloidal ferrite spinel nanoparticles (CoxNi1–xFe2O4) were prepared by a microwave-stimulated Bradley technique under nonhydrolytic conditions. The effect of Ni2+ doping on the structural properties was studied by powder XRD. The particle size, hydrodynamic size, and morphology were evaluated by transmission electron microscopy (TEM) and dynamic light scattering (DLS), which showed mean crystallite sizes of ca. 10 and 60 nm for powder and colloidal suspensions of CoxNi1–xFe2O4, respectively. The cytotoxicity of the nanoparticles was tested against murine macrophages J774.E, osteosarcoma D17 cells, and human red blood cells (RBCs). The adsorption of bovine serum albumin (BSA) was studied, and the BSA showed a high affinity for the surface of the nanoparticles. The CoxNi1–xFe2O4 nanoparticles in colloidal suspension showed dose-dependent cytotoxicity against all of the studied cell lines, and less harmful effects were observed against RBCs at concentrations of up to 0.1 mg/mL. The cytotoxicity towards the D17 and J774.E cells suggests that internalization by the living cells seems to be the key step to elicit the toxic response. Thus, the cytotoxicity of the particles under investigation seems to be cell-type-dependent and not uniform. The CoxNi1–xFe2O4 colloids exhibited superparamagnetic behavior with blocking temperatures (TB) below 300 K. The magnetic characteristics are well preserved in colloidal form and are similar to those of the powdered ferrites. Co1–xNixFe2O4 nanoparticles are produced by a modified Bradley synthesis. The ferrite particles exhibit superparamagnetic behavior, and Ni2+ substitution has no significant effect on the magnetic response. The cytotoxicity of the ferrites against murine macrophages, osteosarcoma cells, and red blood cells is dose-dependent. The particles do not induce hemolysis at concentrations of up to 0.1 mg/mL.

Posted on 26 August 2015 | 11:50 am

Anchoring of Diphenylphosphinyl Groups to NH2-MIL-53 by Post-Synthetic Modification

Incorporation of new functionalities into metal–organic frameworks (MOFs) by post-synthetic modification is a most attractive strategy for attaining the desired properties without risking destruction of the crystalline structure chosen for the aimed application. In this work the amine group in NH2-MIL-53(Al) was used as anchoring point for the diphenylphosphinyl (Ph2PO–) moiety. The success of the derivatization was confirmed by 31P MAS NMR and DRIFT spectroscopic studies. A newly synthesized reference linker bearing the same phosphinic amide functional group was used to assist in the MOF characterization. The introduction of the bulky diphenylphosphinyl group stabilizes the large-pore form of the MOF and leads to changes in the optical properties as a consequence of the electronic influence of the PO group. The approach described here is relevant for the preparation of novel phosphorus-containing MOFs. Diphenylphosphinyl moieties were attached to NH2-MIL-53(Al) by means of post-synthetic modification. The resulting Ph2–NH–P=O– side group stabilizes the large-pore configuration of the metal–organic framework (MOF) and modifies the energetic levels and optical properties of the linker. This strategy can be useful for the preparation of new porous materials for electronics, sensing, or catalysis.

Posted on 25 August 2015 | 12:10 pm

Synthesis and Characterization of Fluorinated ?-Ketoiminate Zinc Precursors and Their Utility in the AP-MOCVD Growth of ZnO:F

A novel family of zinc bis(?-ketoiminate) complexes 2b–2h have been synthesized by reaction of the isolated free ligands 1a–h with dimethylzinc. The isolated zinc complexes were characterized by elemental analysis, NMR spectroscopy, and in the case of 2b–d and 2f–h, the molecular structures of the complexes were determined by single-crystal X-ray diffraction which reveals the compounds to be pseudo-octahedral six-coordinate, monomeric homoleptic complexes in the solid state. TG analysis showed complexes 2b–f all to have residual masses at 400 °C of 10?% or less, well below the value for ZnO and thus indicative of volatility. Of these systems 2b [Zn{MeC(O)CHC(NCH2CH2OMe)CF3}2] has been investigated for its utility in the AP-MOCVD growth of F-doped ZnO (ZnO:F) in the absence of additional oxidant at 400 °C on glass and silicon substrates. A family of novel bis(?-ketoiminate) zinc precursors baring ether functionalized side arms, have been developed and evaluated for their use in the atmospheric pressure metal organic chemical vapor deposition growth of zinc oxide thin films. Fluorine doped ZnO thin films with a preferred orientation were grown on Si(100) and glass substrates.

Posted on 24 August 2015 | 10:10 am

Graphical Abstract: Eur. J. Inorg. Chem. 24/2015

Posted on 21 August 2015 | 1:18 pm

Unexpected Reactivity of Red Phosphorus in Ionic Liquids (Eur. J. Inorg. Chem. 24/2015)

The cover picture shows the enhanced reactivity of red phosphorus in the employed ionic liquid. Dissolved iodine molecules (yellow spheres) etch red phosphorus, which results in either molecular iodides, for example PI3, or phosphorus nanoparticles. The formation of the different species is monitored by liquid- (top) and solid-phase (bottom) NMR spectroscopy. Details are discussed in the article by M. Ruck, E. Brunner et al. on p. 3991 ff. For more on the story behind the cover research, see the Cover Profile.

Posted on 21 August 2015 | 1:18 pm

Masthead: Eur. J. Inorg. Chem. 24/2015

Posted on 21 August 2015 | 1:18 pm

Unexpected Reactivity of Red Phosphorus in Ionic Liquids

Invited for the cover of this issue are the groups of Michael Ruck and Eike Brunner at the Technische Universität Dresden, Germany. The cover image shows the enhanced reactivity of red phosphorus in the employed ionic liquid. Dissolved iodine molecules (yellow spheres) etch red phosphorus to form either molecular iodides like PI3 or phosphorus nanoparticles. The formation of the different species is monitored by liquid- (top) and solid-phase (bottom) NMR spectroscopy. In our case, the formation of phosphorus nanoparticles was totally unexpected...Read more about the story behind the cover in the Cover Profile and about the research itself on p. 3991 ff.

Posted on 21 August 2015 | 1:18 pm

Affecting the Catalytic Activity of the Known [Ru(tpy)(bpy)(OH2)]2+ Complex in Water Oxidation by Utilization of a Hangman Ligand

[Ru(tpy)(bpy)(OH2)]2+ (bpy = 2,2?-bipyridine, tpy = 2,2?;6?,2?-terpyridine) is the archetype of many known single-site ruthenium complexes used for catalytic water oxidation. Its efficiency is likely influenced by installing a proton-donor/acceptor functionality in proximity to the catalytic site because the reaction mechanism is believed to occur by nucleophilic attack of a water molecule on a high-valent metal–oxo species assisted by hydrogen-bonding interactions. We present herein the results of a study of a new metal complex based on the “hangman” motif that possesses a carboxylic functional group close to the ruhenium center. This catalyst was synthesized in very good yield and fully characterized. We discovered that its catalytic activity was in fact hampered by the presence of the functional group. Further investigations revealed a strong dependence of the catalytic performance not only on the solvent, but also on the counter ion and other additives used. A ruthenium-based hangman complex has been synthesized and tested in catalytic water oxidation. Experiments using cerium(IV) ammonium nitrate as oxidant in aqueous solution revealed that a mismatched pH retards oxygen evolution in comparison with the unfunctionalized parent compound.

Posted on 21 August 2015 | 10:30 am

New Insight into a Deceptively Simple Reaction: The Coordination of bpy to RuII–Carbonyl Precursors – The Central Role of the fac-[Ru(bpy)Cl(CO)3]+ Intermediate and the Chloride Rebound Mechanism

This work demonstrates how a careful reexamination of well-trodden fields can fill conceptual gaps that previously escaped full understanding. The coordination of 2,2?-bipyridine (bpy) to the known RuII–chlorido–carbonyl precursors – the dinuclear [RuCl2(CO)3]2 (P1) and the polymeric [RuCl2(CO)2]n (P2) – has been investigated by several groups in the past, and a remarkably large number of ruthenium–mono(bpy)–carbonyl compounds were identified and fully characterized. Many were investigated as catalysts or key intermediates for the photochemical, electrochemical, and photo-electrochemical reduction of CO2, and for the water–gas shift reaction. Nevertheless, even though most – if not all – of the reaction products are known already, a careful examination of the literature led us to believe that a convincing general scheme interconnecting them all was still missing and important questions remained unanswered. For this reason, we investigated the reactivity of two mononuclear RuII–carbonyl–dmso precursors, trans,cis,cis-[RuCl2(CO)2(dmso-O)2] (P3) and fac-[RuCl2(CO)3(dmso-O)] (P4) – which can be considered as “activated forms” of P2 and P1, respectively – towards the coordination of bpy. Compounds P3 and P4 allowed us to gain new mechanistic insight and a deeper level of understanding. In particular, we found that coordination of bpy to P4 (or P1) generates first the tricarbonyl cation fac-[Ru(bpy)Cl(CO)3]+. This key intermediate undergoes the facile and selective nucleophilic attack on the CO trans to Cl (by RO– in alcoholic solvents or OH– from adventitious water in other solvents), leading to all other species. We also demonstrated that Cl– – even when in large excess – is unable to replace a carbonyl on fac-[Ru(bpy)Cl(CO)3]+. However, the chloride set free from the precursor competes efficiently with bpy for the coordination to RuII (chloride rebound mechanism). This manuscript reinvestigates the coordination of 2,2?-bipyridine (bpy) to RuII–chlorido–carbonyl precursors. A thorough review of the literature data is followed by our original results and a detailed discussion that wraps up old and new results in a comprehensive frame and shows that the coordination of diimines to RuII–carbonyl precursors has a more complex mechanism than anticipated.

Posted on 21 August 2015 | 10:30 am

Ruthenium(II) and Iridium(III) Complexes Bearing Phosphinepyridonate and Phosphinequinolinolate Chelates

Straightforward preparation of five-membered P,N and P,O prochelates was easily achieved from 6-methyl-2-pyridinol and 2-quinolinol. From these ligands, access to the corresponding well-defined ruthenium(II) and iridium(III) complexes was investigated. Owing to the hemilability as well as the reversible proton-responsive character of these chelates, the resulting well-defined ruthenium complexes exhibit interesting activities in hydrogenation. Well-defined ruthenium(II) and iridium(III) complexes featuring five-membered P,N and P,O chelates were synthesized. Owing to the hemilability as well as the reversible proton-responsive character of these chelates, the resulting ruthenium complexes exhibit interesting activities in hydrogenation.

Posted on 20 August 2015 | 2:10 pm

Toxicity and Protective Effects of Cerium Oxide Nanoparticles (Nanoceria) Depending on Their Preparation Method, Particle Size, Cell Type, and Exposure Route

Nanoceria (cerium oxide nanoparticles) toxicity is currently a concern because of its use in motor vehicles in order to reduce carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons in exhaust gases. In addition, many questions arise with respect to its biomedical applications exploiting its potential to protect cells against irradiation and oxidative stress. Indeed, toxicology studies on nanoceria report results that seem contradictory, demonstrating toxic effects in some studies, protective effects in others, and sometimes little or no effect at all. The variability in the experimental setups and particle characterization makes these studies difficult to compare and the toxicity of newly developed nanoceria materials challenging to predict. This microreview aims to compare the toxicity of nanoceria in terms of preparation method, particle size, concentration, host organism, and exposure method. Nanoceria has attracted a lot of attention for biomedical applications thanks to its radiation-protecting, UV-protecting, and antioxidative properties. However, many studies report toxic effects for nanoceria. This microreview aims to compare the toxicity of nanoceria in terms of preparation method, particle size, concentration, host organism, and exposure method.

Posted on 20 August 2015 | 2:10 pm

Iron Oxide Based Nanoparticles for Magnetic Hyperthermia Strategies in Biological Applications

The use of multifunctional nanoparticles (NPs), usually in the range of 3–100 nm, with their newly discovered properties – such as superparamagnetic (SPM) behaviour, enhancement of activity and selectivity in catalytic processes and localised surface plasmon resonance (LSPR) – offers new technical possibilities for biomedical applications such as magnetic hyperthermia (MH), plasmonic photothermal therapy (PPTT) and enhanced magnetic resonance imaging (MRI). In addition, the small size of NPs presents a unique opportunity to interfere, in a highly localised and specific way, with natural processes involving viruses, bacteria or cells and allows interference in the development of complex diseases like many types of cancer and neuropathies (Alzheimer's, Parkinson's, Kreutzer–Jacobs'). The design of biological applications based on MH is a chemical challenge and core@shell structures are most often used to endow NPs with multifunctional abilities. The success of such MH-based biological applications depends on the magnetic functionality of the core as well as the properties of the surface shell in direct interaction with the biological medium. In this review we will describe the most important methodologies developed to synthesise magnetic core@shell nanostructures and their MH applications. Hierarchical core–shell architectures based on magnetic cores decorated with several agents (polymers, drugs, proteins, etc.) allow for multipurpose applications including magnetic hyperthermia, magnetic resonance imaging (MRI) or tissue engineering within a single design. The designed criteria emerge from the interaction of the nano–bio interface, and the planned therapeutic applications.

Posted on 20 August 2015 | 2:10 pm

Controlling the Microstructure of Isotactic Polypropene by C2-Symmetric Zirconocene Polymerization Catalysts: Influence of Alkyl Substituents on Regio- and Stereocontrol

A combined computational and experimental study was carried out to evaluate control of the microstructure of isotactic polypropene by C2-symmetric zirconocenes with rac-SiMe2[Ind]2-based ligands. Building on the highly regio- and stereospecific catalyst combining 2-Me and 4-Ph substituents, we made further modifications to the ligand framework by systematic addition of alkyl substituents. Propene insertion barriers are given for a total of 24 catalysts. Calculations and experiments show that the series of catalysts produce highly stereoregular isotactic polypropene. Regiocontrol can be markedly improved by addition of 3-Me substituents or by replacing 2-Me with bulkier 2-alkyl substituents on the indenyl ligand, but the former is accompanied by loss of stereocontrol and the latter by significantly increased overall barriers for propene insertion. The combination of methyl substituents and tBu groups on the 4-Ph ligand substituents is shown to provide improved regiocontrol without sacrificing high stereocontrol. Microstructure of polypropene: A series of metallocene catalysts producing highly stereoregular isotactic polypropene is reported. A combined computational and experimental study reveals the dependence of catalytic behavior on ligand substitution pattern.

Posted on 20 August 2015 | 2:10 pm

An Insight into Transfer Hydrogenation Reactions Catalysed by Iridium(III) Bis-N-heterocyclic Carbenes

A variety of [M(L)2(L?)2{?C,C?-bis(NHC)}]BF4 complexes (M = Rh or Ir; L = CH3CN or wingtip group; L? = I– or CF3COO–; NHC=N-heterocyclic carbene) have been tested as pre-catalysts for the transfer hydrogenation of ketones and imines. The conversions and TOF's obtained are closely related to the nature of the ligand system and metal centre, more strongly coordinating wingtip groups yielding more active and recyclable catalysts. Theoretical calculations at the DFT level support a classic stepwise metal-hydride pathway against the concerted Meerwein–Ponndorf–Verley (MPV) mechanism. The calculated catalytic cycle involves a series of ligand rearrangements due to the high trans effect of the carbene and hydrido ligands, which are more stable when situated in mutual cis positions. The reaction profiles obtained for the complexes featuring an iodide or a trifluoroacetate in one of the apical positions agree well with the relative activity observed for both catalysts. The study of a series of iridium(III) bis-NHC complexes in the transfer hydrogenation of imines and ketones shows how slight modifications of the ligand system significantly affect the activity of the active species. Moreover, a catalytic cycle based on DFT calculations and experimental observations has been proposed.

Posted on 19 August 2015 | 2:10 pm

A Pyrazolate-Bridged Bis(pentadentate) Ligand and Its Dinuclear Ruthenium Complex

A new bis(pentadentate) pyrazole-bridged proligand HLbis5 providing two {N5} binding pockets and its diruthenium complex [Lbis5Ru2(MeCN)2](PF6)3 (1) have been synthesized, and the structure of 1 has been elucidated by X-ray diffraction. The two exogenous MeCN ligands in 1 are both directed into the central pocket created by the two metal ion compartments and interfere with each other, which leads to some distortion of the dimetallic framework. According to an Eyring analysis of variable-temperature NMR spectroscopic data, interconversion of the resulting enantiomeric forms is rapid with a free activation energy of ?G? = 43.7 kJ?mol–1 at 298 K (?H? = 30.8 kJ?mol–1, ?S? = –43.2 J?mol–1?K–1). Cyclic voltammetry of 1 shows two sequential reversible oxidations at ca. 0.85 and 1.25 V (vs. SCE), and the mixed-valent RuIIIRuII species has been characterized by spectroelectrochemistry, UV/Vis/NIR and EPR spectroscopy. Complex 1 was found to be a poor catalyst for water oxidation: under standard conditions [triflic acid, pH 1, using cerium(IV) ammonium nitrate as oxidant] rapid degradation by oxidative ligand fragmentation at its benzylic-type CH2 groups was observed. A new pyrazolate-bridged ligand has been developed that can bind two metal ions in two pentadentate compartments, leaving a single site per metal atom for binding of exogenous substrates within the dimetallic pocket. A dinuclear Ru complex illustrates the structural features, dynamics, and electronic coupling induced by the new ligand framework.

Posted on 19 August 2015 | 2:10 pm

Rhenium Complexes of Ligands Based on Stilbene – Synthesis, Characterization, ­Reactivity, and Conformational Analysis

The imine ligand L1 was prepared by the reaction of 4-amino-4?-(dimethylamino)stilbene and 2-pyridinecarbaldehyde. The amine ligand L2 was obtained in good yield by the reduction of L1 with NaBH4. The complexes [ReX(CO)3(Ln)] (1a: X = Cl, n = 1; 1b: X = Br, n = 1; 2a: X = Cl, n = 2; 2b: X = Br, n = 2) were prepared through the reactions of equimolar solutions of the corresponding ligand and [ReX(CO)3(CH3CN)2]. The complexes were characterized spectroscopically, and the structures of 1a and 1b were established by X-ray diffraction. A configurational and conformational study of the amine complex 2b in dimethyl sulfoxide (DMSO) solution was performed through molecular modeling and with the experimental NMR spectroscopy data. The transformations of 2a and 2b into 1a and 1b, respectively, were also monitored by UV/Vis and NMR spectroscopy. Rhenium(I) complexes of amine and imine ligands derived from stilbene are prepared. Configurational and conformational studies of the amine complex are performed through molecular modeling and experimental NMR spectroscopy data. The transformations of the amine complexes to the imine complexes are also monitored by UV/Vis and NMR spectroscopy.

Posted on 19 August 2015 | 2:10 pm

Dissolution of the Rare-Earth Mineral Bastnaesite by Acidic Amide Ionic Liquid for Recovery of Critical Materials

Rare-earth elements provide the cornerstones to clean sustainable energy and modern technologies such as computers, communications, and transportation. As such, the recovery of rare earths (REs) from minerals such as bastnaesite remains important for modern times. As the light lanthanides (La–Nd) constitute the majority (typically >98.7?%) of the REs in bastnaesite with the heavy REs (Sm–Lu) contributing the remainder (approximately 1.3?%), an enrichment of heavier REs may serve as an effective means of assisting rare-earth recovery. Such an extractive metallurgy process involving ionic liquids (ILs) leads to an enrichment of heavy REs by nearly an order of magnitude. The acidic IL N,N-dimethylacetamidium bis(trifluoromethylsulfonyl)imide (DMAH+NTf2–) in the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM+NTf2–) dissolves froth flotation bastnaesite, synthetic bastnaesite analogues (RECO3F), RE2O3, and RE2(CO3)3 minerals. An overall reaction for the dissolution of bastnaesite is proposed for this IL system. This IL system may provide the initial stages of a greater RE separation scheme for bastnaesite froth flotation concentrates. A selective dissolution process has been developed to extract rare-earth metal ions through the use of protic ionic liquids.

Posted on 19 August 2015 | 2:10 pm

Syntheses, Crystal Structures, and Photocatalytic Properties of Polymeric Iodoargentates [TM(2,2-bipy)3]Ag3I5 (TM = Mn, Fe, Co, Ni, Zn)

Five isostructural polymeric iodoargentates incorporating similar transition metal complex cations as structure-directing agents, – namely, [TM(2,2-bipy)3]Ag3I5 [TM = Mn (1), Fe (2), Co (3), Ni (4), Zn (5)] – have been solvothermally synthesized and structurally characterized. The title compounds contain saturated [TM(2,2-bipy)3]2+ cations and one-dimensional (1D) [Ag3I5]2– anionic chains formed by trans-interconnection of [Ag3I5] semicubes through Ag–I bonds. The optical absorption spectra indicate that compounds 1–5 are semiconductors with estimated band gaps of 2.28, 1.87, 1.95, 2.01, and 2.61 eV, respectively, which are mainly ascribed, on the basis of density functional theory (DFT) calculations, to charge transitions between the [Ag3I5]2– anionic chains and organic cationic units. We evaluated the photocatalytic efficiencies of compounds 1, 2, 4, and 5 with regard to the decomposition of crystal violet (CV) under visible irradiation, and the four compounds showed excellent photodegradation abilities in comparison with N-doped P25, with an order of 1 > 2 > 4 > 5 > P25. The luminescent properties and thermal stabilities of the title compounds were also studied. A series of inorganic–organic hybrid iodoargentates – [TM(2,2-bipy)3]Ag3I5 (TM = Mn, Fe, Co, Ni, Zn) – have been solvothermally synthesized and structurally characterized. Their semiconductor nature leads to highly efficient heterogeneous photodegradation activities for crystal violet (CV) under visible light irradiation.

Posted on 19 August 2015 | 2:10 pm

A Very Stable Nickel Broken-Chain Complex with Isolated Ni–Ni Interactions

Two defective nickel-extended metal-atom chain (EMAC) complexes were synthesized from a pyrazine- and naphthyridine-containing ligand and structurally characterized. The chains consist of dinickel and trinickel units with one absent metal center, in spite of which the complexes are very stable. The magnetic interaction between the two terminal, high-spin nickel atoms is very weak with a spin exchange of J = –0.62(3) cm–1. An electrochemical study on one of the defective nickel EMAC complexes showed high resistance to both oxidation and reduction, with one reduction at E1/2 = –0.76 V and no observable oxidation events in the range from –0.9 V to +1.20 V. The pentanickel-extended metal-atom chain [Ni5(?5-dpznda)4Cl2] (H2dpznda = N2,N7-bis(pyrazin-2-yl)-1,8-naphthyridine-2,7-diamine) was synthesized, and its magnetism and conductance were studied. In its linear structure, which is partially delocalized, four ligands are wrapped around the metal string forming the core of the molecule.

Posted on 19 August 2015 | 2:10 pm

Synthesis of CaTiO3 Nanofibers with Controllable Drug-Release Kinetics

Calcium titanate (CaTiO3) nanofibers with controlled microstructure were fabricated by a combination of sol–gel and electrospinning approaches. The fiber morphology has been found to rely significantly on the precursor composition. Altering the volume ratio of ethanol to acetic acid from 3.5 to 1.25 enables the morphology of the CaTiO3 nanofibers to be transformed from fibers with a circular cross section to curved ribbon-like structures. Ibuprofen (IBU) was used as a model drug to investigate the drug-loading capacity and drug-release profile of the nanofibers. It was found that the BET surface area and the pore volume decrease markedly with the utilization of F127 surfactant. The nanofibers synthesized without F127 surfactant present the highest drug-loading capacity and the most sustained release kinetics. This study suggests that calcium titanate nanofibers can offer a promising platform for localized drug delivery. Calcium titanate (CaTiO3) nanofibers with controlled microstructure were fabricated by electrospinning. The nanofibers synthesized without F127 surfactant, which are of markedly increased surface area and pore volume, present the highest drug-loading capacity and the most sustained release kinetics.

Posted on 18 August 2015 | 7:20 pm

Colorimetric Detection of Spermine by the CuII Complex of Imine-Based Organic Nanoaggregates in Aqueous Medium

A Schiff-base receptor bearing different functionalities was synthesized from dipicolinic acid hydrazide and characterized with several spectroscopic techniques. To explore its practical application as a sensor, the receptor was processed into organic nanoaggregates (O1) in aqueous medium by the reprecipitation method. The O1 nanoaggregates were characterized by techniques such as dynamic light scattering and TEM, and their recognition properties for metal ions were investigated by fluorescence spectroscopy. The nanoaggregates showed selectivity for Cu2+ over other metal ions. The structure of the complex O1·Cu2+ thus formed was determined by single-crystal X-ray crystallography. Complex O1·Cu2+ was further employed as a sensor for detection of biogenic amines in aqueous medium, and showed selective sensing of spermine with a detection limit of 7.62 nM. The color change on addition of spermine to the complex can be seen with the naked eye. Moreover, stability in the physiological pH range and negligible effect of ionic environment provided the opportunity for real-time application of the sensor in aqueous medium. A sensor based on the copper complex of imine-based nanoaggregates can be used for nanomolar selective determination of spermine in aqueous samples without interference from any of the potential interferents. The distinct color change can be seen with the naked eye. The sensor can be used for real-time analysis of spermine in various samples.

Posted on 18 August 2015 | 7:20 pm

Asymmetric Oxidation Synthesis of Modafinil Acid by Use of a Recyclable Chiral-at-Metal Complex

The enantioselective oxidation synthesis of chiral modafinil acid and its analogues with high enantiomeric excess has been developed by means of a chiral-at-metal strategy. Treatment of ruthenium complexes cis-[Ru(bpy)2Cl2] or ?/?-[Ru(bpy)2(MeCN)2](PF6)2 (bpy is 2,2?-bipyridine) with the appropriate prochiral thioether ligands afforded thioether complexes rac-1, ?/?-1, rac-2, ?/?-2, rac-3, and ?/?-3. Diastereoselective oxidation of the thioether complexes in situ produced the corresponding sulfoxide complexes rac-1a, ?/?-1a, rac-2a, ?/?-2a, rac-3a, and ?/?-3a. The configuration at the metal center in each case is stable during the coordination and oxidation reactions, and dictates the chirality of the sulfoxide ligand in the oxidation process. The chiral modafinil acids were obtained with ee values greater than 98?% upon their removal from the corresponding sulfoxide complexes in the presence of TFA/MeCN. Moreover, the chiral ruthenium precursors ?/?-[Ru(bpy)2(MeCN)2](PF6)2 are recyclable and reusable with complete retention of the configurations. Chiral modafinil acid and its analogues have been synthesized with high ee values by means of asymmetric coordination oxidation of a thioether complex in situ with a chiral-at-metal strategy.

Posted on 18 August 2015 | 7:20 pm

Mixed-Valent Selenium Ligands in the Uncharged Iridium Complexes [Ir4Se10Br16] and [Ir6Se8Cl30]

The reaction of Ir with Se and SeBr4 at 200 °C yields shiny vermillion slate-like crystals of the new compound Ir4Se10Br16. Single-crystal X-ray diffraction revealed an orthorhombic unit cell, space group Pccn, with lattice parameters a = 1515.0(1) pm, b = 1534.4(1) pm, and c = 1514.5(1) pm at 296(1) K. The crystal structure consists of uncharged tetranuclear iridium complexes [Ir4Se10Br16] with C2 symmetry. In the [(Ir3+)4(?4-?2-Se22–)2(?-?Se-[SeBr]–)2(?Se-SeBr2)4(?-Br–)2(Br–)4] complex, each of the iridium atoms is coordinated octahedrally by four selenium and two bromine atoms. Selenium adopts three different oxidation states: –I in the fourfold-bonded diselenide dumbbell, ±0 in the bridging [SeBr]– unit, and +II in the terminal SeBr2 ligand. An analogous reaction with SeCl4 at 300 °C yields orange air-stable crystals of Ir6Se8Cl30. The triclinic crystal structure [space group P$\bar {1}$, a = 891.2(1) pm, b = 1064.6(1) pm, c = 1263.0(1) pm, ? = 94.458(3)°, ? = 106.900(3)°, and ? = 101.410(3)° at 296(1) K] consists of uncharged hexanuclear iridium complexes with the structured formula [(Ir3+)6(?-?Se-[SeCl]–)2(?Se-SeCl2)6(?-Cl–)10(Cl–)6] and shows structural motifs similar to Ir4Se10Br16 and IrSeCl5. The triclinic structure of IrSeCl5 [P$\bar {1}$, a = 1223.4(1) pm, b = 1408.7(1) pm, c = 1499.5(1) pm, ? = 115.72(1)°, ? = 106.05(1)°, and ? = 96.38(1)° at 296(1) K] is homeotypic to monoclinic RhSCl5. The tetra- and hexanuclear ring-shaped iridium molecules [Ir4Se10Br16] and [Ir6Se8Cl30] are among the largest complexes in the category of halogen-rich chalcogen halides of the platinum-group metals. They feature unusual [SeBr]– or [SeCl]– ligands as well as diverse oxidation states of selenium in one molecule.

Posted on 17 August 2015 | 2:10 pm

Electrochemical, Thermodynamic and Spectroscopic Investigations of CeIII in a 1-Ethyl-3-methylimidazolium Ethyl Sulfate (EMIES) Ionic Liquid

A systematic study was carried out to explore the electrochemical behaviour of Ce in an EMIES ionic liquid at a glassy carbon (GC) electrode over the range 298–351 K. The electrode reaction of CeIII/CeIV was found to be quasi-reversible by cyclic voltammetry. An increase in the current intensity was obtained with an increase in temperature. The diffusion coefficients (Do), the transfer coefficients (?) of CeIII and the charge-transfer rate constants (ks) were estimated. The apparent standard potential (E0*) and the thermodynamic properties of the oxidation of CeIII to CeIV were also investigated. A photoluminescence investigation on cerium extracted in EMIES ionic liquid shows the stabilization of cerium in the CeIII state. There is a broad band at 350 nm, which is attributed to the 5d14f1 transitions. With an increase in temperature the CeIII peak intensity decreases gradually and is almost flattened at 350 K. This may be a result of CeIII being converted into CeIV with an increase in temperature and then not being luminescence-active as it is an f0 system. The electrochemical and thermodynamic behaviour of cerium was investigated in an ionic liquid using a glassy carbon electrode at different temperatures. The data obtained can be used to critically evaluate the ability to use electrochemical methods for controlled, potential-mediated separation of lanthanides and actinides by electroplating on electrode surfaces in ionic liquid media.

Posted on 17 August 2015 | 1:10 pm

Europium Luminescence as a Structural Probe: Structure-Dependent Changes in Eu3+-Substituted Th(C2O4)2·xH2O (x = 6, 2, and 0)

Three different phases of thorium(IV) oxalate hydrate [Th(C2O4)2·xH2O] with different water contents, namely, the hexahydrate, dihydrate, and anhydrous phases, were prepared by thermal treatment of the as-precipitated hydrated thorium(IV) oxalates. With the change in water content, the structure changes from monoclinic (C2/m) for the hexahydrate to monoclinic (C2/c) for the dihydrate and finally to a highly disordered phase for the anhydrous state. The local coordination around the Th4+ ions in these structures was monitored by using Eu3+ ions as luminescent probes. The analyses of the emission spectra owing to the electric-dipole transitions (EDTs) and magnetic-dipole transitions (MDTs) of the Eu3+ ions in the different phases revealed that the site symmetry around the Th4+ ions decreases systematically from symmetric to highly distorted with the decrease in water content. The relative intensity ratios (I) of the EDT to MDT for x = 6, 2, and 0 are 2.36, 3.32, and 4.23, respectively. The analyses of the delay curves corresponding to the 5D0 level of the Eu3+ ions indicated biexponential decay with varying lifetimes, which suggests two possible environments around the Eu3+ ions and a possible role of oxygen vacancies. The long-lived species is expected to be distant from the charge-compensation defects, whereas the short-lived species is nearer to the charge-compensation defect. Tunability of the emission with the excitation wavelength is observed for all phases and is attributed to the presence of defect-mediated broad emission in the blue region and red-orange emission from the Eu3+ ions. The three different structures of Eu3+-doped hydrated thorium(IV) oxalate, Th(C2O4)2·xH2O (x = 6, 2, and 0), are prepared by controlled thermal treatment of the hydrous precipitate of thorium(IV) oxalate, and the structural distortions around the Th4+ ions are investigated through the variation of the luminescence properties of the Eu3+ ions.

Posted on 17 August 2015 | 1:10 pm

Multifunctional Hybrid Silica Nanoparticles with a Fluorescent Core and Active Targeting Shell for Fluorescence Imaging Biodiagnostic Applications

We prepared hybrid nanoparticles with a brightly fluorescent silica core and a biocompatible thermoresponsive polymer shell containing tumor-targeting folic acid (FA) groups. The silica core has a perylenediimide fluorescent dye anchored covalently to the structure for traceability and bioimaging applications. The polymeric shell was synthesized by reversible addition–fragmentation chain-transfer (RAFT) polymerization to guarantee the homogeneous size of the particle shell. The shell is composed of copolymer chains with one block of oligo(ethylene glycol)methacrylate and 2-(2?-methoxyethoxy)ethylmethacrylate with another block of the reactive monomer N-acryloxysuccinimide (NAS). The NAS groups were used to covalently attach a large amount of amino-functionalized FA to the particle shells to provide active targeting properties towards cancer cells and tissues. The targeting capability of the folate-containing nanoparticles was evaluated against NCI-H460 tumor cells, which overexpress folate receptors. The nanoparticles with FA show a higher uptake efficiency compared to that of the equivalent nanoparticles without FA. This result validates the imaging capabilities and active targeting efficiency of our nanoparticles, an important step towards the goal of developing vehicles for precision drug delivery systems that combine therapeutic and diagnostic (theranostic) functionalities with large drug payloads, active targeting, and stimuli-activated drug release. We prepare hybrid nanoparticles with a brightly fluorescent silica core and a biocompatible thermoresponsive polymer shell containing a large amount of folic acid (FA) groups. The active cancer-targeting properties of the FA are evaluated against NCI-H460 tumor cells. The FA-loaded nanoparticles internalize faster and in larger amounts than control counterparts without FA.

Posted on 14 August 2015 | 11:20 am

IR Spectra and DFT Calculations of ­M–?2-(NC)–CH3, CH3–MNC, and CH2=M(H)NC Prepared by Reactions of Laser-Ablated Hf and Ti Atoms with Aceto­nitrile

Laser-ablated Hf and Ti atoms produce M–?2-(NC)–CH3, CH3–MNC, and CH2=M(H)NC in reactions with acetonitrile, parallel to the earlier Zr results, based on isotopic substitution and frequencies computed by DFT. These products are the most stable components in the previously proposed reaction path for reactions of metal atoms with acetonitrile, in line with the observed products in other metal systems and DFT calculations. Other plausible products [CH3CN–M and CH?M(H2)NC] are energetically too high to be generated in reactions of the group 4 metals. The group 4 metals form strong ? complexes with the nitrile group as they do with acetylene and ethylene. The methylidenes are slightly more agostic due to the metal-containing conjugation system than those produced from small alkanes and methyl halides. Relativistic contraction is also evident in that the Hf bonds are shorter than the Zr bonds. The primary products from reactions of laser-ablated Hf and Ti atoms with acetonitrile. Both Hf and Ti form ? complexes [M–?2-(NC)–CH3], which convert into the insertion and methylidene products. The weaker ? and stronger m absorptions in the Hf spectra are in line with their relatively high and low energies, while the observed three products are the most stable steps in the proposed reaction path. The group 4 metal methylidenes are agostic.

Posted on 14 August 2015 | 11:20 am

Extended Threefold-Symmetric Second-Harmonic-Generation Chromophores Based on 1,3,5-Trisubstituted Benzene Complexes

The elongation of the ? system of a donor–?–acceptor (D–?–A) chromophore has often proven to be beneficial for its nonlinear optical (NLO) activity. Against this background, different alkynyl protecting groups such as organosilyl and dicobalt hexacarbonyl functions were investigated with respect to their ability to enable the coordination of an electron-withdrawing CpRu+ fragment (Cp = cyclopentadienyl) to a threefold ethynyl-substituted benzene ring, acting as a potential 2D NLOphore, without undesired side reactions. In addition, the influence of the perpendicularly coordinated CpRu+ unit on the NLO properties was examined. The obtained organometallic triisopropylsilyl-substituted benzene ruthenium complex and the multinuclear dicobalt hexacarbonyl protected ferrocene complex were fully characterized. Owing to the problems during the purification of the trimethylsilyl-protected benzene ruthenium complex and the subsequent deprotection to the free alkyne complex, it was not possible to fully characterize those complexes. The introduction of the CpRu+ fragment was sensitive to the steric demands of the benzene substituents but beneficial for the generation of NLO activity. The first hyperpolarizabilities of the triisopropyl and dicobalt hexacarbonyl complexes were investigated by hyper-Rayleigh scattering. The molecular structures were characterized by X-ray crystallography and infrared (IR) spectroscopy. The structures and IR spectra were compared with Kohn–Sham density functional theory calculations. Synthetic strategies to protect C–C triple bonds from the electrophilic attack of the cationic organometallic complex CpRu+ (Cp = cyclopentadienyl) are examined. The achieved threefold-symmetric chromophores are characterized, and the concept of 3D nonlinear optically active chromophores is corroborated.

Posted on 14 August 2015 | 11:20 am

Substrate-Mediated Deactivation of a Ru(PtBu2NBn2) Cooperative Complex

Ligand design for metal–ligand cooperative (MLC) catalysis is inherently more complex than that for traditional non-cooperative ligands. The basicity, sterics and structure of the acid/base group in MLC proton-transfer (PT) complexes, for instance, undoubtedly influence catalyst performance. Herein, we evaluate the highly tunable PR2NR?2 (1,5-R?-3,7-R-1,5-diaza-3,7-diphosphacyclooctane) ligand family for the first time in an organic transformation. With [Ru(Cp)(PtBu2NBn2)(MeCN)][PF6] as the catalyst, no turnover was observed in the anti-Markovnikov hydration of alkynes, a known PT MLC reaction. Treatment of the cooperative complex with phenylacetylene affords a vinylammonium product in which the pendant nitrogen atom of the PtBu2NBn2 ligand forms a Lewis acid–base adduct with the alpha-carbon atom of the vinylidene intermediate. Characterization by X-ray crystallography and NMR spectroscopy conclusively assign this structure in both the solid and the solution state. The adduct formation is irreversible, and the adduct is characterized as a catalyst deactivation product. Snapping Shut: The PR2NR?2 ligand family (R and R? are removed for clarity in the graphic) open the door for easily tuned catalysts for cooperative organic transformations. However, the ligand swings toward the vinylidene, forming a stable (and catalytically inactive) Lewis acid–base adduct. (? = open coordination site)

Posted on 14 August 2015 | 11:20 am

Ferric Ammonium Citrate – What's in It?

Ferric ammonium citrate (FAC) is administered to humans in drugs or food supplements, but its exact composition and structural features are not known. We report that the major component in commercial FAC-brown and FAC-green is a trinuclear ferric citrate complex, namely [Fe3(cit)4H]6– (1). Complex 1 comprises a dinuclear subunit in which two ferric ions with a 3.122(1) Å separation are bridged by two alkoxido oxygen atoms from two citrate ligands. Two other alkoxido oxygen atoms form a bridge to a third ferric ion completing an Fe3O4 inner core. The compound [Cr(urea)6]2·1·14.5H2O exhibits paramagnetic behavior that corresponds to three magnetically independent high-spin (HS) d5 and two d3 centers. In addition to complex 1, FAC-green also contains a dinuclear ferric citrate complex, namely [Fe2(Hcit)3]3–, in an approximate ratio of 1:1. We eat it, we drink it, and patients swallow multigram quantities of this material, but its compositional and structural properties are unknown. Ferric ammonium citrate is a mixture of several species, and the dominant one is a trinuclear iron citrate complex, [Fe3(cit)4H]6–.

Posted on 12 August 2015 | 10:20 am

Selective [2+2] Cycloaddition Reactions of Isocyanates and Thioisocyanates across the M=C Bond in a Ruthenium Carbene Complex

The reactivity of the (carbene)ruthenium complex [(?6-p-cymene)Ru=CRR?] with the unsymmetrical methandiide ligand [CRR?=C(Ph2PS)(SO2Ph)] towards different unsaturated organic substrates was examined. While no transformation was observed with a series of different ketones (no Wittig-type reactivity), treatment with isocyanates as well as thioisocyanates resulted in selective [2+2] cycloaddition reactions across the Ru=C double bond. The products were isolated in high yields and characterized in solution as well as in the solid state. The addition reactions were found to proceed selectively according to the HSAB principle with the soft ruthenium center preferring the softer donor atoms. Hence, isocyanate addition occurred with the C=N bond, while the thioisocyanates added to the metal–carbon bond with the C=S bond. Density functional theory studies on the reaction mechanism confirmed the observed selectivity and the formed complexes as kinetically as well as thermodynamically favoured products. Selective [2+2] cycloaddition reactions of heteroallenes across the M=C bond in a ruthenium carbene complex were achieved. The reactions occurred selectively according to the HSAB principle with the soft ruthenium center preferring the softer donor atom of the heteroallene.

Posted on 12 August 2015 | 10:20 am

Hierarchical Fe3O4 Core–Shell Layered Double Hydroxide Composites as Magnetic Adsorbents for Anionic Dye Removal from Wastewater

Hierarchical core–shell Fe3O4@Mg3Al–CO3 layered double hydroxide (LDH) as an efficient magnetic adsorbent was prepared and investigated for the adsorption of anionic dye under ambient conditions. The material was thoroughly characterized by a variety of spectroscopic methods, which indicate that it was composed of spherical Fe3O4 (ca. 330 nm) core with a vertically aligned Mg3Al-CO3 layered double hydroxide shell coating. Calcination of Fe3O4@Mg3Al–CO3 LDH at 400 °C gives a layered double oxide coated Fe3O4 nanoparticles (Fe3O4@Mg3Al–CO3 CLDH), which is shown to be an efficient magnetic adsorbent for removal of the anionic dye, C.I. Acid Yellow 219 (AY219) from aqueous solution under ambient conditions. The adsorption of AY219 from aqueous solution utilizes the “memory effect” of LDHs by which the calcined LDH can be reconstructed by intercalation of AY219 in water. During the multi-cycling tests, a stable adsorption capacity of 1024 mg/g was achieved after 3 cycles, which is the highest value among all reported magnetic dye adsorbents. We also demonstrate that the core-shell structure played a great role for the superior performance of Fe3O4@Mg3Al–CO3 CLDH, as its performance was much better than a control hybrid mixed phase Fe3O4/Mg3Al–CO3 LDH. This research suggests that Fe3O4@Mg3Al–CO3 LDH adsorbent is a promising candidate for the treatment of wastewater contaminated by anionic dyes. A hierarchical core-shell Fe3O4@layered double hydroxide composite consisting of a Fe3O4 core and a vertically aligned LDH shell was prepared as magnetic adsorbent for the removal of anionic dye. A record adsorption capacity of 1024 mg/g was achieved even during multi-cycles, suggesting that this novel adsorbent is promising for the treatment of wastewater contaminated by anionic dyes.

Posted on 11 August 2015 | 12:40 pm

Doped Framework Iron Hydroxyl Phosphate as Photocatalyst for Hydrogen Production from Water/Methanol Mixtures

In the search for novel photocatalysts for hydrogen production and with the ?-Fe2O3 photoelectrocatalyst as a recent precedent, we report herein the preparation, semiconductor properties and photocatalytic activity of metal-doped (0.1–5 wt.-% loading) iron hydroxyl phosphate (FeP). X-ray diffraction analyses of FeP samples subjected to extended photocatalytic irradiation showed the stability of this framework phosphate under photocatalytic conditions. Doping increased the photocatalytic efficiency of FeP for all dopants, with the optimal doping level between 0.1 and 1?%. Under the optimized conditions (Cr at 1?% doping), the photocatalytic activity of FeP reached a hydrogen production rate of 35.82 ?mol?gFe–1 in the absence of platinum as co-catalyst. The conduction flat band potential was estimated by photocurrent measurements or impedance spectroscopy to be 0.1 eV versus NHE and the charge carrier density 2.6?×?1020 carriers?cm–3. Transient absorption spectroscopy revealed a transient species decaying on the microsecond timescale characterized by a broad band spanning 300–750 nm. This transient was attributed to the charge-separated state. These results are promising for the development of novel photocatalytic materials based on framework metal phosphate. Open-framework iron hydroxyl phosphate can be easily doped and exhibits semiconductor behaviour under visible light leading to hydrogen generation

Posted on 11 August 2015 | 12:40 pm

Chemical Aspects of the Generation, Trapping, and Decay of Atomic Hydrogen in AlF3 and CaF2

Hydrogen atoms were generated in the matrices AlF3 and CaF2 at room temperature by ionizing radiation (? and UV) and were investigated by electron paramagnetic resonance spectroscopy. To gain information on the nature of the hydrogen precursors and hydrogen traps within the solid matrices, studies regarding defined thermal and chemical influence, as well as mechanical impact on the fluoridic matrices before and after irradiation were the focus of this work. Impurities such as HO– and hydrocarbons were identified as potential precursors. The hydrogen traps were characterized by means of their spatial distribution within the different samples and by their energetic states (“trap-depth”). In this respect, the rate constants, which were determined for different temperatures, turned out to be a valuable tool. Similarities and differences regarding the generation and stabilization of atomic hydrogen in AlF3 and CaF2 were worked out. Also, the influence of the type of ionizing radiation was elucidated. Whereas the comparison of AlF3 and CaF2 was dominated by similarities, significant differences were found for rather molecular siloxane cages R8Si8O12, especially regarding their reaction upon UV excitation and the possibility to resolve super-hyperfine splittings. It is well known that hydrogen atoms can be generated in the matrices AlF3 and CaF2 at room temperature by ionizing radiation. To learn more about the nature of the hydrogen precursors and hydrogen traps, electron paramagnetic resonance spectroscopy studies regarding defined thermal and chemical influence, as well as mechanical impact on the fluoridic matrices before and after irradiation are performed.

Posted on 11 August 2015 | 12:40 pm

Linking Flavonoids to Gold – A New Family of Gold Compounds for Potential Therapeutic Applications

The flavone ligands 8-chloro-2-tetrahydrofuryl-1,4-benzopyrone and 8-chloro-2-(2-methyltetrahydrofuryl)-1,4-benzopyrone have been used to prepare the first examples of alkynyl phosphine gold compounds containing flavonoids which exhibit cytotoxicity towards human prostate cancer cells. The first examples of alkynyl phosphine gold compounds containing flavonoids have been synthesized. They exhibit cytotoxicity towards human prostate cancer cells.

Posted on 11 August 2015 | 12:40 pm

Synthesis, Characterization, and Biological Properties of Osmium-Based Tamoxifen Derivatives – Comparison with Their Homologues in the Iron and Ruthenium Series

Three osmium analogues 3a–3c of hydroxytamoxifen were prepared. The antiproliferative effects of these complexes were measured against two breast cancer cell lines (MCF-7 and MDA-MB-231) and compared with those of their homologues of ferrocene (1a–1c) and ruthenocene (2a–2c). The tamoxifen-like complexes 2c and 3c derived from osmium and ruthenium show good cytotoxicities against the two cell lines (IC50 values between 2 and 3 ?M), albeit lower than those of ferrocifen 1c (IC50 between 0.5 and 0.8 ?M). These complexes induce senescence of the cells at low concentration (0.5 ?M). The mono- and diphenol complexes of osmium and ruthenium show little cytotoxicity against the two cell lines (2a, 2b, 3a, 3b; IC50 ? 30 ?M), whereas the iron analogues show high cytotoxicity (1a and 1b; IC50 = 0.6–1.1 ?M against MDA-MB-231). Further studies show that the cytotoxicity of the tamoxifen-like complexes of ruthenium and osmium is multifactorial and is partly due to the presence of the amino chain. Added to this is an effect of the metal center that could be due to a difference in the rate of formation, solubility, and stability of the corresponding quinone methides or to a difference in the acidity of the phenol protons. This work reveals the differences in the mechanisms of action that exist among the complexes of these three metallocenes. The uniqueness of the ferrocene complexes is underlined, but the cytotoxicity of the tamoxifen-like complexes of osmium and ruthenium is also demonstrated. The antiproliferative activities of newly synthesized osmium complexes are compared with those of their homologues in the iron and ruthenium series. All of the tamoxifen-like derivatives exhibit low IC50 values, whereas the Ru and Os diphenols are only slightly cytotoxic.

Posted on 11 August 2015 | 12:40 pm

Synergistic and Antagonistic Ligand Effects in the Transformation of Silver Compounds of Keto- and Cyano-Functionalised Oximates and Nitronates: A Systematic Study Using Thermal Analysis

Molecular silver compounds are target precursor molecules for the deposition of silver films from solution. The thermal decomposition of silver complexes of nitro and nitroso derivatives of malononitrile, cyanoacetamide and methyl cyanoacetate as well as with nitroacetamide and methyl nitroacetate was investigated for the first time in a systematic manner. The analysis of the evolving gases by means of infrared spectroscopy or mass spectrometry revealed that intramolecular redox reactions had a significant impact on the reaction mechanism, in particular the interactions of the nitro and nitroso functionalities with amido and ester groups. The studied ligands bearing cyano groups typically lead to the intermediary formation of silver cyanide, whereby metallic silver is formed only at higher temperatures. Silver complexes of nitroacetamide and methyl nitroacetate, however, undergo decomposition to metallic silver at temperatures already below 200 °C. Thin films of silver on glass substrates could be synthesised by spincoating of these precursors and subsequent annealing. Higher conversion temperatures lead to more uniform surface coverage and lower film roughness. The thermal decomposition of silver compounds with functionalised oximato and nitronato ligands proceeds by intra- and intermolecular redox reactions and can also involve unexpected rearrangements. The quest for suitable molecular precursors by variation of side groups within the ligands is a delicate matter, but can be facilitated by advanced thermal analysis. The correct combination of moieties can achieve decomposition at low temperatures.

Posted on 10 August 2015 | 12:50 pm

Cytotoxicity and Structural Analyses of 2,2?-Bipyridine-, 4,4?-Dimethyl-2,2?-bipyr­idine- and 2-(2?-Pyridyl)quinoxalineplatinum(II) Complexes

Platinum anticancer complexes incorporating 2,2?-bipyridine (bpy), 4,4?-dimethyl-2,2?-bipyridine (44Me2bpy) or 2-(2?-pyridyl)quinoxaline (2pq) as polyaromatic ligands and the S,S or R,R isomer of 1,2-diaminocyclohexane as ancillary ligands in the form [Pt(PL)(AL)]2+ have been synthesised and characterised. X-ray diffraction was used to elucidate the structure and stacking behaviour of the complexes, revealing interesting properties that may impact their biological activity. Pulsed gradient spin-echo NMR experiments elucidated the aggregation behaviour of these complexes in solution. The cytotoxicity of each complex was assessed against the L1210 murine leukaemia, HT29 human colon carcinoma and U87 human glioblastoma cell lines and compared to other complexes within this class. The complexes incorporating 44Me2bpy were found to be the most potent at inhibiting cell growth with IC50 values for the S,S isomer (0.13–0.5 ?M) less than that for cisplatin (0.36–11 ?M), oxaliplatin (0.9–1.8 ?M) or carboplatin (>50 ?M). Most complexes were found to be very effective against HT29 colon carcinoma cells. Structurally distorted platinum complexes incorporating bpy, 44Me2bpy, and 2pq were synthesised. X-ray crystallography of five complexes showed unexpected coordination geometry that could impact biological activity and aggregation. PGSE NMR studies supplement these findings. Cytotoxicity was assessed against three cell lines, revealing unexpected trends between complexes and potent overall activity in the HT29 line.

Posted on 7 August 2015 | 12:10 pm

Luminescence and Relaxometric Properties of Heteropolymetallic Metallostar Complexes with Selectively Incorporated Lanthanide(III) Ions

The synthesis and characterization of two diethylenetriaminepentaacetic acid (DTPA) based heteropolymetallic metallostar lanthanide complexes with the general formulas (GdL1)3Ln and (GdL2)3Ln are described. The synthesis uses a synthetic approach recently developed in our group for the selective complexation of gadolinium(III) and luminescent lanthanide ions with a ditopic ligand to form highly paramagnetic and luminescent metallostar complexes. The luminescence data and relaxometric studies suggest the potential applicability of the complexes as bimodal contrast agents for magnetic resonance and optical imaging. Owing to the higher excited state of L1, better sensitization was observed for all (GdL1)3Ln complexes than for (GdL2)3Ln. A large increase of the quantum yield from 1.5 to 9.8?% was observed for the (GdL1)3Eu complex compared with (GdL2)3Eu, whereas the (GdL1)3Tb complex exhibited a quantum yield (QY) of 30.9?% compared with 15.3?% for (GdL2)3Tb. A slight increase of the QY from 0.8 to 1.2?% was observed for the Dy(III) complex when switching from ligand L2 to L1. The nuclear magnetic relaxation dispersion (NMRD) measurements of the (GdL2)3Ln complexes (Ln = EuIII, DyIII, TbIII) showed respective longitudinal relaxivity (r1) values of 24.27, 22.80 and 21.72 s–1?mmol–1 per metallostar complex at 310 K and 20 MHz. The selective incorporation of gadolinium(III) and luminescent lanthanide ions into ditopic ligands results in highly paramagnetic and luminescent metallostar complexes with potential use as probes for bimodal contrast agents for magnet resonance imaging (MRI) and optical imaging.

Posted on 7 August 2015 | 12:10 pm

Synthesis, Characterization, and Reactivity of Functionalized Trinuclear Iron–Sulfur Clusters – A New Class of Bioinspired Hydrogenase Models

The air- and moisture-stable iron–sulfur carbonyl clusters Fe3S2(CO)7(dppm) (1) and Fe3S2(CO)7(dppf) (2) carrying the bisphosphine ligands bis(diphenylphosphanyl)methane (dppm) and 1,1?-bis(diphenylphosphanyl)ferrocene (dppf) were prepared and fully characterized. Two alternative synthetic routes based on different thionation reactions of triiron dodecacarbonyl were tested. The molecular structures of the methylene-bridged compound 1 and the ferrocene-functionalized derivative 2 were determined by single-crystal X-ray diffraction. The catalytic reactivity of the trinuclear iron–sulfur cluster core for proton reduction in solution at low overpotential was demonstrated. These deeply colored bisphosphine-bridged sulfur-capped iron carbonyl systems are discussed as promising candidates for the development of new bioinspired model compounds of iron-based hydrogenases. Trinuclear bisphosphine-bridged iron carbonyl clusters are introduced as homogeneous catalysts for proton reduction. Hydrido species form in the presence of acids, and hydrogen is produced electrocatalytically at low overpotential. These electron-rich iron–sulfur clusters are discussed as a promising starting point for the development of photochemical model compounds of iron-based hydrogenases.

Posted on 7 August 2015 | 12:10 pm

Synthesis of Silica@Ni-Co Mixed Metal Oxide Core–Shell Nanorattles and Their Potential Use as Effective Adsorbents for Waste Water Treatment

SiO2@Ni-Co mixed metal oxide core–shell nanorattles with different Ni2+/Co2+ molar ratios have been successfully synthesized through a facile, inexpensive self-template route by the calcination of SiO2@Ni-Co layered double hydroxides at 500 °C. The formation of SiO2@Ni-Co mixed metal oxide core–shell nanorattles has been confirmed by an array of characterization techniques. Field-emission scanning electron microscopy (FE-SEM) analysis indicates a hierarchical flowerlike morphology for the SiO2@Ni-Co mixed metal oxide core–shell nanorattles, and transmission electron microscopy (TEM) analysis confirms the formation of core–shell nanorattles. The diffuse reflectance spectra of the SiO2@Ni-Co mixed metal oxide core–shell nanorattles show two band-gap absorptions attributed to metal-to-ligand charge-transfer transitions (Mn+O2–). The SiO2@Ni-Co mixed metal oxide core–shell nanorattles have been explored as effective adsorbents for the removal of rhodamine B, methylene blue, and their mixture from aqueous solutions. The adsorption of the single dye systems follows Langmuir and Freundlich isotherms, whereas a binary Langmuir model has been applied for the binary dye systems. The SiO2@Ni-Co mixed metal oxide core–shell nanorattles possess higher adsorption capacity for the individual dyes than for the mixture of dyes. Kinetic studies indicate that the adsorptions of rhodamine B, methylene blue, and their mixture follow pseudo-second-order kinetics. SiO2@Ni-Co mixed metal oxide core–shell nanorattles are synthesized by the calcination of SiO2@Ni-Co layered double hydroxides at 500 °C. The nanorattles are explored as effective adsorbents for the removal of mixtures of rhodamine B and methylene blue from an aqueous solution. The nanorattles exhibit better adsorption capacity than the individual metal oxides.

Posted on 7 August 2015 | 12:10 pm

Hexaethyl-2,3,5-tricarba-nido-hexaborane(7), Its Monoanion and the (Triphenylphosphane)gold and Dicarbonylrhodium Complexes

Experimental and calculated [B3LYP/6-311+G(d,p) level of theory] NMR parameters [chemical shifts ?11B and ?13C, and coupling constants 1J(13C,11B) and 1J(11B,11B)] of hexaethyl-2,4-dicarba-nido-hexaborane(8), hexaethyl-2,3,5-tricarba-nido-hexaborane(7) and their monoanions are reported. The solid-state structure of the 2,3,5-tricarbaborane was determined by X-ray crystallography as the Au–PPh3 complex, where the gold atom is linked to C5 (88?%) with contacts to B4,6 or to C2,3 (12?%) with contacts to B4,6. The 2,3,5-tricarbaborate anion ?5-coordinates to the Rh(CO)2 fragment, forming a closo cluster. The gold complex obtained from the nido-carbaborate anion and in which the AuPPh3 fragment replaces isolobally an endo hydrogen atom, exists with Au–B4C5B6 coordination in solution, whereas in the solid state a second isomer with Au–B4C3C2B6 coordination is also present.

Posted on 6 August 2015 | 12:20 pm

Non-Condensed (Oxo)Nitridosilicates: La3­[SiN4]F and the Polymorph o-La3­[SiN3O]O

The isotypic compounds La3[SiN4]F and La3[SiN3O]O were synthesized in a radio-frequency furnace at 1600 °C. The crystal structures [Pnma (no. 62), Z = 4; La3(SiN4)F: a = 9.970(3), b = 7.697(2), c = 6.897(2) Å, V = 529.3(3) Å3; La3(SiON3)O: a = 9.950(2), b = 7.6160(15), c = 6.9080(14) Å, V = 523.48(18) Å3] were elucidated from single-crystal X-ray diffraction data and corroborated by Rietveld refinement, lattice-energy calculations (Madelung part of lattice energy, MAPLE) and Raman/FTIR spectroscopy. Both compounds are homeotypic with Na2Pr[GeO4]OH forming a network of vertex-sharing FLa6/OLa6 octahedra, whose voids are filled with non-condensed SiN4/SiN3O tetrahedra. o-La3[SiON3]O is the orthorhombic polymorph of this compound, which probably represents the high-temperasture modification, whereas the tetragonal polymorph t-La3[SiON3]O represents the low-temperature modification. While the space group of the t-polymorph [I4/mcm (no. 140)] differs from the new La3[SiN4]F and o-La3[SiN3O]O, the crystal structure contains the same linking pattern. La3[SiN4]F and o-La3[SiN3O]O represent new ortho-(oxo)nitridosilicates and were synthesized by the use of reactive starting materials. The crystal structures were solved and refined in an orthorhombic space group based on single-crystal X-ray data. A representative structural feature of both compounds are non-condensed SiN4/SiN3O tetrahedra.

Posted on 6 August 2015 | 12:20 pm

The Catalytic Role of Extra Molecules in the Aminolysis or Heterolytic Cleavage of an Iridium Alkoxycarbene Complex

A theoretical analysis was performed on reactions involving iridium alkoxycarbene complex [IrCp*Cl{=C(OCH3)CHCPh2}(PPh2Me)]PF6 (Cp* = pentamethylcyclopentadienyl), which can undergo aminolysis or heterolytic cleavage of the carbon(sp3)–oxygen bond. The energy barriers of these pathways were estimated and the reasons for the reactivity of the system evaluated. Aminolysis or heterolytic cleavage of the carbon(sp3)–oxygen bond is the result of a subtle equilibrium between electronic, steric, and cooperative effects. Cooperative effects facilitate the proton transfer that occurs in aminolysis through formation of a bridge by one or several molecules. These molecules act as catalysts that decrease the energy barrier and change the favored pathway, so that the environment is a key factor in the reactivity of this complex. A theoretical study on reactions of iridium alkoxycarbene complex [IrCp*Cl{=C(OCH3)CHCPh2}(PPh2Me)]PF6, which can undergo aminolysis or heterolytic carbon(sp3)–oxygen bond cleavage, was performed. Cooperative effects facilitate the proton transfer that occurs in aminolysis by formation of a bridge by one or several molecules, which decreases the energy barrier and changes the favored pathway.

Posted on 6 August 2015 | 12:20 pm

Synthesis of Rod-Like g-C3N4/ZnS Composites with Superior Photocatalytic Activity for the Degradation of Methyl Orange

A rod-like g-C3N4/ZnS composite was synthesized via a hydrothermal process using g-C3N4, Zn(NO3)2·6H2O, thioglycolic acid, and thioacetamide as precursors under reflux conditions. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV/Vis absorption spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, inductively coupled plasma (ICP) spectroscopy, and photoluminescence (PL) spectroscopy. The amount of g-C3N4 was systematically varied, and it was found that the g-C3N4 content not only plays an important role in the formation of g-C3N4/ZnS rod-like composites but also the improvement of the photocurrent response. The photocatalytic experimental results indicated that the 10 wt.-% g-C3N4/ZnS nanocomposite enhances photocatalytic performance with 93.0?% decomposition of methyl orange (MO) after 100 min under simulated sunlight irradiation. This new composite is expected to show considerable potential in the treatment of wastewater containing organic pollutants. Photogenerated electron-hole pairs were produced by ZnS under simulated sunlight irradiation. The photogenerated holes on ZnS easily transfer electrons to g-C3N4, which is beneficial in degrading pollutants.

Posted on 6 August 2015 | 12:20 pm

TeO2 Nanoparticle Loaded Graphitic Carbon Nitride Hybrids: Their Preparation and Catalytic Activities in the Thermal Decomposition of Ammonium Perchlorate

TeO2 nanoparticle-loaded graphitic carbon nitride hybrids (TeO2NPs/g-C3N4) were successfully prepared by a calcination strategy. Various characterization and detection techniques were used to analyze its structure and properties. It was found that upon the addition of 10 wt.-% of the as-prepared hybrids, the onset decomposition temperature of ammonium perchlorate (AP) decreased by 104.4 °C. In addition, the addition of TeO2 NPs resulted in an increase in the surface area up to 8.8 m2?g–1 for g-C3N4, which is three times larger than that of the bulk g-C3N4 (2.8 m2?g–1). Furthermore, g-C3N4 reacted with HClO4 by Lewis acid–base interaction, which resulted in separation of HClO4 from AP lattice. Notably, the separation of the HClO4 gas molecule led to continued decomposition of AP, as this decomposition reaction is reversible. With this in mind, a catalytic mechanism based on Lewis acid–base interaction was proposed to illustrate the catalytic process in the thermal decomposition of AP. The high-temperature thermal decomposition (HTD) of ammonium perchlorate (AP) is decreased by 104.4 °C if the TeO2 nanoparticle/graphitic carbon nitride (g-C3N4) hybrids are added to AP. Furthermore, a Lewis acid–base interaction catalytic mechanism is proposed to illustrate the thermal decomposition of AP; CB = conduction band, VB = valence band, h+ = hole, LTD = low-temperature thermal decomposition.

Posted on 6 August 2015 | 12:10 pm

Synthesis and Structures of N-Heterocyclic Carbene–Sulfonate Ruthenium Complexes and Their Applications in the Ring-Opening Metathesis Polymerization of Norbornene

A series of N-heterocyclic carbene–sulfonate (NHC–sulfonate) p-cymene ruthenium complexes (2a–2d) were synthesized in high yields from the reactions of NHC–sulfonate ligands with Ag2O and [(p-cymene)RuCl2]2. All of the complexes were characterized fully by 1H and 13C NMR spectroscopy, high-resolution mass spectrometry, and elemental analysis. The molecular structures of 2b and 2d were determined by single-crystal X-ray diffraction analysis. Upon activation with Et2AlCl, the ruthenium complexes 2a–2d showed excellent activities for the ring-opening metathesis polymerization of norbornene and produced polymers with high molecular weights and narrow molecular weight distributions. Complex 2a can also efficiently catalyze the copolymerization of norbornene and cyclooctene. All of the obtained polymers were characterized by 1H and 13C NMR spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). A series of N-heterocyclic carbene–sulfonate ruthenium complexes are synthesized and applied for the ring-opening metathesis polymerization of norbornene and the copolymerization of norbornene and cyclooctene.

Posted on 6 August 2015 | 12:10 pm

S–S Bond Activation in Multi-Copper ­Aggregates Containing Perthiocarboxylato Ligands

The direct reaction between [Cu(OAc)2·(H2O)]2 and n-butyldithiocarboxylic acid affords two copper(I) aggregates with dithiocarboxylato, [Cu(S2C-n-butyl)]4 (1), and perthiocarboxylato ligands, [Cu(S3C-n-butyl)]4 (2), in which the oxidation of dithiocarboxylato ligand is triggered by the CuII centers. The activation of the S–S bond in 2 by two reducing agents, PPh3 and NaBH4, has been investigated both experimentally and by DFT calculations. The successive S–S activation in 2 by reaction with 4 equiv. of PPh3 is a cooperative process, which implies that the intermediate species remain elusive. Such intermediates have been analyzed by DFT calculations, which established that the reactivity of the multi-copper structures depends on the balance between the interactions in the different coordination spheres imposed on the copper centers and the Cu···Cu distances. Furthermore, weak cuprophilic interactions are conditioned by the orbital orientation imposed by the structure. This implies that these metal–metal interactions are not always found between the pairs of Cu atoms with the shortest distances. Although different products have been isolated depending on the reducing agent, the overall theoretical data indicate that the reagent always attacks the terminal sulfur atom of the perthio group. As a consequence of S–S activation in [Cu4(?-S3C-n-butyl)4], a complex reactivity is triggered in which both Cu–S coordination versatility and subtle Cu···Cu interactions play distinct key roles.

Posted on 3 August 2015 | 11:50 am

Photoluminescence Modulation in Lan­thanide(III)/Pyrazine-2,5-dicarboxylato/Nitrato Frameworks

The solvent-free melt reactions between lanthanide(III) nitrates and pyrazine-2,5-dicarboxylic acid (H2pzdc) gave rise to four families of 3D compounds that differ from those accessible from conventional solvothermal synthesis, namely, {[Ln(?4-pzdc)(NO3)(H2O)2]·2.33H2O}n (1-Ln; Ln = La, Ce), {[Ln9(?4-pzdc)9(NO3)2(H2O)25](NO3)7·8H2O}n (2-Ln; Ln = Pr, Nd), {[Ln6(?4-pzdc)5(?3-pzdc)2(?-pzdc)(H2O)10](NO3)2·2H2O}n (3-Ln; Ln = Nd, Sm), and [Ln(?4-pzdc)(NO3)(H2O)]n (4-Ln; Ln = Eu, Gd, Tb). This synthetic approach promotes the incorporation of nitrate anions into the final crystal structure as terminal ligands or counterions, which replace water molecules in the coordination sphere and enhance the photoluminescence properties of these compounds. The neodymium, samarium, europium, and terbium compounds exhibit their characteristic emissions in the infrared and visible regions. The pzdc ligand shows the highest sensitization towards TbIII ions, and the photoluminescence intensity can be modulated by immersing the sample into different solvents and also by dehydrating it. Compounds 3-Ln have a topology named as jcr5, which has not been reported previously. Four types of 3D LnIII/pyrazine-2,5-dicarboxylato/nitrato frameworks are synthesized through a solvent-free approach. Their structural diversity is rationalized according to the lanthanide contraction effect and the role played by the nitrate ion (ligand or counterion). The photoluminescence of the complexes can be tuned in response to thermal dehydration.

Posted on 3 August 2015 | 11:50 am

Carrageenan–Silica Hybrid Nanoparticles Prepared by a Non-Emulsion Method

Spherical and monodispersed sub-micrometer sized particles of organic–inorganic hybrids were prepared by means of a sol–gel non-emulsion method using the biopolymer ?-carrageenan and the alkoxysilane 3-isocyanatopropyltriethoxysilane (ICPTES). The structural characterization of the carrageenan–silica hybrid particles was performed by using FTIR spectroscopy and solid-state 29Si and 13C NMR spectroscopy and confirmed that ?-carrageenan was covalently linked to the siliceous network via urethane bonds. Zeta-potential measurements indicate the hybrids were functionalized on the surface with sulfonate groups from the polysaccharide. These hybrids display thermal sensitivity, which is of great relevance for biomedical applications such as drug encapsulation and thermally controlled drug-delivery systems. Nanoparticles of ?-carrageenan–silica hybrids with narrow size distribution were prepared by using a sol–gel non-emulsion method. Unlike silica particles, these hybrids display thermal sensitivity, which is of great relevance for biomedical applications such as drug encapsulation and thermally controlled drug-delivery systems.

Posted on 3 August 2015 | 11:50 am

Photoinduced DNA Crosslink Formation by Dichloridooxidovanadium(IV) Complexes of Polypyridyl Bases

Oxidovanadium(IV) complexes [VO(pyphen)Cl2] (1) and [VO(pydppz)Cl2] (2), where pyphen is 2-(2?-pyridyl)-1,10-phenanthroline and pydppz is 3-(pyridin-2-yl)dipyrido[3,2-a:2?,3?-c]phenazine, show remarkable photoinduced DNA crosslinking ability and photocytotoxicity. The complexes are non-electrolytes in DMF, 1:1 electrolytes in 20?% aqueous DMF, and 1:2 electrolytes in 20?% aqueous DMF upon photoirradiation with visible light of 400–700 nm. The paramagnetic complexes, which have one unpaired electron, show a d–d band near 780 nm in aqueous DMF. The IR data suggest a V=O moiety trans to a V–N bond. Complex [VO(pydppz)Cl2] (2), as a novel photoinducible nuclear ds-DNA crosslinking agent, shows visible-light-induced cytotoxicity in HeLa and MCF-7 cancer cells by an apoptotic pathway, giving IC50 values of 0.87?±?0.07 and 1.4?±?0.2 ?M, respectively, while being essentially nontoxic (IC50 > 40 ?M) in the dark and less toxic in normal MCF-10A cells. Oxidovanadium(IV) complexes of polypyridyl bases having two dissociable chloride ligands show DNA crosslink formation involving nuclear DNA in a buffer medium upon photoirradiation with visible light of 400–700 nm. The complexes are remarkably photocytotoxic in cancer cells while being essentially nontoxic in the dark.

Posted on 30 July 2015 | 11:20 am

Trimetallic PEPPSI-Type Palladium N-Heterocyclic Carbene Complexes – Improved Catalyst Lifetime in the Mizoroki–Heck Coupling Reaction

A series of mono- and dendritic trimetallic PEPPSI-type (pyridine-enhanced precatalyst preparation stabilization and initiation) complexes bearing N-heterocyclic carbene (NHC) ligands containing a protected amine in the form of an ethylphthalimido group have been synthesized. These discrete prototypes of complexes covalently bound to suitable supports have been studied in the Mizoroki–Heck coupling of aryl iodides under mild conditions, including sets of experiments to assess the lifetime of the active species. The palladated dendrons are more efficient and robust catalysts than their monometallic counterparts. Dendritic trimetallic PEPPSI-type (pyridine-enhanced precatalyst preparation stabilization and initiation) complexes are more efficient and robust catalysts than their monometallic counterparts in the Mizoroki–Heck coupling of aryl iodides under mild conditions.

Posted on 30 July 2015 | 11:20 am

Borosulfates Cs2B2S3O13, Rb4B2S4O17, and A3HB4S2O14 (A = Rb, Cs) – Crystalline Approximants for Vitreous B2O3?

New borosulfates were obtained by reaction of B2O3 in oleum or concentrated H2SO4 at temperatures between 300 and 360 °C. They are the first examples of borosulfates with directly connected boron polyhedra, that is, ditetrahedral B2O7 or layers of trigonal-planar BO3 units. Cs2B2S3O13 [P21/c, Z = 4, a = 14.765(3), b = 6.710(1), c = 12.528(3) Å, ? = 104.60(3)°] contains layers of corner-sharing BO4 and SO4 tetrahedra. The BO4 tetrahedra form dimers. SO4 tetrahedra connect four B2O7 dimers to rings containing 10 tetrahedra, which are condensed to a layer. A third SO4 tetrahedron connects two BO4 tetrahedra of the B2O7 unit. The layers are stacked in the [100] direction. One Cs+ cation is located within the layer of tetrahedra, the second one between the layers. In Rb4B2S4O17 or Rb4[B2O(SO4)4] [Pnna, Z = 4, a = 8.0415(9), b = 10.6466(11), c = 20.425(2) Å], there are isolated [B2O(SO4)4] units which consist of a central B2O7 unit. Besides one B–O–B bridge, two SO4 tetrahedra connect the BO4 tetrahedra. Additionally, each BO4 tetrahedron has a terminal SO4 unit. In the structure of A3HB4S2O14 or A3H(SO4)2(B2O3)2 [P63/m, Z = 2, A = Cs: a = 6.5648(2), c = 19.5669(5) Å; A = Rb: a = 6.502(6), c = 19.023(14) Å], the SO4 tetrahedra are isolated. Boron forms planar layers of corner-sharing trigonal-planar BO3 units. There are two different types of BO3 units in a ratio of 3:1. The first type forms six-membered boroxol rings, B3O3, which are connected to the layers by the second type of BO3 units. The layers are separated by isolated SO42– tetrahedra and Cs+ cations. The “missing” proton could not be localized but was assumed to achieve electroneutrality and was confirmed by IR spectroscopy. Planar layers of B2O3 with trigonal-planar BO3 units and boroxol rings are supposed to exist as structure elements in vitreous boron oxide. Cs2B2S3O13 and Rb4B2S4O17 are the first examples of borosulfates with directly connected BO4 tetrahedra. Similar motifs are known for borates and borosulfates. In A3HB4S2O14 (A = Rb, Cs) there are planar layers of B2O3 with trigonal BO3 units and boroxol rings B3O3. These are the characteristic features of vitreous B2O3.

Posted on 30 July 2015 | 11:20 am

Copper(II) Cyclam Complexes with N-­Propionic Acid Pendant Arms

Four cyclam (1,4,8,11-tetraazacyclotetradecane) ligands with different numbers of N-substituted propionic acid groups lead to pentacoordinate copper(II) complexes that adopt trans-I configurations (4+1 geometry), that is, the complexes have a d?x?2–y?2 ground state with significant rhombic distortion. From the structural data (X-ray diffraction analysis and electron paramagnetic resonance, UV/Vis and IR spectroscopy), as the number of secondary amine groups of the macrocyclic ring substituted with propionic acid groups increases, the distortion from square pyramidal to trigonal bipyramidal increases, and this is expected to lead to relatively low complex stabilities. This is confirmed by in vitro studies with superoxide dismutase (SOD) and human serum challenge experiments as well as by biodistribution data with the 64Cu-labelled complexes. The 64Cu-labelled complexes with cyclam monopropionic and dipropionic acid show high in vitro and in vivo stabilities, and the latter provides a comparable biodistribution profile to that of 64Cu–TETA (TETA = 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid). Four cyclam ligands with different numbers of N-propionic acid pendant arms were screened as potential bifunctional chelators for CuII radioisotopes. The pendant arms of the ligands strongly influence the stability of the CuII complexes formed. In this series, the cyclam ligands with one (HL1) and two N-propionic acid arms (H2L2) are promising ligands for radiopharmaceutical applications.

Posted on 27 July 2015 | 8:50 am

Experimental and Theoretical Investigations of CO2 Sorption by a 3D In-MOF with Multiple 1D Channels

The CO2 sorption capacity of the 3D In-MOF (Et2NH2)[In(2,6-NDC)2]·2H2O·DEF (I) (where 2,6-NDC is 2,6-naphthalenedicarboxylate and DEF is N,N-diethylformamide) was investigated. The solvent-free I contains three distinct types of 1D micropores with different shapes and pore dimensions. The evacuated I sorbed 297.2 cm3?g–1 (13.3 mmol?g–1) of CO2 at 196 K, 72.2 cm3?g–1 (3.22 mmol?g–1) at 273 K, and 39.8 cm3?g–1 (1.78 mmol?g–1) at 298 K. The difference between the uptake at 196 K and those at 273 and 298 K is relatively large. The shapes of the sorption isotherms are also dramatically different. At 196 K, the adsorption–desorption isotherms are S-shaped without significant hysteretic behavior between the adsorption and desorption branches. On the contrary, the adsorption isotherms measured at 273 and 298 K fit well with the Langmuir–Freundlich equation. The low-surface-coverage isosteric heat (Qst) of CO2 adsorption by I is 19.6 kJ?mol–1. Detailed estimations of the adsorption sites for CO2 were then performed by DFT calculations. The calculated binding energies were typically dependent on the dimension of the micropores when nonbonding (van der Waals) interactions were considered; the larger the micropore dimensions, the smaller the calculated binding energy. In addition, not only the framework CH···OCO contacts for Ch3 but also the counter-cation CH···OCO contacts for Ch1 and Ch2 were found to be important. The low-pressure CO2 sorption capacity of the 3D In-MOF (Et2NH2)[In(2,6-NDC)2]·2H2O·DEF (I) (where 2,6-NDC is 2,6-naphthalenedicarboxylate and DEF is N,N-diethylformamide) was investigated at various temperatures.

Posted on 24 July 2015 | 3:30 pm

Mechanisms of Oxygen Atom Transfer between Main-Group Elements

Oxygen atom transfer (OAT) between main-group elements is pivotal to a number of industrial processes such as the synthesis of thionyl chloride (SO3 + SCl2??SO2 + SOCl2) and sodium chlorate (3 NaOCl??NaClO3 + 2 NaCl), as well as the historic method of CO detection in mines via its reaction with I2O5 (I2O5 + 5 CO??I2 + 5 CO2). Surprisingly, little is known about the mechanisms of these and other OAT reactions involving main-group elements. Even the basic question as to whether such reactions are one-step, SN2-like displacements or multistep, involving oxo-bridged intermediates, remains largely unanswered. Extensive density functional theory calculations reported herein indicate a direct, SN2-like pathway as the norm for such processes. In the major quantum chemical study of oxygen atom transfer between main-group element centers, DFT calculations unequivocally indicate a one-step, SN2-like pathway as the normative mechanism, as opposed to a two-step associative-dissociative sequence that is common for transition metals.

Posted on 24 July 2015 | 3:30 pm

Orthogonal Functionalization of Ferritin via Supramolecular Re-Assembly

To investigate if the degree of functionalization of ferritin could be controlled using a supramolecular self-assembly process, two photophysical separable batches of ferritin were created by functionalizing ferritin capsids with either Cy3- or Cy5-dye (loading rate of about 50?%). After dis-assembly, Cy3-, Cy5- as well as non-functionalized ferritin subunits were mixed in variable ratios. Photophysical measurements revealed that the ratio in which the subunits were mixed was indeed indicative for the ratios in which the functionalized subunits were observed in the re-assembled capsids. During re-assembly, however, a slight preference for the inclusion of non-functionalized subunits was observed, indicating the reactivity decreased following functionalization. The iron biomineralization properties of ferritin were retained by the multi-functionalized capsids as FeII diffused rapidly inside making it visible by transmission electron microscopy (TEM). These combined data indicate that it is possible to functionalize ferritin in an orthogonal manner using the supramolecular interaction between ferritin subunits. To investigate the control on ferritin functionalization by supramolecular re-assembly, ferritin with modular functionality and still capable of iron mineralization was created. The ratio in which Cy3-, Cy5-, and non-functionalized subunits were mixed, was indicative for the ratio in which the variable subunits were observed in the re-assembled capsids.

Posted on 24 July 2015 | 3:20 pm

Synthesis and Characterization of GaIII, InIII and LuIII Complexes of a Set of dtpa Bis-Amide Ligands

The synthesis and characterization of five new diethylenetriaminepentaacetic acid (dtpa) ligands, (dtpa)-N,N?-bis(alkoxyphenylamide), and their complexation with GaIII, InIII and LuIII are reported. The procedures for the synthesis of all complexes in aqueous media are described as well as a synthetic pathway for the preparation of GaIII complexes in chloroform. All substances were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and HPLC. Single-crystal structure analysis was performed where applicable, which revealed the presence of hepta- and octa-coordinated isomers for InIII complexes and a nine-fold coordination of LuIII ions in the solid state. Additional NMR experiments suggested a hepta-coordinated InIII species in solution, whereas the GaIII complexes appear to be hexa-coordinated and the LuIII complexes to be octa-coordinated. Both NMR and HPLC studies indicated the presence of a single isomer in every complex. The synthesis and characterization of new GaIII, InIII and LuIII complexes of five dtpa bis-amides are described. As determined by single-crystal structure analysis, the InIII complexes are hepta- or octa-coordinated, whereas the LuIII are nona-coordinated in the solid state. NMR studies were undertaken to characterize the coordination behaviour of the complexes in solution.

Posted on 23 July 2015 | 2:20 pm

Cytocompatible Fluorescent Quantum Dot/PEG-Chitosan Bioconjugates for Nanomedicine Applications

In this study, novel nanobioconjugates based on quantum dots and a PEGylated chitosan derivative (PEG-CHI) have been designed and synthesised by a single-step aqueous route at room temperature. Chitosan was chemically modified by PEGylation aiming to significantly improve its water solubility and used as the capping ligand in the preparation of CdS quantum dot (QD) colloidal systems. UV/Vis and photoluminescence spectroscopy, transmission electron microscopy, dynamic light scattering, and the zeta potential were used to characterise the biopolymer-capped semi-conductor nanocrystals and their relative stability. The results clearly demonstrated that the PEG-CHI derivative is remarkably effective in nucleating and stabilising ultra-small colloidal CdS QDs in aqueous suspensions under acidic, neutral and alkaline media with an average size of approximately 2.0–3.0 nm and simultaneously showing luminescent activity in the visible range. In addition, the results of cell viability analysis in vitro using two cell cultures based on MTT bioassays demonstrated no cytotoxicity of the CdS QD/PEG-chitosan bioconjugates. Thus, based on these findings, it can be envisioned that these bioconjugates have potential use as biocompatible fluorescent biomarkers for nanomedicine applications. Novel nanobioconjugates based on Cd-based quantum dots and a PEGylated chitosan derivative as capping ligand have been designed and synthesised by a single-step aqueous route at room temperature. These nanohybrids are luminescent and cytocompatible towards two cell lines tested in vitro, therefore showing potential as biomarkers in nanomedicine applications.

Posted on 23 July 2015 | 2:20 pm

Recognition of Prochiral Sulfides in Five-Coordinate PtII Complexes

This article describes a stereochemical study on five-coordinate complexes of PtII containing a prochiral alkene (E-R1O2CCH=CHCO2R1) and a prochiral sulfide R2SR3, of general formula [PtMe(R2SR3)(dmphen) (E-R1O2CCH=CHCO2R1)]BF4. Through mono- and two-dimensional NMR spectroscopy, it was demonstrated that there is mutual recognition between the prochiral ligands in the presence of aryl sulfides R2SAr, whose origin was also explained. The equilibrium constants of sulfide exchange were also evaluated, which are in full agreement with the ?-donor properties of the ligands. A stereochemical study on five-coordinate complexes of PtII containing a prochiral alkene (E-R1O2CCH=CHCO2R1) and a prochiral sulfide R2SR3, of general formula [PtMe(R2SR3)(dmphen) (E-R1O2CCH=CHCO2R1)]BF4, has been described. It has been demonstrated that there is mutual recognition between the prochiral ligands in the presence of aryl sulfides R2SAr, whose origin has also been explained.

Posted on 23 July 2015 | 2:20 pm

One-Pot Synthesis of an Oxalato-Bridged CuII Coordination Polymer Containing an In Situ Produced Pyrazole Moiety: A Precursor for the Preparation of CuO Nano­structures

The synthesis, characterization, and thermal decomposition behaviour of the oxalato-bridged copper(II) coordination polymer [Cu2(C2O4)(L)2Cl2(MeOH)2]n (1) (L = 3,5-dimethyl-1H-pyrazole) is reported. Complex 1 is prepared in a straightforward fashion by a one-pot reaction of acetylacetone, thiosemicarbazide, oxalic acid and copper(II) chloride in a molar ratio of 2:2:1:2. Complex 1 was characterized by means of FT-IR spectroscopy, mass spectrometry and elemental analysis as well as single-crystal X-ray diffraction. Furthermore, the electrochemical behavior of 1 was investigated in DMSO by cyclic voltammetry. The thermal stability of complex 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Solventless thermolysis of complex 1 at 550 °C and 1000 °C under air afforded copper oxide nanoparticles and nanosheets, respectively. The CuO nanostructures were characterized by using a series of techniques including FT-IR, UV/Vis, XRD, XPS, EDAX, and SEM. The one-pot reaction of acetylacetone, thiosemicarbazide, oxalic acid and copper(II) chloride in a molar ratio of 2:2:1:2 affords coordination polymer [Cu2(C2O4)(L)2Cl2(MeOH)2]n (1) (L = 3,5-dimethyl-1H-pyrazole generated in situ). Thermolysis of complex 1 under neat conditions in air at 550 °C and 1000 °C generates CuO nanoparticles and nanosheets, respectively.

Posted on 23 July 2015 | 2:20 pm

Dioxygen Activation by an in situ Reduced CuII Hydrazone Complex

A CuII hydrazone complex has been synthesized that can be reduced in situ in boiling methanol to give the corresponding CuI complex. The latter complex readily activates dioxygen under ambient conditions, as was unambiguously shown by isotopic labeling studies. As a consequence of the dioxygen activation, the thienyl moiety appended to the hydrazone ligand is easily oxidized in ? position (C–H??C–O), finally leading to a change in the coordination environment of the central metal ion. All relevant complexes have been structurally characterized by single-crystal X-ray diffraction analyses. The hydrazone ligand applied in this study does not mimic a biologically relevant coordination motif in copper-containing oxygenases. Nonetheless, the reactivity of the CuI complex resembles that found in many oxygenases, indicating that hydrazone ligands may be well-suited for the generation of novel bioinspired oxidation catalysts. A CuII complex of a hydrazone ligand with N,N,S-donor functionality is reported that, after in situ reduction, is able to activate dioxygen, leading to a hydroxylation of the ligand and finally resulting in the formation of a CuII complex of a hydrazone ligand acting as an N,N,O-donor.

Posted on 20 July 2015 | 2:50 pm

Easily Vaporizable Ionic Liquids – No Contradiction!

It was a big surprise to see crystals of an ionic liquid (IL) forming by sublimation at room temperature. ILs are generally accepted to have negligible vapour pressures at elevated temperatures, making their sublimation or distillation very difficult. ILs that sublime easily contain silylimidazolium-based cations. In order to establish the details of the unusual behaviour of this subclass of ILs, a combined spectroscopic, X-ray crystallographic, physicochemical and theoretical characterization was performed. The results are compared with those of other easily vaporizable compounds, like ammonium chloride and naphthalene. The single-crystal X-ray structure analysis of one of these compounds, N-methyl-N?-dimethyl(phenyl)silylimidazolium chloride (monoclinic, C2/c), clearly shows the existence of isolated ions, demonstrating that the compound is an ionic liquid. Ionic liquids (ILs) are commonly known as compounds with negligible vapour pressure, which makes them difficult to boil/distil or sublime. Surprisingly, ILs with imidazolium-based cations with the specialty of N-bonded silylorganic groups sublime very easily. The process of sublimation has been investigated thoroughly with physicochemical methods and theoretical calculations.

Posted on 20 July 2015 | 2:50 pm

?-Excess ?2P=C–N–Heterocycles: Catalytic P-Arylation and Alkylation of N-Alkyl-1,3-benzazaphospholes and Isolation of P,N-Disubstituted Dihydrobenzaza­phosphole P-Oxides

2-Unsubstituted N-alkyl-1,3-benzazaphospholes, diagonally P–C related to 2,3-unsubstituted indoles, were successfully arylated by aryl iodides and bromides or alkylated by neopentyl iodide by heating in DMF in the presence of a catalytic amount of PdCl2 or H2PtCl6 and a suitable base. In contrast to the known 2-arylations of indoles under these conditions, the reactions led to arylation in the 3-position and proceeded via highly moisture-sensitive intermediates to P-substituted 1,3-benzazaphosphole P-oxides. Thus, we present a novel route for the direct P-substitution of aromatic ?2P-heterocycles with electrophilic aryl/alkyl halides. Characteristic NMR spectroscopic data of the intermediates are consistent with –P(aryl)–C(Br/Cl)–N– species formed by metal-mediated addition of the aryl halides at the P=C bond rather than by oxidative addition to ylidic intermediates. Benzazaphospholium salts, accessible by using triethyloxonium tetrafluoroborate at room temperature and also very sensitive to hydrolysis, display distinct NMR spectroscopic data. The structures of the products were elucidated by conclusive NMR spectroscopy and HRMS data and crystal-structure analysis. Minor amounts of a bis(arylation) product could likewise be identified by crystal-structure analysis. Aromatic ?2P-heterocycles are unreactive to aryl/alkyl halides. Heating in the presence of Pd or Pt catalysts and a suitable base, however, allows direct P-arylation or P-alkylation. The intermediate products are extremely moisture-sensitive and are transformed into phosphine oxides. Et3OBF4 provides benzazaphospholium salts without a catalyst, but these also tend to hydrolyze to phosphine oxides.

Posted on 17 July 2015 | 11:20 am

Water-Soluble Palladium(II) Sulfonated Thiosemicarbazone Complexes: Facile Synthesis and Preliminary Catalytic Studies in the Suzuki–Miyaura Cross-Coupling Reaction in Water

A series of mono- and binuclear sulfonated thiosemicarbazone PdII complexes have been synthesised and characterised using nuclear magnetic resonance spectroscopy, infrared spectroscopy, electrospray ionisation mass spectrometry and elemental analysis. The complexes display excellent water-solubility at room temperature and in addition, 1H and 31P{1H} NMR spectroscopic experiments reveal that the mononuclear complex 4 is very stable in water at 70 °C. Consequently, preliminary catalytic experiments show the water-soluble complexes to be efficient catalyst precursors in the Suzuki–Miyaura cross-coupling reaction in water. No evidence of homo-coupling was observed and the water-soluble complexes demonstrated versatility in coupling substrates containing various functional groups. Mono- and binuclear thiosemicarbazone complexes were synthesized and characterized. The mononuclear complexes are very stable in water and all the catalysts are active for the Suzuki–Miyaura cross-coupling reaction of various substrates. The mononuclear catalysts were more active than their binuclear analogues. Catalyst 4 could be recycled efficiently twice.

Posted on 17 July 2015 | 11:20 am

Key Considerations for Sensing FeII and FeIII in Aqueous Media

Recently Ghosh et al. reported on the fluorescent response of commercially available N-(2-aminoethyl)naphthalen-1-amine toward FeII, FeIII, and HgII (K. Ghosh, S. Rathi, P. Gupta, P. Vashisth, V. Pruthi, Eur. J. Inorg. Chem. 2015, 311). The authors conclude that metal binding to the diamine chelator leads to chelation-induced quenching; however, the experimental protocols are incompatible with the aqueous chemistry of FeIII, which precludes this interpretation of the data. Recently, Ghosh et al. reported on the fluorescent response of N-(2-aminoethyl)naphthalen-1-amine toward FeII, FeIII, and HgII (K. Ghosh, S. Rathi, P. Gupta, P. Vashisth, V. Pruthi, Eur. J. Inorg. Chem. 2015, 311), concluding that metal binding to the diamine chelator leads to chelation-induced quenching; however, the experimental protocols are incompatible with the aqueous chemistry of FeIII.

Posted on 17 July 2015 | 11:20 am

The Reaction of Terminal Phosphinidene Complexes [RP–W(CO)5] with Vinylbor­onic Acids: Cycloaddition vs. P–C Bond Formation

The reaction of terminal phosphinidene complexes [RP–W(CO)5] with vinylboronic acids is very sensitive to the presence or absence of solid K3PO4 in suspension in the reaction medium. The products are phosphirane complexes without the salt and secondary vinylphosphine complexes in the presence of the salt. This shift of the reaction pathway is explained by the formation of vinyborates in the presence of potassium phosphate. Terminal phosphinidene complexes react with vinylboronic acid to give the expected phosphirane complexes, but the addition of K3PO4 changes the course of the reaction, and secondary vinylphosphine complexes are obtained instead.

Posted on 14 July 2015 | 5:52 pm

Cobalt(I) and Nickel(II) Complexes of Bis(1,3-diphosphacyclobutadiene) Sandwich Anions

Complexes [(C4Me4)Co(CO)2{Co(P2C2tBu2)2}] (1, C4Me4 = tetramethylcyclobutadiene) and [CpNi{Co(P2C2tBu2)2}(PPh3)] (2, Cp = cyclopentadienyl) were synthesized by transmetalating [Tl(thf)2{Co(P2C2tBu2)2}] with [(C4Me4)Co(CO)2I] and [CpNiBr(PPh3)]. Compounds 1 and 2 were fully characterized by X-ray crystallography, multinuclear NMR, UV/Vis, and IR spectroscopy, and elemental analysis. Their molecular structures show ?-coordination of one phosphorus atom of the [Co(P2C2tBu2)2]– anion to the second metal atom (cobalt or nickel). Time-dependent density functional theory (TD-DFT) calculations were applied to gain insight into the electronic structures and the nature of the electronic transitions observed in the UV/Vis spectra. Cyclic voltammetry studies revealed the similar redox behavior of 1 and 2, which are reversibly oxidized to the corresponding monocations 1+ and 2+ with retention of the dinuclear structures. The cyclic voltammograms furthermore show that 1 and 2 decompose upon reduction with cleavage of the dinuclear structures into the free [Co(P2C2tBu2)2]– anion and further uncharacterized products. Dinuclear diphosphacyclobutadiene complexes have been synthesized by transmetalating the thallium(I) salt [Tl(thf)2{Co(P2C2tBu2)2}] with organometallic cobalt(I) and nickel(II) halides. The structural, spectroscopic, and redox properties of two new bimetallic complexes are presented, and their electronic structures are analyzed by DFT calculations.

Posted on 14 July 2015 | 5:52 pm

Understanding and Tuning Bioinorganic Interfaces for the Design of Bionanocomposites

Interactions between biological molecules and inorganic species are of tremendous importance in nature. Attempts to create bionanocomposites associating nanoscale inorganic objects with biomolecules face major challenges with regard to controlling their mutual reactivity and preserving their intrinsic properties. This review describes the interactions arising between polyoxometallates or silica particles and biomolecules – including proteins, polysaccharides, lipids and nucleic acids – that depend on physicochemical conditions. It shows that chemical modification of the inorganic and/or bio-organic partner allows fine-tuning of their interface. The specific properties of these bionanocomposites are illustrated, with emphasis on their potential in biotechnology and biomedicine. This field contributes to a better understanding of the “biochemistry of solids” and offers an almost unlimited playground for the elaboration of new materials that combine molecular biodiversity with chemistry in its many facets. Understanding and controlling interfacial interactions between biological molecules – from lipids to proteins – and inorganic nano-objects, polyoxometallates and colloids allows the synthesis of bionanocomposites with applications in biotechnology and biomedicine.

Posted on 14 July 2015 | 5:52 pm

The Effects of Morphology and Linker Length on the Properties of Peptide–Lanthanide Upconversion Nanomaterials as G2 Phase Cell Cycle Inhibitors

In this work, the shape effect of our same-sized hybrid nanomaterials conjugated with two different Plk1-specific peptides had been investigated in terms of their photophysical properties, cellular uptake efficiencies, and selective inhibitory effects towards cancer and normal cells. The results clearly indicate that our spherical NaGdF4@SiO2-P1 nanoparticles achieve the best performance for in vitro imaging, G2 phase cell arrest, and, hence, cell cycle inhibition. Plk1-specific peptides are bioconjugated onto spherical and cubic NaGdF4@SiO2 nanoparticles, and the inhibitory effects of the hybrid materials towards normal cells and cancer cells are investigated.

Posted on 8 July 2015 | 10:50 am

Platinum Nanoparticles Stabilized by Glycerodendrimers: Synthesis and Application to the Hydrogenation of ?,?-Unsaturated Ketones under Mild Conditions

Air-stable platinum nanoparticles stabilized by glycerodendrimers were prepared in water and analyzed by TEM. These platinum nanoparticles showed good catalytic activity for the reduction of ?,?-unsaturated ketones to saturated ketones at room temperature in water or in water/THF (1:1) under H2 (101.3 kPa). The catalytic species was recovered and recycled several times. Pt nanoparticles are stabilized by glycerodendrimers (GD) and used (and recycled) for the reduction of ?,?-unsaturated ketones to saturated ketones at room temperature in water under H2 (101.3 kPa).

Posted on 24 June 2015 | 12:20 pm

Magnetofluorescent Nanoaggregates Incorporating Terbium(III) Complexes as Potential Bimodal Agents for Magnetic Resonance and Optical Imaging

Terbium(III) ions were coordinated to two diethylenetriaminepentaacetic acid (DTPA) amphiphilic bisamide ligands, and the complexes were assembled into micellar nanoaggregates. The magnetic and optical properties of the resulting nanoaggregates were examined in detail. Upon excitation into the ligand levels at 265 nm, the complexes show characteristic TbIII emission at 546 nm with quantum yields of up to 7.6?%. Nuclear magnetic relaxation dispersion (NMRD) measurements have shown that the transverse relaxivity r2 at 500 MHz and 310 K reaches a maximum value of 9.4 s–1?mM–1. The efficient T2 relaxivity at high magnetic field strengths is sustained by the increased rotational correlation time of the nanoaggregates and high magnetic moment of the terbium ion. Magnetofluorescent nanoaggregates incorporating amphiphilic terbium(III) complexes are created and their potential as bimodal agents for magnetic resonance and optical imaging are examined.

Posted on 23 June 2015 | 10:40 am

Uniform Poly(acrylic acid)-Functionalized Lanthanide-Doped LaVO4 Nanophosphors with High Colloidal Stability and Biocompatibility

Ln-doped (Ln = Eu or Nd) LaVO4 nanoparticles functionalized with poly(acrylic acid) (PAA) were prepared from lanthanide and vanadate precursors in the presence of PAA by a simple one-pot method that consists of a homogeneous precipitation reaction in ethylene glycol/water at a moderate temperature (120 °C). The size of the nanoparticles could be modified in the 40–70 nm range by adjusting the amount of PAA added. The effects of the Eu and Nd contents of these nanomaterials on theirs optical properties (emission intensity and lifetime) were also analyzed to find the optimum nanophosphors. Finally, the nanoparticles showed negligible cytotoxicity for Vero cells at concentrations up to 0.05 mg?mL–1 and a high colloidal stability in physiological buffer solutions; therefore, they satisfy the most important requirements for in vitro biotechnological applications. Uniform lanthanide-doped LaVO4 nanospheres functionalized with poly(acrylic acid) are synthesized with a controllable size by a one-pot procedure. As these nanoparticles present strong red (Eu) or near-infrared (Nd) luminescence, are nontoxic for cells, and show high colloidal stability in physiological buffer, they are good candidates as optical biomarkers for in vitro applications.

Posted on 22 June 2015 | 12:10 pm

Unexpected Reactivity of Red Phosphorus in Ionic Liquids

Red phosphorus is far less reactive than the white allotrope. On the other hand, it is easier to handle and not as toxic as white phosphorus. In the Lewis-acidic ionic liquid (IL) [BMIm]Cl·2AlCl3 ([BMIm] = 1-butyl-3-methylimidazolium), red phosphorus and elemental iodine form several iodides at moderate temperature. 31P liquid- and solid-state NMR spectroscopy was used to rationalize the reaction at various temperatures and ratios of the starting materials. Monitoring of the reaction revealed nanoscale red-phosphorus particles. In addition to this top-down formation, phosphorus nanoparticles were also obtained in a bottom-up synthesis by dissociation of P2I4 in the IL. Depending on the ratio of red phosphorus and iodine, as well as the reaction temperature, P2I4, PI3, or P2I5+ dominate. Red phosphorus readily reacts with iodine in a Lewis-acidic ionic liquid at moderate temperature. Besides iodides, phosphorus nanoparticles are formed. The latter are also obtained in a bottom-up process starting from P2I4. In situ liquid- and solid-state NMR spectroscopy reveals details of the reactions.

Posted on 3 June 2015 | 12:40 pm

Patent Blue Derivatized Dendronized Iron Oxide Nanoparticles for Multimodal Imaging

Dendronized nanoparticles were designed for the bimodal (optical and magnetic) detection of lymph nodes with a hand-held probe during surgery. Patent Blue VF dye and iron oxide nanoparticles with 20 nm diameter, displaying high magnetization and located at the superparamagnetic/blocked monodomain boundary, were associated through a dendritic PEGylated coating to obtain stable water suspensions. Conjugation procedures (the sulfonamide link formed between the PEGylated dendron and the dye, together with the phosphonate anchoring on the iron oxide surface) were shown to be strong enough to survive in vivo conditions when the prepared nanohybrids were tested in an inflammatory node model. Moreover, magnetization of 20 nm nanoparticles increased when dendrons were grafted onto the surface, showing that they are good candidates for magnetic particle imaging, which requires high magnetization values. Preliminary lymphatic node uptake experiments performed in an inflammatory animal model showed higher uptake of the 10 nm nanoparticles relative to that of 20 nm nanoparticles. The highest probe concentration was reached 2 d after injection. Iron oxide particles of 10 and 20 nm diameter, dendronized and derivatized with Patent Blue VF dye, survived subcutaneous injection for bimodal lymph node detection with a hand-held probe during surgery.

Posted on 2 June 2015 | 10:10 am

Long-Term Stability and Reproducibility of Magnetic Colloids are Key Issues for Steady Values of Specific Power Absorption Over Time

Virtually all clinical applications of magnetic nanoparticles (MNPs) require the formulation of biocompatible, water-based magnetic colloids. For magnetic hyperthermia, the requirements also include a high colloidal stability against precipitation and agglomeration of the constituent MNPs to maintain the heating efficiency of the ferrofluid in the long term. Agglomeration can change the heating efficiency by forming MNP clusters that modify the magnetic dipolar interactions between particles. Additionally, precipitation of the MNPs (i.e., the heating sources within the liquid) can change the measured heating rates of a colloid by altering the heat flow dynamics as the particles plunge to the precipitate. The specific power absorption (SPA) of single-domain MNPs depends critically on the average particle size and size distribution width and therefore first-rate reproducibility of different batches with respect to these parameters is also needed. We have studied the evolution of the SPA of highly reproducible and stable water-based colloids composed of polymer-coated Fe3O4 magnetic nanoparticles. By measuring the specific power absorption (SPA) values for 1 year as a function of field amplitude and frequency (H ? 24 kA/m; 260 ? f ? 830 kHz), we have demonstrated that the SPA values of these samples can be reproduced in successive synthetic batches and stable for several months due to the in situ polymer coating that provides colloidal stability and keeps dipolar interactions negligible. The poly(ethyleneimine)-coated magnetic nanoparticles (PEI-MNPs) prepared in this work by oxidative hydrolysis show good reproducibility of size and size distribution. In addition, these PEI-MNPs show only a moderate decrease in the specific power absorption when they aggregate over time. These results render these particles suitable for applications in magnetic hyperthermia.

Posted on 2 June 2015 | 10:10 am

Bio-Inspired Formation of Silica Thin Films: From Solid Substrates to Cellular Interfaces

Silica formation in biological systems (biosilicification) has been intensively studied for synthesizing inorganic materials such as silica and titania under biocompatible conditions. Inspired by biosilicification, biocompatible strategies have been developed to fabricate silica thin films on the surfaces of solid substrates such as flat wafers and micro/nanoparticles. In the search for biological applications, these strategies have been applied to cellular surfaces to coat living cells with silica or titania thin films while maintaining cell viability, and it was found that the inorganic coat is beneficial for the protection of living cells and to control cell division. This Microreview focuses on bio-inspired approaches to the formation of silica thin films on solid substrates and cellular surfaces, and includes the bio-inspired formation of other inorganic thin films that have been formed by bio-inspired silicification. The current status and future prospects of this field are also discussed. The bio-inspired formation of silica thin films on the surfaces of flat solids, microparticles, nanoparticles, and living cells is reviewed.

Posted on 19 May 2015 | 4:40 pm

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