Synthesis and properties of charge-transfer complexes based on quaternary salts of amines and tetracyanoquinodimethane

The electrical and optical properties of four charge-transfer complexes based on a molecule of tetracyanoquinodimethane (an acceptor) and donor molecules of quaternary salts of amines have been studied. It has been shown that the conductivity of the complexes has a semiconductor character and is determined by conduction along stacks of tetracyanoquinodimethane molecules.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 1, pp. 102–105, January–February, 1986.     

Synthesis and characterization of noble-metal-substituted Dawson-type polyoxometalates

Polyoxometalates substituted by noble metal cations (PdII, RuIII, IrIV) of general formula (Bu4N)n[P2W17M(OH2)O61] are prepared by refilling the vacant site of the lacunary precursor 2-K10P2W17O61. Both 31P- and 183W-n.m.r. studies provide convincing evidence for the above structural assignment. The u.v.-vis and i.r. spectra are consistent with the first row transition metal substituted homologues. Electrochemical investigations by cyclic voltammetry in MeCN revealed four reversible one-electron redox couples, which are ascribed to the tungsten(VIV) process of the tungsten-oxo framework.     

Synthesis, characterization, and crystal structures of two novel high-nuclear nickel-substituted dimeric polyoxometalates

Two novel high-nuclear Ni-substituted polyoxometalates Na9K[Ni7(OH)4(H2O)(CO3)2(HCO3)(A-alpha-SiW9O34)(beta-SiW10O37)].5H3O.18H2O (1) and K6Na4[{Ni6(H2O)4(mu2-H2O)4(mu3-OH)2}(x-SiW9O34)2].17.5H2O (2) have been obtained by reaction of K(8)[gamma-SiW10O36] with NiCl2.2H2O in basic conditions. Compounds 1 and 2 all represent the first polyoxometalates substituted by seven and six Ni centers, respectively. Also, compound 1 exhibits a novel asymmetric dimeric structure, composed of [A-alpha-SiW9O34]10- and [beta-SiW10O37]10- units linked by a Ni7 cluster and three carbonates, which exhibit tri- and bidentate coordination modes in 1.     

Preparation parameter development for layer-by-layer assembly of Keggin-type polyoxometalates

Polyoxometalates possess many useful properties for electrochemical catalysis. These molecule-size clusters can be assembled into thin films through the layer-by-layer method. In this study, we determined a cluster concentration range within which layer-by-layer (LbL) films have been successfully fabricated. We also find the influence of salt added to the deposition solutions. In an attempt to understand the self-assembly process at the molecular level, thermodynamic arguments, derived from complexation between nanoscale particles and oppositely charged polyelectrolyte chains, have been employed to interpret the adsorption of polyoxometalate clusters onto a cationic polymer layer. The scaling results describe the contact mode between a polymer chain and a cluster. The assembly can be visualized with assistance by understanding the contact between the polymer chain and the cluster.     

Catalytic effects of some Keggin-type heteropoly acids and polyoxometalates on selective nitration of phenols

Catalytic amounts of heteropoly acids and polyoxometalates promoted mononitration of phenolic compounds using iron(III) nitrate nonahydrate and bismuth(III) nitrate pentahydrate in dichloromethane at room temperature. Tungstophosphoric acid cesium salt, Cs_2.5H_0.5PW₁₂O₄₀, in a heterogeneous phase, exhibited significant rate enhancement of reactions as well as ortho selectivity without over-nitration and oxidation byproducts.     

Synthesis and properties of catechol-fused tetrathiafulvalene derivatives and their hydrogen-bonded conductive charge-transfer salts

Catechol-fused tetrathiafulvalene (TTF) derivatives have been designed and synthesized as a new type of π-electron donor molecules having two phenolic hydroxyl groups. Cyclic voltammetry measurements and quantum chemical calculations demonstrated the electronic effect of the direct fusion of the catechol unit to the TTF π-skeleton. In the charge-transfer (CT) salts with bromide or chloride anions, a one-dimensional hydrogen-bonded chain was formed by the intermolecular OH?X network between the catechol moieties and the halide anions. The slight dissimilarity of the hydrogen-bond distances for the two CT salts gave rise to the significant differences in their overall molecular arrangements and intermolecular interactions as well as the electrical resistivities.     

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes

Two new hybrid compounds based on Keggin-type polyoxometalates: {[PMo₁₂O₄₀][Ni(Phen)₂(H₂O)]₂}·K·2OH⁻ (1) and [Cd₂(Phen)₄Cl₂][HPW₁₂O₄₀]·H₂O (2) (Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K⁺ ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW₁₂O₄₀]²⁻ and novel metal-chloride-ligand coordination complexes [Cd₂(Phen)₄Cl₂]²⁺.     

Yttrium polyoxometalates. Synthesis and characterization of a carbonate-encapsulated sandwich-type complex

Reaction of A-alpha-PW(9)O(34)(9)(-) with YCl(3) in an aqueous Na(2)CO(3) solution produces a dianion-encapsulated A-type sandwich polyoxometalate, (YOH(2))(3)(CO(3))(A-alpha-PW(9)O(34))(2)(11)(-). The X-ray structure of this complex reveals that three Y(III) ions are sandwiched between two A-alpha-PW(9)O(34)(9)(-) moieties and that a carbonate dianion is encapsulated in the same plane as the three Y(III) atoms. The oxygen atoms of the CO(3)(2)(-) are sitting at the midpoints of the sides of the triangle formed by the three Y(III) ions. (31)P and (13)C NMR studies confirm that this complex is significantly more stable than the analogous A-type sandwich polyoxometalates containing divalent metals.     

Synthesis and characterization of new triazenide salts

Stable triethylammonium triazenide salts were obtained on treatment of the appropriate triazenes with triethylamine. Those salts are described and fully characterized for the first time and are used for the preparation of alkoxycarbonylvinyltriethylammonium triazenides, which are prone to transesterification.     

Synthesis and conductivity of hybrid materials based on germanium-containing polyoxometalates and ionic liquids

Three new compounds, [MIMPS]₅GeW₁₁VO₄₀, [MIMPS]₅GeW₁₀MoVO₄₀, and [MIMPS]₅GeMo₁₁VO₄₀, have been synthesized from 1-(3-sulfonic group) propyl-3-methyl imidazolium (MIMPS, C₇H₁₃N₂O₃) and germanium-containing heteropoly acids H₅GeW₁₁VO₄₀, H₅GeW₁₀MoVO₄₀, and H₅GeMo₁₁VO₄₀. IR spectra indicate the formation of the hybrid molecular compounds showing fingerprint vibrational bands of both heteropolyanions and MIMPS cations. The products exhibit high conductivity and small conductive activation energies; conductivities increase with higher temperature. Their conductivities are as follows: [MIMPS]₅GeW₁₁VO₄₀?>?[MIMPS]₅GeW₁₀MoVO₄₀?>?[MIMPS]₅GeMo₁₁VO₄₀. The sequence is opposite for their conductive activation energies. The results show that the conductivity and conductive activation energies are closely related to their component elements. The W-containing material exhibits higher conductivity and smaller conductive activation energy than Mo-containing material.     

Synthesis of Keggin-type polyoxometalate crystals

Vanadium-containing polyoxometalates (POM) were synthesized under acidic conditions and characterized by XRD, FT-IR, ⁵¹V MAS-NMR, EXAFS-XANES and SEM.POM crystals were successfully grown under acidic atmosphere, thus forming a self-assembled structure. This self-organized structure was constituted by cubic crystals having between 20 and 80 μm in size.Both ⁵¹V MAS-NMR, EXAFS-XANES and PM6 calculations suggest that non-covalent interactions, such as hydrogen bonding, or shared vanadium atoms of non-complete coordination are the driving force of the self-assembly process.     

Synthesis,spectroscopic characterization and redox properties of titanium and vanadium substituted Keggin-type heteropolyanions

The Ti-substituted heteropolytungstates K7[TiIVW11–BO40] and K6[VVTiIVW10PO40] have been synthesized and characterized by elemental analyses and spectroscopic techniques. Their redox properties have been studied by cyclic voltammetry, and the compounds were found to be more difficult to reduce than the unsubstituted heteropolyanion. The one- and two-electron reduced heteropoly blues of [VVTiIVW10PO40]6–, namely [VIVTiIVW10PO40]7– and [VIVTiIIIW10PO40]8–, have also been prepared by chemical methods. Their optical spectra show low-energy intervalence charge-transfer bands as well as the expected d–d transitions. The optical and e.s.r. investigations indicate that VIV and TiIII are not vicinal in [VIVTiIIIW10PO40]8–.     

Synthesis and characterization of triphenylmethylphosphonium transition metal salts

Triphenylmethylphosphonium salts, [PPh3Me]aMXn (M=Cu2+, Co2+, Mn2+, Ni2+ Fe3+ Pb2+ and Hg2+; X=Cl or I; a=1 or 2 and n=3 or 4) prepared by reacting PPh3MeX with the metal dihalide in EtOH sol-utions, have been characterized by electronic, Raman, far i.r. and Mo¨ssbaur spectra and by their magnetic properties as well as by elemental analyses. The copper complexes [PPh3Me]2CuCl4 and [PPh3Me]2Cu3Cl8 were characterized by X-ray crystallography and the structures are described. Powder diffraction patterns have shown that the cobalt and manganese tetrachloride complexes are isomorphous. Investigation by d.s.c. measurements showed that the complexes exhibit structural phase transitions.     

Synthesis and characterization of polymer networks based on two kinds of macromonomer

pH-sensitive networks were obtained by radical copolymerization of telechelic poly(1,3-dioxolane) (PDXL) with acrylic acid (AA). The PDXL bismacromonomer was synthesized by two methods: one (PDXLDA) by acrylation of the corresponding dihydroxylated PDXL with AA in pyridine; the other (PDXLHM) by adding 2-hydroxyethylmethacrylate as a transfer agent during the cationic polymerization of 1,3-dioxolane (DXL). The copolymer networks of poly(AA-b1-DXL) and poly(AA-b2-DXL) prepared by PDXLDA and PDXLHM macromonomers with AA, respectively, have very different physical properties. Poly(AA-b1-DXL) networks are pH-sensitive, while poly(AA-b2-DXL) ones are not. The poly(AA-b1-DXL) networks degrade easily under acidic condition, while poly(AA-b2-DXL) ones do not. The great differences between the properties of the networks depend on the network structure, which is directly related to the corresponding bismacromonomer structure. Microphase separation in all the networks can be observed by scanning electron microscopy. The network structure, swelling behavior and degradation were characterized by Fourier transform IR spectroscopy, differential scanning calorimetry, scanning electron microscopy and swelling data.     

Effects of Cs-substitution and partial reduction on catalytic performance of Keggin-type phosphomolybdic polyoxometalates for selective oxidation of isobutane

The catalytic performance of Cs-substituted phosphomolybdic salts was studied for selective oxidation of isobutane. The results of activity tests revealed that 360 °C was the optimal reaction temperature. It was demonstrated that oxidizing sites not only took dominating part in the activation of isobutane, but also influenced the product distribution. Besides, appropriate Cs addition led to moderate acidity of catalysts, favoring the selectivity to desired products. Furthermore, to obtain partially reduced catalysts, different calcination atmospheres were investigated and certain proportion of Mo~(5+) produced during calcination was crucial for the redox reaction. The catalyst calcined in N_2 showed the highest yield of MAA(7.0%). Fe-substitution enhanced the activity of catalysts by rapid reoxidation of Mo~(5+).     

胺铜或镍配离子的TCNQ电荷转移盐的合成和物理性质

合成了七个胺铜或镍配离子的TCNQ电荷转移盐[ML2][TCNQ]n(TCNQ=7, 7, 8, 8-四氰基对苯二醌二甲烷; n=2, 3;M=Cu, Ni; L=tn, pn, dien, dmtade)。通过元素分析、红外光谱、电子光谱、顺磁共振谱、光电子能谱、磁化率和电导率对这些电荷转移盐进行了表征。结果表明, 这些电荷转移盐分子中存在TCNQ^0和TCNQ^-且TCNQ^0与TCNQ^-之间存在相互作用, 部分电荷从[TCNQ]n^2向[ML2]^2^+转移, 导致化合物中的金属表现为混合价态。七个样品的室温电导率在10^-^5～10^-^1^0S.cm^-^1, 属于有机半导体, 其导电性主要归结为一维TCNQ分子柱的形成。     

Hydrothermal syntheses and characterizations of two new hydrogen bond-supported supramolecular compounds based on polyoxometalates

Two new polyoxometalates [HN(C₂H₅)₃]₃[PMo₁₂O₄₀] (1) and [NH₂(C₂H₄NH₃)₂]₂[Mo₅P₂O₂₃] (2) have been hydrothermally synthesized and characterized by IR, UV-Vis, XPS spectra, TG analyses, and single crystal X-ray diffraction. Crystal data for 1: monoclinic, space group C2/c, a = 24.651(5) Å, b = 10.822(2) Å, c = 22.413(5) Å, β = 120.37(3)°, and V = 5158.7(18) ų; for 2: triclinic, space group P-1, a = 9.821(2) Å, b = 9.948(2) Å, c = 14.687(3) Å, α = 95.490(3)°, β = 98.870(3)°, γ = 95.710(3)°, and V = 1401.7(5) ų. The crystal structure analyses reveal complex hydrogen bonds in both 1 and 2 in 3-D supramolecular arrays constructed from different polyoxoanions and organic ligands.     

Synthesis, characterization, and reactivity of Ti(IV)-monosubstituted Keggin polyoxometalates

Ti(IV)-monosubstituted Keggin-type polyoxometalates (Ti-POMs), mu-oxo dimer [Bu4N]8[(PTiW11O39)2O] (1), and three monomers [Bu4N]4[PTi(L)W11O39], where L = OH (2), OMe (3), and OAr (4, ArOH = 2,3,6-trimethylphenol (TMP)), have been prepared starting from mu-hydroxo dimer [Bu4N]7[(PTiW11O39)2OH] (5) or heteropolyacid H5PW11TiO40 or both. The compounds have been characterized by elemental analysis, IR, UV-vis, and multinuclear (31P, 1H, 183W) NMR. The interaction of 1 and 3-5 with H2O in MeCN produces 2. The hydrolysis constants, estimated from 31P and 1H NMR data, are 0.006 and 0.04 for 1 and 3, respectively. Studies by 31P NMR, IR, potentiometric titration, and cyclic voltammetry revealed that 1-3 and 5 afford the same protonated titanium peroxo complex [Bu4N]4[HPTi(O2)W11O39] (I) upon interaction with aqueous H2O2 in MeCN. The rates of formation of I correlate with the rates of hydrolysis of the Ti-POMs and follow the order of 5 > 1 > 3. A two-step mechanism of the reaction of Ti-POMs with H2O2, which involves hydrolysis of the Ti-L bonds to yield 2 followed by fast interaction of 2 with hydrogen peroxide producing I, is suggested. The equilibrium constant for the reaction of 2 with H2O2 to yield I and H2O, estimated using 31P NMR, is 10. The interaction of the Ti-POMs with TMP follows the trends similar to their interaction with H2O) and requires preliminary hydrolysis of the Ti-L bonds. All of the Ti-POMs catalyze the oxidation of TMP with H2O2 in MeCN to give 2,3,5-trimethyl-p-benzoquinone and 2,2',3,3',5,5'-hexamethyl-4,4'-biphenol. The product distribution is similar for all of the Ti-POMs. The catalytic activities of the Ti-POMs correlate with the rates of formation of I and follow the order of 2 > 5 > 1 > 3. The findings lay a basis for a better understanding of the nature of the reactivity of titanium in Ti-catalyzed oxidations.     

Structural characterization of mono-ruthenium substituted Keggin-type silicotungstates

We have synthesized the mono-ruthenium substituted Keggin-type silicotungstate [SiW(11)O(39)Ru(III)(H(2)O)](5-) (1a) by reaction of the mono-lacunary silicotungstate precursor [SiW(11)O(39)](8-) with Ru(acac)(3) under hydrothermal conditions and isolated as the caesium salt Cs(5)[SiW(11)O(39)Ru(III)(H(2)O)] (1). The DMSO-coordinated complex [SiW(11)O(39)Ru(III)(DMSO)](5-) (2a) was prepared by reaction of 1a with DMSO in aqueous solution at 353 K and isolated as the caesium-potassium mixed salt Cs(4.9)K(0.1)[SiW(11)O(39)Ru(III)(DMSO)] (2). Both compounds 1 and 2 were characterized by single-crystal X-ray structure analysis, powder X-ray structure analysis, UV-Vis spectroscopy, cyclic voltammetry, IR-spectroscopy and elemental analysis. 1 crystallized in the tetragonal space group P4(2)/ncm with a = 20.9299(4), c = 10.3603(4) Angstrom, Z = 4. The ruthenium atom in the Keggin unit could not be distinguished from the tungsten due to disorder. The structural analysis of 2 (monoclinic, P2(1)/c, a = 13.5850(4), b = 20.2764(7), c = 18.1326(4) Angstrom, beta = 90.8730(10) degrees , Z = 4) successfully revealed that the incorporated ruthenium atom is coordinated by DMSO through a Ru-S bond. Polyanion 2a represents the first mono-substituted Keggin ion in which the ruthenium center is not crystallographically disordered. UV-Vis spectroscopy combined with controlled potential electrolysis confirmed that the incorporated rutheniums in 1 and 2 have a valence state of +3. The IR spectra of both 1 and 2 were very similar. All these data indicate that 1 synthesized by reaction of the mono-lacunary silicotungstate K(8)[SiW(11)O(39)] with Ru(acac)(3) under hydrothermal conditions is truly the mono-ruthenium substituted Keggin-type silicotungstate.