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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:

## A Tripodal Trisilanol Ligand and Its Complexation Behavior towards CuI, CuII, and ZnII

A three-step synthetic route for a new tripodal branched trisilanol ligand PhSi(OSiPh2OH)3 (LH3) was developed. X-ray diffraction analysis revealed that the trisilanol crystallizes as a dimer with a cyclic hydrogen-bonding network. The reaction of LH3 with three equivalents of CunMesn (Mes = mesityl) led to a hexanuclear compound [L2Cu6] (1), which was characterized by single-crystal X-ray diffraction analysis as well as by solution NMR spectroscopy. The crystal structure of 1 revealed that the compound features a hexagonal planar CuI6 ring, which is the first of its kind in an oxygen environment. Deprotonation of the ligand with n-butyllithium and subsequent reaction with CuBr2 resulted in the dinuclear CuII complex [L?2Cu2][Li(THF2)]2 (2, THF = tetrahydrofuran), which contains a new siloxide ligand formed from L3– by the elimination of a SiOPh2 unit, as evidenced by X-ray diffraction analysis. To check if the “Ph2SiO” elimination is a general behavior of this trisilanol, the reaction with ZnBr2 was investigated under analogous conditions. However, this led to the isolation of [L2Zn2][Li(OEt)]2 (3) without any rearrangement of the siloxide ligand. A tripodal branched trisilanol ligand PhSi(OSiPh2OH)3 (LH3) was synthesized. Its reaction with three equivalents of CunMesn (Mes = mesityl) led to a hexanuclear compound [L2Cu6] with a planar CuI6 ring. Deprotonation of LH3 with n-butyllithium and subsequent reaction with either CuBr2 or ZnBr2 resulted in dinuclear complexes. In the case of CuBr2, the original ligand eliminates a “Ph2SiO” unit.

Posted on 12 March 2014 | 1:25 pm

## Ruthenium Halide Complexes as N-Alkylation Catalysts

A range of ruthenium-arene compounds with chloride, bromide or iodide ligands were prepared and tested as catalysts for the homogeneous redox neutral alkylation of tert-butylamine with phenethyl alcohol, and compared to the previously reported catalyst [RuCl2(p-cymene)]2, in the presence of the diphosphine 1,1?-bis(diphenylphosphino)ferrocene (dppf). The best catalytic activities were obtained with ruthenium iodide compounds. The formation of either [RuX(p-cymene)(dppf)][X] or [(RuX2(p-cymene))2(dppf)] (X = halide) under the catalytic conditions employed was investigated. Haloruthenium arene complexes have been tested as catalysts for the homogeneous redox neutral alkylation of tert-butylamine with phenethyl alcohol in the presence of 1,1?-bis(diphenylphosphino)ferrocene (dppf). Halide identity and arene substitutions influence the catalytic activity and both RuX(p-cymene)(dppf)][X] and [(RuX2(p-cymene))2(dppf)] (X = halide) appear to play a role in catalysis.

Posted on 12 March 2014 | 1:25 pm

## Masthead: Eur. J. Inorg. Chem. 8/2014

Posted on 11 March 2014 | 7:08 pm

## Bulky Titanium Amides: C–H Bond Activation under Mild Conditions

Invited for the cover of this issue is the group of Rüdiger Beckhaus at the University of Oldenburg. The cover image shows a series of titanium amide complexes synthesized in the group’s lab. These compounds undergo spontaneous C–H bond activation reactions under mild conditions. The background of the cover picture shows the Science Campus of the University. Being inspired by catalytic applications of titanium amides in organic synthesis, we are particularly interested in the relationship between structure and bonding properties...Read more about the story behind the cover in the Cover Profile and about the research itself on p. 1289 ff.

Posted on 11 March 2014 | 7:08 pm

## Spotlights on our sister journals: Eur. J. Inorg. Chem. 8/2014

Posted on 11 March 2014 | 7:08 pm

## Masthead: Eur. J. Inorg. Chem. 8/2014

Posted on 11 March 2014 | 7:08 pm

## Graphical Abstract: Eur. J. Inorg. Chem. 8/2014

Posted on 11 March 2014 | 7:08 pm

## Bulky Titanium Amides: C–H Bond Activation under Mild Conditions (Eur. J. Inorg. Chem. 8/2014)

The cover picture shows the broad chemistry of the abundant dicyclohexylamidotitanium trichloride. The remarkable crystallization properties of the light red starting material are significant for all products obtained. All variations in the coordination sphere are always accompanied by color changes. In subsequent reactions, octahedrally coordinated complexes are formed by addition of Lewis bases as well as chelating N,N?- or P,P?-ligands. An excellent proton acceptor ligand can be introduced by complexation of a sterically demanding pentafulvene. In this way, selective C–H bond activation processes are initiated, and they lead to three- or four-membered titanacycles by spontaneous b- and g-C–H elimination reactions. Details are discussed in the article by R. Beckhaus et al. on p. 1289 ff. For more on the story behind the cover research, see the Cover Profile.

Posted on 11 March 2014 | 7:08 pm

## {Cu2+–Co3+–Cu2+} and {Cu2+–Fe3+–Cu2+} Heterobimetallic Complexes and Their Catalytic Properties

We report on the heterobimetallic complexes {Cu+–Co3+–Cu+} (3), {Cu+–Fe3+–Cu+} (4), {Cu2+–Co3+–Cu2+} (5), and {Cu2+–Fe3+–Cu2+} (6) and show their catalytic applications in the oxidation of hindered phenols and the oxidative coupling of terminal alkynes. The former reaction produces C–C-coupled and dealkylated products, whereas the latter leads to the homo- and heterocoupling of terminal alkynes. The facile redox interconversion between Cu+ and Cu2+ for the secondary metal ions in these heterobimetallic complexes appears to be essential for the observed catalysis, and an important design aspect is better substrate accessibility and the use of molecular oxygen as the sole oxidant. Heterobimetallic complexes {Cu+–Co3+–Cu+} (3), {Cu+–Fe3+–Cu+} (4), {Cu2+–Co3+–Cu2+} (5), and {Cu2+–Fe3+–Cu2+} (6) have been used as catalysts for the oxidation of substituted phenols and the oxidative homo- and heterocoupling of terminal alkynes.

Posted on 11 March 2014 | 9:10 am

## Acetic Acid Mediated Synthesis of Phosphonate-Substituted Titanium Oxo Clusters

New phosphonate/acetate-substituted titanium oxo/alkoxo clusters were prepared from Ti(OiPr)4 and bis(trimethylsilyl) phosphonates in the presence of acetic acid, which served to generate water in situ through ester formation. The process led to clusters with a higher degree of condensation than in previously known phosphonate-substituted titanium oxo clusters. The clusters [Ti6O4(OiPr)10(OAc)2(O3PR)2] (OAc = acetate) were obtained for a large variety of functional and non-functional groups R under a range of reaction conditions. This cluster type, which is also retained in solution, therefore appears to be very robust. Two other clusters, [Ti5O(OiPr)11(OAc)(O3PCH2CH2CH2Br)3] and [Ti5O3(OiPr)6(OAc)4(O3P-xylyl)2], were only isolated in special cases. Several acetate/phosphonate-substituted titanium cage compounds were obtained from the reaction of titanium isopropoxide with bis(trimethylsilyl) phosphonates in the presence of acetic acid as water generator.

Posted on 11 March 2014 | 9:10 am

## Immobilization of 1,5,7-Triazabicyclo[4.4.0]dec-5-ene on Magnetic ?-Fe2O3 Nanoparticles: A Highly Recyclable and Efficient Nanocatalyst for the Synthesis of Organic Carbonates

1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic ?-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. The catalyst is quantitatively recovered by an external magnet and can be reused for six cycles with almost consistent activity. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic ?-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate.

Posted on 11 March 2014 | 9:10 am

## Binary Lithium Indides Li22–xIn8+x (x = 0.1), Li11–xIn4+x (x = 1.05), and Li10–xIn2+x (x = 1.59) with Clusters

The synthesis, structural characterization, and chemical bonding peculiarities of three new binary Li–In intermetallides are reported. The crystal structures of these compounds were determined by single-crystal X-ray diffraction analysis. The compositions obtained after structure refinements were Li22–xIn8+x (x = 0.1) [new structure type, monoclinic crystal system, Pearson symbol mS30, space group C2/m, a = 14.156(3), b = 4.729(1), c = 8.617(2) Å, ? = 105.89(1)°, R1 = 0.0279, wR2 = 0.0583 for 669 reflections], Li11–xIn4+x (x = 1.05) [new structure type, trigonal, P$\bar {3}$m1, hP15, a = 4.7480(7), c = 14.283(3) Å, R1 = 0.0323, wR2 = 0.0741 for 277 reflections], and Li10–xIn2+x (x = 1.59) [new structure type, hexagonal, P6/mmm, hP12, a = 4.6975(7), c = 11.526(2) Å, R1 = 0.0680, wR2 = 0.1358 for 127 reflections]. The Li22–xIn8+x (x = 0.1) structure is related to the structure of lithium (W-type). The structure of Li11–xIn4+x (x = 1.05) can be described as a derivative of the CdI2 type. Li10–xIn2+x (x = 1.59) can be derived from the Li2Pt structure. [In2@Li20] clusters composed of 20 lithium atoms, which surround a In–In pair, are detected in the structure of all three investigated compounds. TB-LMTO (Tight-Binding Linear Muffin-Tin Orbital) calculations indicate strong covalent In–In interactions and the presence of [In2@Li20] clusters in these new binary indides. Three new binary lithium indides were synthesized, and their crystal structures were studied by single-crystal X-ray diffraction analyses. All compounds crystallize in new structure types. The presence of [In2@Li20] clusters was detected in the structure of all three new compounds. The covalent type of the In–In bonding in the clusters was confirmed by electronic structure calculations.

Posted on 11 March 2014 | 9:10 am

## Supramolecular 3-/4-Mercaptobenzoic Acid Complexes of Palladium(II) and Platinum(II) Stabilized by Hydrogen Bonding

The reaction of cis-[Pt(PEt3)2(OTf)2] with 4-mercaptobenzoic acid (4-H2mba) in the presence of sodium methoxide yielded trans-[Pt(SC6H4COOH-4)2(PEt3)2] (1), the simple addition of 3-/4-mercaptobenzoic acid to cis-[Pt(PEt3)2(OTf)2] and cis-[M(PP)2(OTf)2] gave the self-assembled complexes cis-[Pt(?-SC6H4COOH-n)(PEt3)2]2(OTf)2 [n = 3 (2), 4 (3)] and [M(?-SC6H4COOH-n)(PP)]2(OTf)2 [M/n/PP = Pd/3/dppe (4), Pd/4/dppe (5), Pt/4/dppp (6); dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,2-bis(diphenylphosphino)propane], respectively, and the reactions of cis-[PtCl2(PR3)2] (R = Et, Ph) and [PtCl2(dppm)] with 3-/4-mercaptobenzoic acids in the presence of triethylamine yielded 1, trans-[Pt(SC6H4COOH-4)2(PPh3)2] (7) and [Pt(SC6H4COOH-n)2(dppm)] [n = 3 (8), 4 (9); dppm = bis(diphenylphosphino)methane], respectively. The complexes 1–4 and 7 form supramolecular assemblies through intermolecular hydrogen bonding in the solid state. A one-dimensional zigzag chain of carboxy dimers is formed in the structures of 1·H2O and 7, whereas methanol-interrupted large-ring formation leads to a 2D network for 1·(MeOH)2. In the cases of 3·(H2O)2 and 4·(H2O)2, water and counter-anions assisted the formation of 1D networks rather than dimers through carboxylic acid groups. 3-/4-Mercaptobenzoic acids have been employed to design Pd/Pt complexes with the general formulae trans-[Pt(SC6H4COOH-4)2(PR3)2], cis-[Pt(?-SC6H4COOH-n)(PEt3)2]2(OTf)2, [M(?-SC6H4COOH-n)(PP)2]2(OTf)2 and cis-[Pt(SC6H4COOH-n)2(dppm)]. The crystal structures and networks of these complexes have been investigated.

Posted on 10 March 2014 | 12:10 pm

## The Pentynoate Ligand as a Building Block for Multimetallic Systems

The complexes [RuRCl(CO)(BTD)(PPh3)2] (R = CH=CHtBu, CH=CHC6H4Me-4, CH=CHC5H4FeC5H5; BTD = 2,1,3-benzothiadiazole) and [Ru{C(C?CPh)=CHPh}(CO)(PPh3)2] reacted with pentynoic acid to yield the same complex, [RuCl(O2CCH2CH2C?CH)(CO)(PPh3)2], through cleavage of the vinyl ligand. In contrast, the products [RuR(O2CCH2CH2C?CH)(CO)(PPh3)2] were formed when NaO2CCH2CH2C?CH was used. An osmium example, [Os(CH=CHC6H4Me-4)(O2CCH2CH2C?CH)(CO)(PPh3)2], was also prepared from treatment of [Os(CH=CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] with NaO2CCH2CH2C?CH. Coupling of the pendant alkyne in [RuCl(O2CCH2CH2C?CH)(CO)(PPh3)2] to yield the homodimetallic complex [{RuCl(O2CCH2CH2C?C)(CO)(PPh3)2}2] was achieved by using [PdCl2(PPh3)2], CuI and NEt3. The reactivity of the alkyne unit was further exploited by the metallation of the alkyne with ClAu(PR3) (R = Ph, Cy) and Co2(CO)8 to yield the multimetallic species [Ru(CH=CHC6H4Me-4)(O2CCH2CH2C?CAuPR3)(CO)(PPh3)2] and [Ru(CH=CHC6H4Me-4)(O2CCH2CH2CC{Co2(CO)6}H)(CO)(PPh3)2]. The structures of the complexes [Ru(CH=CHC6H4Me-4)(O2CCH2CH2C?CH)(CO)(PPh3)2] and [Ru(CH=CHtBu)(O2CCH2CH2C?CH)(CO)(PPh3)2] were determined crystallographically. Organometallic ruthenium and osmium pentynoate complexes were prepared, and the pendant alkyne functionality was used to form homodimetallic and heteronuclear di- and trimetallic complexes.

Posted on 10 March 2014 | 12:10 pm

## Speciation of Technetium in Sulfuric Acid/Hydrogen Sulfide Solutions

The reaction between TcVII and H2S(g) in 12 M H2SO4 has been studied. This reaction produced a black solid and a brown supernate. The solid was analyzed by energy dispersive X-ray (EDX) and X-ray absorption fine structure (XAFS) spectroscopy and the results were consistent with the presence of Tc2S7. The speciation of technetium in the supernate was performed by UV/Visible and XAFS spectroscopy. Experiments showed that in 12 M H2SO4 an intermediate TcV sulfate complex was formed. Analysis indicated that the final complex present in solution was a polymeric species with a Tc–O–Tc core coordinated to sulfate ligands. Density Functional Theory (DFT) calculations showed that the proposed complexes were stable and that the theoretical structure was in good agreement with XAFS data. The speciation of technetium after the reaction of KTcO4 in 12 M H2SO4/H2S(g) has been studied. The mechanism of formation can be described as a transformation from the yellow species TcVIIO3(H2O)2(OH) to the green complex TcVO(HSO4)3(OH)– followed by polymerization, leading to precipitation of Tc2S7 and the presence of the polymeric species Tc–O–Tc coordinated to sulfate ligands in solution.

Posted on 7 March 2014 | 10:10 am

## Transfer Hydrogenation Catalysis by a N-Heterocyclic Carbene Iridium Complex on a Polyoxometalate Platform

A divacant Keggin polyanion has been decorated with a N-heterocyclic carbene (NHC) iridium(I) organometallic complex to provide a molecular model of an Ir-based supported catalyst. The characterization of the hybrid compound has been performed by multinuclear NMR spectroscopy, infrared spectroscopy, cyclic voltammetry, and mass spectroscopy, and the results are in agreement with a bisfunctionalization of the polyoxometalate scaffold. The resulting supported homogeneous complex has been successfully used to catalyze the transfer hydrogenation from iPrOH to benzophenone [with a turnover number (TON) of 680 and a turnover frequency (TOF) of up to 540 h–1]. A divacant Keggin polyanion has been bisfunctionalized with a N-heterocyclic carbene (NHC) iridium(I) organometallic complex, as confirmed by multinuclear NMR and mass spectroscopy. The resulting supported homogeneous complex efficiently catalyzes the transfer hydrogenation from iPrOH to benzophenone [with a turnover number (TON) of 680 and a turnover frequency (TOF) of up to 540 h–1].

Posted on 7 March 2014 | 10:10 am

## Pressure-Induced Metallic Conductivity in the Single-Component Molecular Crystal [Ni(dmit)2]

Given that a molecular system has a soft lattice, high-pressure applications are effective ways to discover new single-component molecular metals and superconductors. In this study, we measured the high-pressure electrical resistivity of a single-component molecule crystal of [Ni(dmit)2] (dmit = 1,3-dithiole-2-thione-4,5-dithiolate) up to 25.5 GPa by using a newly developed diamond anvil cell technique that generates high-quality hydrostatic pressures. We successfully observed the metallic state over a wide temperature range above 15.9 GPa. Two different band calculation methods, tight-binding calculations coupled with the interatomic repulsion model and ab initio DFT calculations, indicated that 2D and 3D Fermi surfaces appear under high pressures. Four-probe electrical resistivity measurements on the single-component molecular crystal [Ni(dmit)2] (dmit = 1,3-dithiole-2-thione-4,5-dithiolate) up to 25.5 GPa by using a diamond anvil cell (DAC) technique with high-quality hydrostatic conditions reveal a metallic state above 15.9 GPa. Ab initio DFT calculations and tight-binding band calculations indicate a 3D Fermi surface under high pressure, which explains the metallic state.

Posted on 6 March 2014 | 12:10 pm

## Synthesis, Photophysical Properties, and Self-Organization of Difurobenzosilole Derivatives

A facile synthetic route was developed to fuse furan rings to a dibenzosilole core for the construction of difurobenzosilole derivatives through an electrophilic double cyclization reaction. Only silafluorene derivatives with electron-donating groups on the periphery participated in this cyclization. Suzuki–Miyaura coupling and deiodination of the diiododifurobenzosiloles resulted in highly emissive silicon-bridged dibenzofuran compounds. These obtained compounds exhibited very high luminescent quantum yields (93 to about 99?%) and good thermal stability. Single crystals of the silicon-bridged dibenzofuran compound with a marginal phenyl group were easily grown and analyzed by single-crystal X-ray diffraction, whereas the deiodinated silicon-bridged dibenzofuran compound showed a high tendency to self-organize into 1D microfibers in various solvents such as hexane, toluene, and THF. Two difurobenzosilole derivatives are synthesized by annulation reactions. The presence of both furan and silole moieties in the ?-conjugated molecules results in extremely high fluorescence quantum yields and good thermal stability. Single crystals of one derivative are easily obtained, but the other compound shows a high tendency to self-organize into 1D microfibers in various solvents.

Posted on 6 March 2014 | 12:10 pm

## Facile Synthesis of a 20-Membered Macrocyclic Magnesium Sulfide Complex

Deprotonation of 2,3-pyrazyl-linked bis(thiophosphorano)methane {CH2(iPr2P=S)}2(C4H2N2-2,3) (2) with one equivalent of nBu2Mg in THF afforded a 20-membered macrocyclic magnesium complex [Mg{CH(iPr2P–S)}2(C4H2N2-2,3)]4 (4a). The structure of 4a has been characterized by X-ray crystallography and NMR spectroscopy. A 20-membered macrocyclic magnesium complex, [Mg{CH(iPr2P–S)}2(C4H2N2-2,3)]4, was synthesized by a one-step deprotonation of 2,3-pyrazyl-linked bis(thiophosphorano)methane {CH2(iPr2P=S)}2(C4H2N2-2,3) with one equivalent of nBu2Mg in THF.

Posted on 6 March 2014 | 12:10 pm

## Exotic 3D Hierarchical ZnO–Ag Hybrids as Recyclable Surface-Enhanced Raman Scattering Substrates for Multifold Organic Pollutant Detection

Recyclable and sensitive surface-enhanced Raman scattering (SERS) sensors for the detection of a variety of organic pollutants were fabricated from 3D hierarchical ZnO–Ag hybrids, which were synthesized by an efficient and green approach. The ZnO nanostructure could be controlled by applying a facile organic-chemical-assisted hydrothermal method. The obtained structures were then decorated with different-sized Ag nanoparticles (Ag NPs) on their side surfaces and top ends to construct 3D hierarchical ZnO–Ag nanocomposites for use as multifunctional SERS substrates. The obtained SERS sensor manifested a high sensitivity to rhodamine 6G (R6G) at a low concentration of 1?×?10–13 M and a detection limit as low as 5?×?10–9 M for the organic herbicide 4-chlorophenol (4-CP). Moreover, because of the good, stable photocatalytic properties of this exotic 3D hierarchical structure, the ZnO–Ag hybrids could self-clean under UV irradiation; this allowed repeatable SERS detection of many organic pollutants over more than three cycles with tolerable intensity attenuation. Finally, the unique repeatable detection of the organic dye R6G and the persistent organic pollutant (POP) 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrates a new route to eliminate the single-use problem of traditional SERS substrates and suggests promising applications of such materials as real-time online sensors for organic pollutant detection. Recyclable and sensitive surface-enhanced Raman scattering (SERS) sensors for the detection of organic pollutants were fabricated by an efficient and green approach from 3D hierarchical ZnO–Ag hybrids. The unique repeatable detection of rhodamine 6G (R6G) and 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrates a new route to eliminate the single-use problem of traditional SERS substrates.

Posted on 6 March 2014 | 12:10 pm

## Hierarchical N-Doped TiO2 Microspheres with Exposed (001) Facets for Enhanced Visible Light Catalysis

Hierarchical N-doped TiO2 microspheres with exposed (001) facets [N-TiO2-(001)] were synthesized through a simple, fluorine-free solvothermal reaction with subsequent thermal treatment. The results show that the hierarchical N-TiO2-(001) microspheres are made up of numerous TiO2 nanosheets, and that isopropylamine (IPAN) acts as both the nitrogen source and the capping and shape-controlling agent that generates the high-energy (001) facets. In addition, IPAN is also effective in increasing the onset temperature of the phase transformation of TiO2 from anatase to rutile. Compared with the commercially available P25 TiO2, the as-prepared TiO2 microspheres exhibit good photocatalytic activity and high stability under visible-light irradiation. The high photocatalytic performance is derived from the synergy effect of N-doping and the separation of photogenerated electrons and holes among different facets, as evidenced by surface photovoltage spectroscopy. Hierarchical N-doped TiO2 microspheres with exposed (001) facets were successfully synthesized in a fluorine-free solvothermal reaction. Isopropylamine was used as the nitrogen source and as the capping and shape-controlling agent to generate the (001) facets. The hierarchical TiO2 microspheres exhibit good photocatalytic activity and high stability under visible-light irradiation.

Posted on 6 March 2014 | 12:10 pm

## Color-Tunable Luminescence of Y4Si2N2O7:Ce3+, Tb3+, Dy3+ Phosphors Prepared by the Soft-Chemical Ammonolysis Method

Ce3+-, Tb3+-, and Dy3+-activated Y4Si2N2O7 phosphors have been prepared by the Pechini-type sol–gel method followed by ammonolysis of the precursors. The phase purity, morphology, crystallization condition, chemical composition, and thermal stability of the products have been studied carefully by X-ray diffraction (XRD), energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), fourier-transform infrared (FTIR), and thermogravimetry analysis (TGA) techniques. The photoluminescence (PL) and cathodoluminescence (CL) properties of Ce3+-, Tb3+-, and Dy3+-doped Y4Si2N2O7 phosphors were also investigated. The electronic structure of Y4Si2N2O7 has been investigated by density-functional theory methods. The calculations revealed that the nitrogen atom contributes more excited electrons than the O atom. The band gap has been calculated through the reflection spectrum of the Y4Si2N2O7 host. For Ce3+/Tb3+/Dy3+ singly doped Y4Si2N2O7 products, the phosphors give the typical emissions of the activators. The energy transfers from Ce3+ to Tb3+ and Dy3+ ions have been found and demonstrated through the PL spectra and luminescence decay times. The emission color of Y4Si2N2O7:Ce3+, Tb3+ and Y4Si2N2O7:Ce3+, Dy3+ samples can be tuned by energy transfer processes. Additionally, the temperature-dependent PL properties and the degradation property of CL under continuous electron bombardment of the as-synthesized phosphors prove that the Y4Si2N2O7 host has good stability. Therefore, the Y4Si2N2O7:Ce3+, Tb3+, Dy3+ phosphors could serve as a promising candidate for UV W-LEDs and FEDs. Preparation of Y4Si2N2O7:Ce3+, Tb3+, Dy3+ by a facile soft-chemical ammonolysis process and the electronic structure as well as the color-tunable luminescence properties of the as-prepared phosphors.

Posted on 5 March 2014 | 12:40 pm

## A Facile Strategy to Support Palladium Nanoparticles on Carbon Nanotubes, Employing Polyvinylpyrrolidone as a Surface Modifier

This paper describes the development of a facile and environmentally friendly strategy for supporting palladium nanoparticles (Pd NPs) on multiwalled carbon nanotubes (MWCNTs) with ethanol as the solvent/reducing agent, potassium tetrachloropalladate(II) (K2PdCl4) as the Pd precursor, and polyvinylpyrrolidone (PVP) as the surface modifier. More specifically, our approach was based on the nonbonding interaction between MWCNTs and PVP, which is a cheap, nontoxic, and commercial polymer. As PVP can serve not only as a surface modifier but also as a stabilizing agent for Pd NPs, the utilization of additional functionalization steps, reducing agents, and stabilizers was not required to achieve uniform Pd deposition over the MWCNTs. Our results demonstrate that Pd NPs below 5 nm in diameter can be directly supported on MWCNTs by this route. Also, sequential Pd-reduction steps can be employed to improve the coverage of Pd NPs at the MWCNT surfaces, although this can also lead to the formation of larger Pd particles or aggregates. The electrocatalytic activity for ethanol oxidation was investigated as a function of the composition and structure of the materials produced, in which MWCNTs decorated with Pd NPs of smaller sizes and lower coverages displayed the highest activities. The results described herein suggest that our approach may serve as a simple platform for the synthesis of MWCNTs decorated with metal NPs with well-defined morphologies and uniform dispersion for electrochemical and catalytic applications. The nonbonding interaction between polyvinylpyrrolidone (PVP) and multiwalled carbon nanotubes (MWCNTs) was employed to achieve deposition of palladium nanoparticles less than 5 nm in size over the surface of the MWCNTs; with ethanol as the solvent/reducing agent, potassium tetrachloropalladate(II) as the precursor, and PVP as the surface modifier.

Posted on 5 March 2014 | 12:40 pm

## Luminescent EuIII Complexes Immobilized on a Vermiculite Clay Surface

Vermiculite clays were leached with nitric acid and functionalized with (3-chloropropyl)trimethoxysilane. The resulting materials were modified with the methylimidazolium (MID) group to yield cationic surfaces. These materials were characterized by infrared spectroscopy, elemental analyses, and specific surface area. Tetrakis(?-diketonate)europate(III) complexes, [EuL4]– [L = dibenzoylmethane (DBM) and thenoyltrifluoroacetone (TTA)], were immobilized on the vermiculite surface containing the imidazolium cation to yield hybrid surfaces named Vx-MID-EuL4 (x = 0, 1, and 2), in which x represents the acid nitric concentration in mol?L–1 that is used in the leaching process. The highest luminescence intensities of the intraconfigurational-4f 5D0?7FJ transitions (for which J = 0, 1, 2, 3, and 4) arising from [EuL4]– complexes were presented by the hybrid materials containing the amount of imidazolium cation, which depend on the leaching process. The excitation and emission spectra suggested an efficient intramolecular energy-transfer process from ligand-to-Eu3+ ion in the supported materials. The photoluminescent properties of the hybrid materials were investigated based on the emission quantum efficiency (?), experimental intensity parameters ?2 and ?4, and Einstein's emission coefficient (A0J). The values of these parameters for the V2-MID-EuL4 surface are close to those assigned to the [EuL4]– isolated complexes, which indicates that hybrid vermiculite materials are promising red phosphors. Novel hybrid materials based on vermiculite and anionic lanthanide complexes electrostatically connected to 3-methyl-1-propylimidazolium have been prepared. The intramolecular ligand-to-metal energy transfers and the luminescent properties have been investigated. The values of the emission quantum efficiencies (>65?%) are the highest yet reported for lanthanide-containing clay materials.

Posted on 28 February 2014 | 5:10 pm

## Heteroleptic Group 2 Metal Precursors for Metal Oxide Thin Films

A new class of heteroleptic complexes of calcium, strontium, and barium have been synthesized using 1-{[2-(dimethylamino)ethyl](methyl)amino}-2-methylpropan-2-ol (demampH) and 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH). Complexes [{Ca(demamp)(tmhd)}2] (4), [{Sr(demamp)(tmhd)}2] (5), and [{Ba(demamp)(tmhd)}3] (6) were prepared in two-step processes. Partially substituted complexes [{Ca(demamp)(btsa)}2] (1), [{Sr(demamp)(btsa)}2] (2), and [{Ba(demamp)(btsa)}2] (3) [btsa = bis(trimethylsilyl)amide] were isolated and characterized. The molecular structures of all the compounds were studied by single-crystal X-ray crystallography. The strontium and calcium complexes have dimeric configuration with bridging of two alkoxide oxygen atoms between the metals, whereas the barium complex is a trimer. Complexes 4 and 5 show higher volatility and thermal stability with respect to the homoleptic compounds, while barium complex 6 is unstable. The TG analyses of compounds 4 and 5 display one-step curves with 9.0 and 9.6?% residue at 375 and 370 °C, respectively. A proof for the suitable selection of ligands was shown through the design of heteroleptic group 2 metal precursors. High-quality group 2 metal precursors were achieved by designing heteroleptic complexes containing suitable ligands. Even though the complexes formed as dimers, these compounds exhibit higher stability and volatility than their homoleptic monomeric forms.

Posted on 28 February 2014 | 4:10 pm

## Tuning Reductive and Oxidative Photoinduced Electron Transfer in Amide-Linked Anthraquinone–Porphyrin–Ferrocene Architectures

Porphyrin amino acids 3a–3h with meso substituents Ar of tunable electron-donating power (Ar = 4-C6H4OnBu, 4-C6H4OMe, 4-C6H4Me, Mes, C6H5, 4-C6H4F, 4-C6H4CF3, C6F5) have been linked at the N terminus to anthraquinone Q as electron acceptor through amide bonds to give Q-PAr dyads 4a–4h. These were conjugated to ferrocene Fc at the C terminus as electron donor to give the acceptor-chromophore-donor Q-PAr-Fc triads 6a–6h. To further modify the energies of the electronically excited and charge-separated states, the triads 6a–6h were metallated with zinc(II) to give the corresponding Q-(Zn)PAr-Fc triads Zn-6a–Zn-6h. The Q-PAr1 dyad (Ar1 = C6H5) was further extended with a second porphyrin PAr2 (Ar2 = 4-C6H4Me) as well as appended to a ferrocene to give the tetrad Q-PAr1-PAr2-Fc 9. Almost all the conjugates show strongly reduced fluorescence quantum yields and excited-state lifetimes, which has been interpreted as photoinduced electron transfer (PET) either from the excited porphyrin to the quinone (oxidative PET) or from the ferrocene to the excited porphyrin (reductive PET). Electrochemical data, absorption spectroscopy, steady-state emission, time-resolved fluorescence, transient absorption pump-probe spectroscopy as well as DFT calculations have been used to elaborate the preferred PET pathway (reductive vs. oxidative PET) in these architectures with systematically varied electron-donating substituents at the central chromophore. The initial photoinduced electron transfer (PET) in anthraquinone-(porphyrinAr)n-ferrocenes (n = 1, 2) is modulated by the HOMO and LUMO levels of the porphyrin chromophores by meso substituent effects. Electrochemical and spectroscopic data as well as DFT calculations were used to elaborate the preferred PET pathway in these architectures with different electron donation on the porphyrin.

Posted on 27 February 2014 | 1:10 pm

## Crystal Structure and Spectroscopic Studies of a Dimeric Europium(III) ?-Diketonate Complex Containing [3-(2-Pyridyl)-1-pyrazolyl]acetate

The homodinuclear europium(III) ?-diketonate complex [Eu2(bta)4(pypzCH2COO)2] (1) {bta = 1-benzoyl-3,3,3-trifluoroacetonate, pypzCH2COO = [3-(2-pyridyl)-1-pyrazolyl]acetate} was isolated after recrystallization of the crude product obtained from the reaction of [Eu(bta)3(H2O)2] with one equivalent of the ligand phenyl[3-(2-pyridyl)-1-pyrazolyl]acetate (pypzCH2CO2C6H5). A single-crystal X-ray diffraction study confirmed that during the recrystallization the hydrolysis of the ester group in pypzCH2CO2C6H5 took place to give pypzCH2COO–, which culminated in the crystallization of dinuclear complex 1 in which each Eu3+ ion is coordinated to two O,O?-chelated bta– groups and one N,N?-chelated pyrazolylpyridine ligand, and the two metal centers are linked by tridentate chelating–bridging (?2-?2,?1) carboxylate groups. The luminescence properties of 1 were investigated by steady-state photoluminescence (PL), PL excitation, and time-resolved PL. In the title dinuclear complex, each Eu3+ ion is coordinated to two O,O?-chelated 1-benzoyl-3,3,3-trifluoroacetonate groups and one N,N?-chelated [3-(2-pyridyl)-1-pyrazolyl]acetate ligand, and the two metal centers are linked by tridentate chelating–bridging carboxylate groups. Steady-state photoluminescence (PL), PL excitation, and time-resolved PL data are reported.

Posted on 19 February 2014 | 10:10 am

## Facile Synthesis of Multipodal MnO Nanocrystals and Their Catalytic Performance

Multipodal manganese oxide nanocrystals, synthesized through the thermal decomposition of a Mn-oleate complex, exhibited catalytic activity for the synthesis of a quinoxaline derivative from a ?-hydroxy ketone with a 1,2-diamine. The MnO nanocrystals are single crystalline and uniform multipodal, with an average estimated distance of (47?±?2) nm between the tips of two pods. Multipodal MnO nanocrystals are synthesized through thermal decomposition of a Mn-oleate complex. The MnO nanocrystals are single crystalline and uniform multipodal with an average estimated distance of (47?±?2) nm between the tips of the two pods. These nanocrystals can efficiently catalyze the synthesis of a quinoxaline derivative from an ?-hydroxy ketone with a 1,2-diamine.

Posted on 13 February 2014 | 12:10 pm

## Self-Assembly of a Mixed-Valent Co32 Ring

Solvothermal reaction of CoCl2·6H2O with H3tci [H3tci = tris(2-carboxyethyl)isocyanurate] in H2O/CH3COCH3 in the presence of triethylamine gave rise to a mixed-valent thirty-two nuclear cobalt cluster, namely, [CoII16CoIII16(?4-O)16(tci)16(H2O)12]·40H2O (1). Crystal structural analysis showed that four octanuclear [CoII4CoIII4(?4-O)4]12+ units were bridged by the carbonyl oxygen atoms of the tci3– ligands to give a Co32 ring. Magnetic studies confirmed the paramagnetic nature of this cluster, and cyclic voltammetry showed an irreversible oxidation at 1.0 V versus saturated calomel electrode. A mixed-valent 32 nuclear cyclic Co32 cluster, [CoII16CoIII16(?4-O)16(tci)16(H2O)12]·40H2O [1, H3tci = tris(2-carboxyethyl)isocyanurate], built with four octanuclear [CoII4CoIII4(?4-O)4]12+ units is synthesized and characterized. Magnetic studies confirm the paramagnetic nature, and cyclic voltammetry shows an irreversible oxidation at 1.0 V versus saturated calomel electrode.

Posted on 12 February 2014 | 12:20 pm

## Resorcinarenyl-Phosphines in Suzuki–Miyaura Cross-Coupling Reactions of Aryl Chlorides

Two phosphines built on a bowl-shaped resorcin[4]arene skeleton, namely 5-diphenylphosphanyl- and 5-diisopropylphosphanyl-4(24),6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]arene, have been synthesised and tested in the Suzuki–Miyaura cross-coupling reaction of aryl halides. Combining these ligands with [Pd(OAc)2] resulted in highly active catalysts that allowed the formation of o,o?-biphenyls starting from aryl chlorides. The remarkable activities observed possibly arise from 1) the capacity of the phosphines to operate transiently as P,O chelators, thereby increasing the electron density of the metal, and 2) the ability of the ligands to embed metal–organic units, which, when occurring, makes the ligand considerably bulkier so as to disfavour the coordination of a second phosphine. Both features are known to facilitate the oxidative addition step. Palladium complexes containing cavitand-phosphines based on a resorcinarene skeleton display high reactivity in Suzuki–Miyaura cross-coupling reactions. The unusual performance of these ligands essentially relies on their bulkiness and ability to bind the metal centre in a hemilabile fashion.

Posted on 6 February 2014 | 4:13 pm

## Homoleptic Copper(I), Silver(I), and Gold(I) Bisphosphine Complexes

A series of homoleptic copper(I), silver(I), and gold(I) complexes of two bisphosphine ligands {1,2-bis(diphenylphosphino)benzene, dppb; bis[2-(diphenylphosphino)phenyl]ether, POP} have been prepared. Whilst all three [M(dppb)2]BF4 complexes are tetracoordinate, this geometry is found only for the silver(I) complex with POP. Instead, [Cu(POP)2]+ and [Au(POP)2]+ adopt a trigonal coordination geometry with an uncoordinated phosphorus atom. A close inspection of the P–M bond lengths reveals an interesting trend. From the copper to silver and gold complexes, a substantial elongation is found. On the other hand, from the silver to gold compounds, a decrease in the M–P bond length is found. Indeed, gold(I) has a smaller van der Waals radius than silver(I) as a result of its peculiar relativistic effects. Electrochemical investigations revealed two oxidation processes for all of the [M(dppb)2]BF4 and [M(POP)2]BF4 complexes. The first oxidation is likely metal-centered, whereas the second one corresponds to ligand-centered processes in all cases. The emission properties of these compounds in solution, in frozen rigid matrices at 77 K, and in the solid state at room temperature have been systematically investigated. Although all of them are weak emitters in solution, remarkably high emission quantum yields were found in the solid state, in particular for [Cu(dppb)2]BF4 and [Ag(dppb)2]BF4. Finally, these two compounds were used for the fabrication of light-emitting devices. Interestingly, both the copper(I) and the silver(I) complex afford quite broad electroluminescence spectra with white light emission. Copper(I), silver(I), and gold(I) [M(PP)2]BF4 complexes have been prepared from two bisphosphine ligands, namely, 1,2-bis(diphenylphosphino)benzene (dppb) and bis[2-(diphenylphosphino)phenyl]ether (POP). Their electronic properties have been systematically investigated and rationalized as a combination of steric and electronic effects as well as by differences in their coordination geometries.

Posted on 6 February 2014 | 4:13 pm

## Crystal Chemistry of Uranyl Carboxylate Coordination Networks Obtained in the Presence of Organic Amine Molecules

Three uranyl isophthalates (1,3-bdc) and two uranyl pyromellitates (btec) of coordination-polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine-based molecules [1,3-diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N-dimethylformamide]. (UO2)2(OH)2(H2O)(1,3-bdc)·H2O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H2O molecules. The compounds (UO2)1.5(H2O)(1,3-bdc)2·0.5H2dap·1.5H2O (2) and UO2(1,3-bdc)1.5·0.5H2dap·2H2O (3) consist of discrete uranyl-centered hexagonal bipyramids connected to each other by a ditopic linker to form a single-layer network for 2 or a double-layer network for 3. The protonated diamine molecules are located between the uranyl–organic sheets and balance the negative charge of the layered sub-networks. The phase (UO2)2O(btec)·2Hdma·H2O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO2(btec)·2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non-bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen-bond network. The different illustrations show the structural diversity of uranyl–organic coordination polymers with organic amine molecules as countercations. A new series of uranyl–organic carboxylates has been hydrothermally synthesized by using isophthalic or pyromelitic acid in the presence of 1,3-diaminopropane or a DMF/water solvent mixture. Their crystal structures revealed 1D and 2D coordination networks, which may intercalate protonated propanediammonium or dimethylammonium (from in situ thermal decomposition of DMF) species.

Posted on 6 February 2014 | 4:13 pm

## Iodo(trisyl)sulfane: Reactivity of a Stable Alkanesulfenyl Iodide towards Antithyroid Drugs

Iodination of tris(trimethylsilyl)methanethiol (trisylthiol, TsiSH) in tetrahydrofuran provides the new thermally stable alkanesulfenyl iodide [iodo(trisyl)sulfane, TsiSI] as a violet solid. Iodo(trisyl)sulfane exhibits iodine–iodine contacts between pairs of TsiSI molecules in the solid state. Properties of TsiSI were studied by vibrational spectroscopy and with the help of density functional calculations. TsiSI reacts in the presence of triethylamine with the antithyroid drugs 6-n-propyl- and 6-methylthiouracil (PTU, MTU) and with N-methylmethimazole (MMI) to form unsymmetric disulfides that were investigated by means of X-ray crystallography. In the solid state, the PTU and MTU derivatives exist as hydrogen-bonded centrosymmetric dimers, whereas the MMI-derived disulfide is an unsymmetric monomer. Iodination of tris(trimethylsilyl)methanethiol (TsiSH) in tetrahydrofuran provides stable violet iodo(trisyl)sulfane (TsiSI) 3, which exhibits iodine–iodine contacts between pairs of TsiSI molecules in the solid state. TsiSI reacts with the antithyroid drugs 6-n-propyl- and 6-methylthiouracil (PTU, MTU) and with methylmethimazole (MMI) to deliver unsymmetric disulfides like Tsi-S-S-PTU.

Posted on 6 February 2014 | 4:13 pm

## Speciation Behavior of Copper(II) Acetate in Simple Organic Solvents – Revealing the Effect of Trace Water

Copper(II) acetate is frequently used as a catalyst for bond-forming reactions in organic synthesis. Unlike aqueous solutions, in which complete heterolysis to CuOAc+(aq) and AcO–(aq) prevails at low concentrations, it is clear that copper(II) acetate shows a large degree of aggregation in typical organic solvents. Here, the speciation behavior of Cu(OAc)2 in organic solvents is probed by electrospray ionization mass spectrometry (ESI-MS), which reveals an extensive clustering of copper acetate species to form ions of the general composition [Cun(X)2n–1]+ and [Cun(X)2n+1]– (X = OAc and OCH3), along with (solvated) monomeric species such as [Cu(OAc)(CH3OH)n]+. The ESI-MS measurements are complemented by solution-phase studies of Cu(OAc)2 by electron paramagnetic resonance spectroscopy, which support an extensive aggregation of Cu(OAc)2 in organic solvents. Collisional experiments reveal that either simple degradation or redox processes can be observed, depending on the coordinative saturation of the copper clusters. The formation of the copper clusters can be efficiently suppressed by contamination of the organic solvents by a small amount of water. Understanding catalyst behavior: Copper(II) acetate tents to aggregate extensively in organic solvents. However, even trace amounts of water can efficiently suppress the aggregation. This finding is supported by ESI-MS and electron paramagnetic resonance (EPR) measurements.

Posted on 6 February 2014 | 4:13 pm

## Syntheses and Structures of Potassium Complexes Containing Bis(diphenylphosphanyl)methanide Anions

The reaction of [K{(Ph2P)2CH}(Et2O)0.5]n with an excess of tetrahydropyran yields polymeric [K{(Ph2P)2CH}(thp)]? (1). Application of neutral bidentate ligands such as dimethoxyethane or N,N,N?N?-tetramethylethylenediamine leads to a splitting of the polymeric starting material into discrete dinuclear entities and the complexes [K{(Ph2P)2CH}(dme)]2 (3) and [K{(Ph2P)2CH}(tmeda)]2 (4) were isolated. In compounds 1, 3 and 4, the phosphorus atoms as well as the methanide carbon atom and two of the four phenyl groups of the anionic ligand participate in metal binding. Oligodentate ligands such as diglyme and 18-crown-6 enforce a reduction of the interaction between potassium and the diphosphanylmethanide anion and lead to the mononuclear complexes [K{(Ph2P)2CH}(diglyme)2] (5) and [{K{(Ph2P)2CH}(18C6)}{K{(Ph2P)2CH}(18C6)(thf)}] (6), respectively. In these compounds, only the phosphorus atoms of the diphosphanylmethanide ligands coordinate to the central potassium cation. The related lithium derivative [Li{(Ph2P)2CH}(thp)3] (2) was prepared for comparison. All complexes were characterized by NMR methods and X-ray diffraction measurements. The disaggregation of polymeric potassium bis(diphenylphosphanyl)methanide into discrete mono- or dinuclear entities as well as the resulting changes in coordination mode of the anionic ligand were studied. The process depends on the nature of the mono-, bi- and oligodentate neutral oxygen or nitrogen donor ligand added.

Posted on 4 February 2014 | 2:10 pm

## Experimental and Theoretical Investigations of the Ternary Boride NbRuB with a Layerlike Structure Type

Powder samples and single crystals of the new ternary compound NbRuB were synthesized by arc-melting of the elements in a water-cooled crucible under an argon atmosphere. The samples have been characterized by X-ray diffraction and energy-dispersive X-ray spectroscopy (EDX) measurements. Furthermore, the crystallographic, electronic, and bonding characteristics have been studied by density functional theory. The title compound crystallizes with a new orthorhombic structure type in the space group Pmma (no. 51) with the lattice parameters a = 10.870(2) Å, b = 3.173(1) Å, and c = 6.350(2) Å. The structure consists of two kinds of atomic layers: the first layer (at y = 0) contains niobium atoms and isolated boron atoms, and the second (at y = 0.5) contains ruthenium atoms and boron dumbbells. Electronic structure relaxation has confirmed the crystallographic parameters, and crystal orbital Hamilton population (COHP) bonding analysis indicates that the B–B bond is the strongest bond, but the numerous and relatively strong metal–boron and Nb–Ru bonds are responsible for the overall stability and indicate a three-dimensional bonding character in the new compound. NbRuB has a new intergrowth crystal structure, which contains Re3B- and AlB2-type structures. DFT calculations indicate a deep pseudogap in its density of states (DOS) curve and predict isoelectronic and electron-poorer phases. Bonding analysis indicates that the B2 dumbbell is the strongest bond, but the interlayer Nb–B, Ru–B, and Ru–Nb bonds are responsible for the structural stability.

Posted on 4 February 2014 | 2:10 pm

## Broadly Tunable Emission from CaMoO4:Bi Phosphor Based on Locally Modifying the Microenvironment Around Bi3+ Ions

The trivalent green element of bismuth, when doped into different compounds, can produce multiple emissions in ultraviolet, blue, green or even yellow spectral regimes. The emission adjustability comes from the susceptibility of bismuth naked 6s electrons to the crystal field particularly surrounding Bi3+. However, this has never been observed in a single compound. In this work, we report that broadly tunable bismuth emission indeed occurs even within the same host (CaMoO4) when the local microenvironment around Bi3+ is modified by intentional introduction of alkali ions. As the radius of the selected alkali ion decreases, the emission regularly blue-shifts from 586 to 554 nm, and its intensity is enhanced greatly. For instance, the integrated intensity for the Li+ and Bi3+ codoped sample is 4.46 times stronger than the Bi3+ single-doped sample upon excitation at 300 nm. Low-temperature photoluminescence spectra surprisingly reveal that energy transfer can partially take place from the MoO42– group to Bi3+ at lower temperature when excited into the charge transfer state of the MoO42– group, however, this does not occur at higher temperature. The mechanism needs further study. Dynamic luminescence analysis between 10 and 300 K implies a population dependence of the excited states 3P0 and 3P1 on temperature that is responsible for the evolution of the Bi3+ emission lifetime with temperature. Broadly tunable bismuth emission is observed in the host CaMoO4 when the local microenvironment around Bi3+ is modified by alkali ions. Energy transfer can take place from the MoO42– group to Bi3+ at lower temperature but not at higher temperature. The dependence of the excited states 3P0 and 3P1 on temperature is responsible for the evolution of the Bi3+ emission lifetime with temperature.

Posted on 4 February 2014 | 2:10 pm

## Bulky Titanium Amides: C–H Bond Activation under Mild Conditions

The bulky titanium monoamido complex Cl3TiNCy2 (1) was synthesized from TiCl4 and dicyclohexylamine (Cy2NH). The solid-state structure of 1 demonstrates a close intramolecular contact between the metal centre and one ipso carbon atom of the amido ligand. This contact may indicate an agostic interaction analogous to those of transition metal alkyl compounds. The alteration of the coordination sphere of 1 with neutral ligands [pyridine (2), 2,2?-bipyridyl (3), N,N,N?,N?-tetramethylethane-1,2-diamine (tmeda, 4), and 1,2-bis(dimethylphosphanyl)ethane (dmpe, 5)] results in octahedral compounds with a meridional arrangement of the ligands. The solid-state structure of 5 reveals a significantly closer contact between the titanium atom and one ipso carbon atom of the ligand. The magnesium reduction of 1 in the presence of adamantylidenepentafulvene yields the dark green complex (?5,?1-adamantylidenepentafulvene)Ti(NCy2)Cl (8). The exchange of the last chlorine atom with other bulky amido ligands [NCy2, N(SiMe3)2] by salt metathesis reactions initiates a spontaneous C–H activation at room temperature. The titanaaziridine (?5-CpAd)(?2-NCy2)TiNCy2 (9) formed after a ?-C–H activation with LiNCy2. The use of NaN(SiMe3)2 results in a ?-C–H activation and the formation of the azatitanacyclobutane (10). The alkylation of ClTi(NCy2)3 (7) with methyllithium produces the reactive complex MeTi(NCy2)3 (11). The spontaneous reaction of 11 at room temperature by ?-C–H activation to release methane and cyclohexene yields the dinuclear imido-bridged complex [(Cy2N)2Ti(NCy)]2 (12). The formation of 12 can also be observed by 1H NMR spectroscopic measurements. The solid-state structures of tetrahedral and octahedral titanium amide complexes with bulky dicyclohexylamido ligands reveal a characteristic close contact between the titanium atom and a carbon atom in the ?-position. The exchange of a chlorine atom by a bulky pentafulvene ligand increases this effect. The introduction of other sterically demanding amines to complexes initiates a spontaneous C–H activation.

Posted on 3 February 2014 | 4:30 pm

## Quasi-Planar Organic Synthon and S···X (X = S or H–C) Contacts in Flat Copper Coordination Chains: Syntheses, Structures and Conductive Behaviour

A new organic building block, TEPB, has been synthesized that comprises three 2-ethylthio-substituted pyrimidine groups coupled to one central phenyl ring at the 1-, 3- and 5-positions. TEPB exhibits a quasi-planar conformation due to its intramolecular C–H···N hydrogen bonds. The assembly of TEPB with CuI and CuCl2 produced two flat coordination chains 1 and 2, both exhibiting similar assembly hierarchies from chain through 2D layer to 3D architecture. It was found that extensive S···S and C–H···S contacts exist in the 2D layers of 1 and 2, respectively. Between the 2D layers of 2, there are O–H···Cl hydrogen-bonding interactions between water molecules and coordinated Cl atoms that provide a proton-transfer network. Complex 2 exhibits a smaller optical band gap (1.11 eV) than 1 (1.93 eV), which has been attributed to d-electron transition in the copper(II) ion. The d.c. conductivities of 1 and 2 at room temperature were measured to be 2.84?×?10–12 and 2.42?×?10–10?S?cm–1, respectively. The a.c. conductivity of 2 obtained at room temperature by the complex impedance technique is about 5.90?×?10–9?S?cm–1, which can be attributed largely to proton conduction. Moreover, the a.c. conductivity of 2 decreases almost linearly with increasing temperature, presumably as a result of its temperature-sensitive O–H···Cl hydrogen-bonding network that allows for proton conduction. The assembly of quasi-planar organic synthon TEPB with CuI and CuCl2 produced two flat coordination chain structures (1 and 2) that incorporate S···S and C–H···S contacts in their packing structures. Complex 1 is an insulator, whereas 2 shows conductive properties with an a.c. conductivity of 5.90?×?10–9?S?cm–1 at room temperature.

Posted on 3 February 2014 | 3:40 pm

## Base-Catalyzed Hydrolysis of a RuII–Chloro–dmso Complex and Its Reactivity towards L-Methionine

The ruthenium(II) complex cis-[RuCl2(dmso)4] is known for its antiproliferative properties. This has stimulated the discovery of a wide group of new ruthenium complexes considered as potential anticancer drugs. The stability of these ruthenium complexes under physiological conditions and their interaction with protein amino acid residues are particularly important because of their intravenous administration. The studies presented here are devoted to the stability of cis-[RuCl2(dmso)4] under physiological pH conditions and its reactivity towards L-methionine. Immediate dissociation of one dmso ligand from the parent complex after dilution in water leads to the formation of fac-[RuCl2(H2O)(dmso)3], which under basic conditions undergoes stepwise dissociation of chloride ions without further dmso release. The hydrolysis of fac-[RuCl2(H2O)(dmso)3] at pH 7.4 and also base-catalyzed hydrolysis were investigated in detail by application of kinetic and spectroscopic (UV/Vis, NMR) measurements. The combined experimental and theoretical study revealed that L-methionine coordinates to fac-[RuCl(OH)(H2O)(dmso)3] by substituting a water ligand with simultaneous dmso release. Detailed NMR characterization of the product indicated that methionine coordinates through the NH2 group rather than the thioether moiety. This conclusion was further supported by theoretical calculations with the application of ETS–NOCV analysis. Detailed NMR characterization of the reaction product with L-methionine, supported by theoretical calculations, indicated that the NH2 group is the primary target for coordination to the metal center and not the thioether moiety.

Posted on 3 February 2014 | 3:30 pm

## N,N?-Bis(2,6-diisopropylphenyl)benzamidinates and -pivalamidinates of the s-Block Metals Lithium, Potassium, and Calcium

Metalation of N,N?-bis(2,6-diisopropylphenyl)benzamidine (1a) and -pivalamidine (1b) in tetrahydrofuran (THF) with n-butyllithium and potassium bis(trimethylsilyl)amide gives the corresponding N,N?-bis(2,6-diisopropylphenyl)benzamidinates and -pivalamidinates of lithium, [(thf)2Li{(Dipp-N)2C-Ph}] (2a) and [(thf)Li{(Dipp-N)2C-tBu}] (2b), as well as of potassium, [(thf)3K{(Dipp-N)2C-Ph}] (3a) and [(thf)3K{(Dipp-N)2C-tBu}] (3b) (Dipp = 2,6-diisopropylphenyl). Because metalation of these amidines is not possible with [(thf)2Ca{N(SiMe3)2}2], a metathetical approach has been chosen. Hence, the reaction of 3a with calcium iodide in THF yields (tetrahydrofuran)calcium bis[N,N?-bis(2,6-diisopropylphenyl)benzamidinate] (4a). For the bulkier N,N?-bis(2,6-diisopropylphenyl)pivalamidinate, heteroleptic [(thf)Ca{(Dipp-N)2C-tBu}{N(SiMe3)2}] (4b) forms. Depending on the softness and charge-to-radius ratio, syn configuration of the amidinate ligands is observed for 2a, 4a, and 4b, whereas the anti configuration is realized in complexes 2b, 3a, and 3b, the latter being stabilized by intramolecular metal–? interactions. Depending on the hardness of the s-block metals, the coordination behavior of substituted N,N?-bis(diisopropylphenyl)amidinates vary. Hard cations favor the nitrogen bases whereas soft cations bind to the ?-systems of the aryl groups (C gray, Li green, N blue, O red).

Posted on 31 January 2014 | 11:30 am

## Near-IR Sensitization of Dye-Sensitized Solar Cells Using Thiocyanate-Free Cyclometalated Ruthenium(II) Complexes Having a Pyridylquinoline Ligand

Three thiocyanate-free cyclometalated ruthenium(II) complexes, [Ru(dcpq)2(CN)]Cl [where dcpq is 2-(4?-carboxypyridin-2?-yl)quinoline-4-carboxylic acid and C?N is a bidentate cyclometalating ligand] (compounds FT22, FT23, and FT61), were designed and synthesized as near-IR (NIR) sensitizers for dye-sensitized solar cells (DSSCs) to investigate the effect of the ligand structure on the photovoltaic performance. Density functional theory calculations of these complexes show that the highest occupied molecular orbital is mainly localized on the metal center with the C?N ligand, and the lowest unoccupied molecular orbital is mainly localized on the anchoring dcpq ligand. These complexes exhibit a broad absorption band and superior light-harvesting properties in the NIR region. FT22-, FT23-, and FT61-based DSSCs exhibit efficiencies of 3.81, 3.43, and 5.53?%, respectively. The modification of the C?N ligand improves the photovoltaic performance of this class of cyclometalated ruthenium(II) complexes. The DSSC sensitized with FT61 exhibited a 25?% incident photon-to-current conversion efficiency at 900 nm. Three thiocyanate-free cyclometalated ruthenium(II) complexes were designed and synthesized as near-IR sensitizers for dye-sensitized solar cells. The modification of the ligand structure can improve the photovoltaic performance of this class of cyclometalated ruthenium(II) complexes.

Posted on 31 January 2014 | 11:23 am

## A Phosphino Calix[4]arene Bis-Frustrated Lewis Pair

A bis-frustrated Lewis pair based on a calix[4]arene skeleton is reported for the first time. Importantly, this system has been shown to activate two molecules of hydrogen, thereby establishing a proof of concept for multisite frustrated Lewis pair (FLP) design and synthesis. The complex [calixarene-(Mes2PH+)2][BH(C6F5)3–]2 (6) has been characterised by X-ray crystal structure analysis. The synthesis and X-ray structure of a calix[4]arene bis-frustrated Lewis pair is described for the first time. This compound is the first example of a frustrated Lewis pair system capable of doubly activating H2 as well as the first use of a calixarene in frustrated Lewis pair chemistry.

Posted on 31 January 2014 | 11:23 am

## Copper(I) Complexes of Phenanthro-Annulated N-Heterocyclic Carbenes: Synthesis and Transmetalation Reactions

Copper(I) complexes with phenanthro-annulated N-heterocyclic carbene ligands were prepared by reaction of imidazolium salts with copper(I) oxide. Transmetalation of the copper complexes with [RhCl(cod)]2 in usual solvents like CH2Cl2 led to an equilibrium between the reactants and the products. For rhodium complexes 4 and 5 this equilibrium could be shifted to the product side by carrying out the reaction in acetonitrile. The ester functionalized rhodium complex 6 was prepared in a two phase mixture of chloroform and aqueous CaCl2 starting from copper complex 3c. The rhodium complexes were characterized by NMR and X-ray measurements. Copper complexes with phenanthro-annulated N-heterocyclic carbene ligands were prepared from imidazolium salts and Cu2O. Initial transmetalation experiments with [RhCl(cod)] showed an equilibrium in most solvents. Two rhodium complexes could be prepared using acetonitrile as the solvent. One was prepared in a two phase mixture of chloroform and aqueous CaCl2.

Posted on 30 January 2014 | 10:20 am

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