Studies on electron transfer reactions: reduction of heteropoly 11-tungstophosphovanadate(V) by <Emphasis Type="SmallCaps">l</Emphasis>-cysteine and thioglycolic acid in aqueous acid medium

The rates of the electron transfer reaction of l-cysteine and thioglycolic acid with the polyoxometalate, [PV^VW₁₁O₄₀]⁴⁻, have been measured spectrophotometrically in aqueous acid medium. The polyoxometalate oxidizes cysteine to cystine and thioglycolic acid to dithioglycolic acid and gets reduced to heteropoly blue, [PV^IVW₁₁O₄₀]⁵⁻. The order of the reaction with respect to oxidant is one, whereas the reaction shows second order dependence on the substrates. The rate–pH profile shows that both the unionized and ionized thiol groups of the substrates are active species involved in electron transfer. A suitable mechanism has been proposed for the title reaction based on the results of kinetic studies.     

Studies on electron transfer reactions: oxidation of phenol and ring-substituted phenols by heteropoly 11-tungstophosphovanadate(V) in aqueous acidic medium

The kinetics of oxidation of phenol and a few ring-substituted phenols by heteropoly 11-tungstophosphovanadate(V), [PV^VW₁₁O₄₀]⁴⁻ (HPA) have been studied spectrophotometrically in aqueous acidic medium containing perchloric acid and also in acetate buffers of several pH values at 25 °C. EPR and optical studies show that HPA is reduced to the one-electron reduced heteropoly blue (HPB) [PV^IVW₁₁O₄₀]⁵⁻. In acetate buffers, the build up and decay of the intermediate biphenoquinone show the generation of phenoxyl radical (ArO^·) in the rate-determining step. At constant pH, the reaction shows simple second-order kinetics with first-order dependence of rate on both [ArOH] and [HPA]. At constant [ArOH], the rate of the reaction increases with increase in pH. The plot of apparent second-order rate constant, k ₂, versus 1/[H⁺] is linear with finite intercept. This shows that both the undissociated phenol (ArOH) and the phenoxide ion (ArO⁻) are the reactive species. The ArO⁻–HPA reaction is the dominant pathway in acetate buffer and it proceeds through the OH⁻ ion triggered sequential proton transfer followed by electron transfer (PT-ET) mechanism. The rate constant for ArO⁻–HPA reaction, calculated using Marcus theory, agrees fairly well with the experimental value. The reactivity of substituted phenoxide ions correlates with the Hammett σ⁺ constants, and ρ value was found to be −4.8. In acidic medium, ArOH is the reactive species. Retardation of rate for the oxidation of C₆H₅OD in D₂O indicates breaking of the O–H bond in the rate-limiting step. The results of kinetic studies show that the HPA-ArOH reaction proceeds through a concerted proton-coupled electron transfer mechanism in which water acts as proton acceptor (separated-CPET).     

Vanadium(V)-substituted Keggin-type heteropolyoxotungstophosphates as electron transfer and antimicrobial agents: oxidation of glutathione and sensitization of MRSA towards β-lactam antibiotics

Glutathione (GSH) undergoes facile electron transfer with vanadium(V)-substituted Keggin-type heteropolyoxometalates, [ \textPV^\textV \textW _{1 1} \textO _{4 0} ] ^{4 -} [ {\text{PV}}^{\text{V}} {\text{W}}_{ 1 1} {\text{O}}_{ 4 0} ]^{{ 4 { - }}} (HPA1) and [ \textPV^\textV \textV^\textV \textW _{1 0} \textO _{4 0} ] ^{5 -} [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} ]^{{ 5 { - }}} (HPA2). The kinetics of these reactions have been investigated in phthalate buffers spectrophotometrically at 25 °C in aqueous medium. One mole of HPA1 consumes one mole of GSH and the product is the one-electron reduced heteropoly blue, [ \textPV^\textIV \textW _{1 1} \textO ₄₀ ] ^5- [ {\text{PV}}^{\text{IV}} {\text{W}}_{ 1 1} {\text{O}}_{ 40} ]^{ 5- } . But in the GSH-HPA2 reaction, one mole of HPA2 consumes two moles of GSH and gives the two-electron reduced heteropoly blue [ \textPV^\textIV \textV^\textIV \textW ₁₀ \textO ₄₀ ] ^7- [ {\text{PV}}^{\text{IV}} {\text{V}}^{\text{IV}} {\text{W}}_{ 10} {\text{O}}_{ 40} ]^{ 7- } . Both reactions show overall third-order kinetics. At constant pH, the order with respect to both [HPA] species is one and order with respect to [GSH] is two. At constant [GSH], the rate shows inverse dependence on [H⁺], suggesting participation of the deprotonated thiol group of GSH in the reaction. A suitable mechanism has been proposed and a rate law for the title reaction is derived. The antimicrobial activities of HPA1, HPA2 and [ \textPV^\textV \textV^\textV \textV^\textV \textW ₉ \textO _{4 0} ] ^{6 -} [ {\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 9} {\text{O}}_{ 4 0} ]^{{ 6 { - }}} (HPA3) against MRSA were tested in vitro in combination with vancomycin and penicillin G. The HPAs sensitize MRSA towards penicillin G.     

Synthesis and spectral properties of titanium(iv) polynuclear hydroxo complexes stabilized in solution by the [PW11O39]7− heteropolyanion

Unsaturated heteropolyanions (HPA) [PW₁₁O₃₉]⁷⁻ stabilize Ti^IV hydroxo complexes in aqueous solutions (Ti: PW₁₁ [PW₁₁O₃₉]⁷⁻⪯12, pH 1–3). Spectral studies (optical,¹⁷O and³¹P NMR, and IR spectra) and studies by the differential dissolution method demonstrated that Ti^IV hydroxo complexes are stabilized through interactions of polynuclear Ti^IV hydroxo cations with heteropolyanions [PW₁₁TiO₄₀ ⁵⁻ formed. Depending on the reaction conditions, hydroxo cations Ti _n−1O _x H _y ^m+ either add to oxygen atoms of the W−O−Ti bridges of the heteropolyanions to form the complex [PW₁₁TiO₄₀·Ti _n−1O _x H _y ] ^k− (at [HPA]=0.01 mol L⁻¹) or interact with Ti^IV of the heteropolyanions through the terminal o atom to give the polynuclear complexes [PW₁₁O₃₉Ti−O−Ti _n−1O _x H _y ]^q− (at [HPA]=0.2 mol L⁻¹). When the complexes of the first type were treated with H₂O₂, Ti^IV ions added peroxo groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–920, May, 1997.     

Stabilization of uranium(IV) in heteropoly anions*

Summary The heteropoly anions [U^IVMo₁₂O₄₂]^8–(UMo₁₂), [U^IVW₁₀O₃₆]^8– (UW₁₀), [U^IV(PW₁₁O₃₉)₂]¹⁰ [U(PW₁₁)₂] and [U^IV(SiW₁₁O₃₉)₂]¹² [U(SiW₁₁)₂] were examined by cyclic voltammetry on a wax-impregnated carbon electrode. Reversible one-electron oxidations were observed for UMo₁₂ (E = +0.91 V vs see at pH = ca. 0), U(PW₁₁ )2 (E = +0.60 V at pH 4.4) and U(SiW₁₁)₂ (E = +0.19 V at pH 4.4). No oxidation of UW₁₀ was detected at potentials prior to oxygen discharge (ca. +0.9 V at pH 7). Controlled potential oxidation of aqueous solutions of UMo₁₂ gave unstable solutions of [U^VMo₁₂O₄₂]^7–. Oxidation of U(PW₁₁)2 was achieved in aqueous and nonaqueous (acetonitrile, propylene carbonate) solution. The electronic spectra of U^VMo₁₂ and U^V(PW₁₁)₂ are reported and are discussed in terms of UO₁₂ (/y) and UO₈ (D4d) chromophores respectively. Possibilities for geometrical and optical isomers of U(XW 11)2 anions are considered. Solutions of brucinium salts of U(PWI I)2 and UW₁₀ in dimethyl formamide show induced Cotton effects at wavelengths corresponding to the f-f transitions of UIV. The voltammograms of UMo₁₂, ThMo₁₂ and CeMo₁₂ show an irreversible twelve-electron reduction at -0.25 V. The pale brown reduced solutions cannot be reoxidized to the original heteropoly anions.Taken from the Ph. D. Thesis of S.C.T., Georgetown University, 1977. Presented in part at the 17th International Conference on Coordination Chemistry, Hamburg, September 1976.     

High‐Field Pulsed EPR Spectroscopy for the Speciation of the Reduced [PV2Mo10O40]6− Polyoxometalate Catalyst Used in Electron‐Transfer Oxidations

An in‐depth spectroscopic EPR investigation of a key intermediate, formally notated as [PV^IVV^VMo₁₀O₄₀]^6? and formed in known electron‐transfer and electron‐transfer/oxygen‐transfer reactions catalyzed by H₅PV₂Mo₁₀O₄₀, has been carried out. Pulsed EPR spectroscopy have been utilized: specifically, W‐band electron–electron double resonance (ELDOR)‐detected NMR and two‐dimensional (2D) hyperfine sub‐level correlation (HYSCORE) measurements, which resolved ⁹⁵Mo and ¹⁷O hyperfine interactions, and electron–nuclear double resonance (ENDOR), which gave the weak ⁵¹V and ³¹P interactions. In this way, two paramagnetic species related to [PV^IVV^VMo₁₀O₄₀]^6? were identified. The first species (30–35 %) has a vanadyl (VO²⁺)‐like EPR spectrum and is not situated within the polyoxometalate cluster. Here the VO²⁺ was suggested to be supported on the Keggin cluster and can be represented as an ion pair, [PV^VMo₁₀O₃₉]^8?[V^IVO²⁺]. This species originates from the parent H₅PV₂Mo₁₀O₄₀ in which the vanadium atoms are nearest neighbors and it is suggested that this isomer is more likely to be reactive in electron‐transfer/oxygen‐transfer reaction oxidation reactions. In the second (70–65 %) species, the V^IV remains embedded within the polyoxometalate framework and originates from reduction of distal H₅PV₂Mo₁₀O₄₀ isomers to yield an intact cluster, [PV^IVV^VMo₁₀O₄₀]^6?.     

Studies on electron transfer reactions: reduction of heteropoly 10-tungstodivanadophosphate by <Emphasis Type="SmallCaps">l</Emphasis>-cysteine in aqueous acid medium

l-cysteine undergoes facile electron transfer with heteropoly 10-tungstodivanadophosphate, [ \textPV^\textV \textV^\textV \textW _{1 0} \textO _{4 0} ]^{5 -} , \left[ {{\text{PV}}^{\text{V}} {\text{V}}^{\text{V}} {\text{W}}_{ 1 0} {\text{O}}_{ 4 0} } \right]^{5 - } , at ambient temperature in aqueous acid medium. The stoichiometric ratio of [cysteine]/[oxidant] is 2.0. The products of the reaction are cystine and two electron-reduced heteropoly blue, [PV^IVV^IVW₁₀O₄₀]⁷⁻. The rates of the electron transfer reaction were measured spectrophotometrically in acetate–acetic acid buffers at 25 °C. The orders of the reaction with respect to both [cysteine] and [oxidant] are unity, and the reaction exhibits simple second-order kinetics at constant pH. The pH-rate profile indicates the participation of deprotonated cysteine in the reaction. The reaction proceeds through an outer-sphere mechanism. For the dianion ⁻SCH₂CH(NH₃ ⁺)COO⁻, the rate constant for the cross electron transfer reaction is 96 M⁻¹s⁻¹ at 25 °C. The self-exchange rate constant for the ^- \textSCH₂ \textCH( \textNH₃ ⁺ )\textCOO ^- \mathord

Liquid phase benzylation of toluene using benzyl alcohol over iron promoted sulfated zirconia

Concentrated (0.2 M) aqueous solutions of HP-acids, such as H_3+x+mPV^IV _mV^V _x-mMo_12-xO₄₀ and their analogues with an excess VO²⁺ cation, are oxidized by dioxygen at 343 K and atmospheric pressure through intermediate active complexes (IAC) [H_x+m-1PV^IV _mV^V _x-mMo_12-xO₄₀ ^{4 -}] · [VO²⁺]_y · O₂, where m + y ≥ 3. The electron transfer to the coordinated O₂ molecule inside AC is the limiting stage at high m. At low m, the formation of IAC becomes the limiting stage that results in a sharp decrease in the oxidation rate. This revised version was published online in August 2006 with corrections to the Cover Date.     

Kinetics and mechanism of the oxidation of arenes in the presence of heteropoly acids and palladium(II) complexes supported on silica gel

Pd(II) complexes and twelfth-series heteropoly acids (HPA) H₉[PMo₆V₆O₄₀] and H₃[PMo₁₂O₄₀] supported on silica gel oxidize benzene and toluene at 95°C. The formation of methyldiphenylmethane in the oxidation of toluene on HPA/SiO₂ and (PdCl₂−HPA)/SiO₂ catalysts, KIE>1 for the toluene/toluene-d₈ pair, and greater rate for toluene than for benzene are in accord with a one-electron transfer mechanism. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 249–252, July–August, 1999.     

Hydrothermal syntheses, crystal structures, and properties of two polyoxometalates [Cd(2,2′-bpy)3]2[PMoVMoVI 11O40] and [H3PMo12O40]·3(4,4′-bpy)·4H2O

Two Keggin-type phosphododecamolybdate compounds [Cd(2,2′-bpy)₃]₂[PMo^VMo^VI ₁₁O₄₀] (1) and [H₃PMo₁₂O₄₀]·3(4,4′-bpy)·4H₂O (2) (bpy=bipyridine) were prepared by the hydrothermal method for the first time and characterized by elemental analyses, X-ray single-crystal diffraction, ESR spectra, and IR spectra, showing that compound 1 consists of a mixed valence Keggin polyanion [PMo^VMo^VI ₁₁O₄₀]⁴⁻ and two isolated coordinated cations [Cd(2,2′-bpy)₃]²⁺, while compound 2 is an intermolecular compound based on organic substrate 4,4′-bpy and heteropoly acid unit H₃PMo₁₂O₄₀. Furthermore, both the compounds show strong photoluminescence properties in the solid state at room temperature. The catalytic activities of the two compounds were also determined by the oxidation of benzaldehyde to benzoic acid using H₂O₂ as oxidant in a liquid–solid triphase system.     

Multisensor system for determination of polyoxometalates containing vanadium at its different oxidation states

The electronic tongue (ET) multisensor system has been employed for the detection of metal-oxygen cluster anions (polyoxometalates) containing vanadium (IV/V) atoms. Sensitivity of a variety of potentiometric chemical sensors with plasticized polyvinyl chloride and chalcogenide glass membranes was evaluated with respect to vanadyl/vanadate ions, decavanadate and a series of Keggin-type polyoxometalates (POM) such as α-[SiW₁₁V^IVO₄₀]⁶⁻, α-[SiW₁₁V^VO₄₀]⁵⁻, α-[BW₁₁V^IVO₄₀]⁷⁻, α-[BW₁₁V^VO₄₀]⁶⁻, α-[PW₁₁V^IVO₄₀]⁵⁻ and α-[PW_12−nV_n^VO₄₀]⁽³⁺ⁿ⁾⁻ (n = 1, 2, 3). Sensor's responses to vanadium complexes were evaluated in the pH range of 2.4-6.5 and a set of sensors appropriate for detecting a variety of vanadium species was selected. Such sensor array was able to distinguish different vanadium complexes allowing their simultaneous quantification in binary (V(IV)/V(V)) mixtures. The vanillyl alcohol oxidation with α-[SiW₁₁V^VO₄₀]⁵⁻ was monitored using ET to evaluate the capacity of proposed analytic system to detect simultaneously V(IV)/V(V) in POM under dynamic equilibrium. ET was demonstrated to be a promising tool for the discrimination and quantification of vanadium-containing POMs at different oxidation states. In particular, such a system could represent a significant interest for the mechanistic studies of redox reactions with POMs.     

A novel method of the synthesis of molybdovanadophosphoric heteropoly acid solutions

A novel eco-friendly method of the synthesis of aqueous solutions of the Keggintype Mo-V-P heteropoly acids H_3+x PV _x Mo_12−x O₄₀ (HPA-x) is proposed. At the first stage, V₂O₅ is dissolved in cooled H₂O₂ to form peroxyvanadic compounds, which spontaneously decompose to yield a H₆V₁₀O₂₈ solution. The latter is stabilized by the addition of H₃PO₄ to yield a H₉PV₁₄O₄₂ solution that is added to a boiling aqueous suspension of (H₃PO₄ + MoO₃). This suspension is gradually evaporated producing the HPA-x solution. This safe and practically wasteless method holds much promise for the preparation of HPA-x solutions with x = 2–6.     

Hydrothermal synthesis and characterization of two new bicapped Keggin heteropoly tungstovanadated derivatives

Two new heteropoly tungstovanadate derivatives, [Fe(phen)₃]₂[W_10.5V_4.5O₄₂]·3H₂O (1) and [Fe(phen)₃]₂[W₁₀V₅O₄₂].6H₂O (2) (phen=1,10′-phenanthroline), have been synthesized under hydrothermal conditions by using different starting materials, and characterized by elemental analysis, IR, ESR, XPS, TGA and single-crystal X-ray diffraction analysis. Crystal data for compound 1: C₇₂H₅₄Fe₂N₁₂O₄₅V_4.5W_10.5, monoclinic, space group C2/c, , , , β=99.882(8)°, V=10002(5) ų, Z=4; for compound 2, C₇₂H₆₀Fe₂N₁₂O₄₈V₅W₁₀, monoclinic, space group C2/c, a=30.246(6) Å, , c=25.329(5) Å, β=100.34(3)°, V=10483(4) ų, Z=4. The crystal structure analysis reveals that both polyoxoanions are decorated with the [Fe(phen)₃]²⁺ cations_, and that they have analogous structure to each other with slightly different packing modes of the polyoxoanions, [Fe(phen)₃]²⁺ cations and water molecules. They are further linked to form two-dimensional (2D) supramolecular networks through extensive hydrogen bonding.     

Magnetic properties of lanthanide salts of silicomolybdate heteropoly blues

Eighteen lanthanide salts of silicomolybdate heteropoly blues, LnH₃[SiMo₁₀ ^VIMo₂ ^VO₄₀] · nH₂O, Ln₂H₂-[SiMo₉ ^VIMo₂ ^VO₃₉Co(H₂O)] · nH₂O and Ln₂H₂[SiMo₉ ^VIMo₂ ^VO₃₉Ni(H₂O)] · nH₂O (Ln = La, Ce, Pr, Nd, Sm or Gd), were prepared by electrolytic reduction and characterized by elemental analyses, i.r. spectra, and electronic spectra. Their electronic and magnetic properties were studied by means of e.s.r., ²⁹Si-n.m.r., and magnetic measurements. The results show that these heteropoly blues retain the Keggin structure. The measured magnetic moment of the Ln³⁺ ion in LnH₃[SiMo₁₀ ^VIMo₂ ^VO₄₀] · nH₂O is smaller than the theoretical values, implying that the Ln³⁺ cation interacts with the heteropoly blue anion. An antiferromagnetic interaction involving the d electron of the Co²⁺ or Ni²⁺ transition metal ion occur in the substituted silicomolybdate heteropoly blues. The e.s.r. spectra show the extent of reduction electron localization at 77 K. The electron density on the Si atom in the heteropoly blue increases with increasing electronegativity of the transition element (Mo, Co, Ni).     

Synthesis,structures and electrochemical properties of four organic–inorganic hybrid polyoxometalates constructed from polyoxotungstate clusters and transition metal complexes

Four novel organic–inorganic hybrid compounds [Cu₅ ^I(4,4′-bpy)₃(2,2′-bpy)₄][BW₁₂O₄₀] · H₂O (1), [Ni_0.5(2,2′-bpy)_1.25][Ni(2,2′-bpy)₃][Ni(2,2′-bpy)₂(H₂O)(SiW₁₁^VIW^VO₄₀)] · 0.5H₂O (2), [H₂bpy]₂[Zn(2,2′-bpy)₃]₂[Si₂W₁₈O₆₂] · 1.5H₂O (3) and [Cu^II(2,2′-bpy)₂]₂[SiW₁₂O₄₀] · 2H₂O (4) (2,2′-bpy = 2,2′-bipyridine, 4,4′-bpy = 4,4′-bipyridine) have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, electrochemical measurements and single-crystal X-ray diffraction. Compound (1) is a novel [BW₁₂O₄₀]⁵⁻ polyoxoanion bisupported by copper(I) coordination cations with mixed 2,2′-bpy and 4,4′-bpy ligands. Compound (2) is constructed from the [SiW₁₁^VIW^VO₄₀]⁵⁻ polyoxoanions supported by [Ni(2,2′–bpy)₂]²⁺. Compound (3) is composed of a novel [Si₂W₁₈O₆₂]⁸⁻ cluster and [Zn(2,2′–bpy)₃]²⁺ complexes, which held together into a three-dimensional (3D) supramolecular network through hydrogen-bonding interactions. Compound (4) shows a 2D layer framework constructed from a bisupporting Keggin polyoxoanion cluster and [Cu(2,2′–bpy)₂]²⁺ coordination polymer fragments, resulting in 3D networks via supramolecular interactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Kinetics of the outer-sphere oxidation of thiourea by heteropoly-α<Subscript>2</Subscript>-17-tungsto-1-vanadodiphosphate anion

Kinetics of the oxidation of thiourea (tu) by heteropoly-α₂-17-tungsto-1-vanadodiphosphate anion, α₂-[P₂V^VW₁₇O₆₂]^7?, have been studied spectrophotometrically in aqueous acidic medium at 25 °C. At low pH (2.4–3.0), the neutral form of tu is the only reactive species. At higher pH (4.2–4.9), both neutral and deprotonated forms of tu participate in the reaction. The observed mixed-order kinetics suggest two parallel reactions: one in which the order in [tu] is unity, and a second in which it is two. In both cases, the order in [α₂-[P₂V^VW₁₇O₆₂]^7?] is unity. Based on the kinetic studies, a mechanism is proposed, in which a second-order proton-coupled electron transfer involving NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7? proceeds through a sequential electron transfer, followed by proton transfer such that the reaction is an “activation-controlled” outer-sphere electron transfer process. By applying the Marcus equation, the self-exchange rate constants for the couples \({\text{NH}}_{2} {\text{CSNH}}_{2}^{ \cdot + }\)/NH₂CSNH₂ and α₂-[P₂V^VW₁₇O₆₂]^7?/α₂-[P₂V^IVW₁₇O₆₂]^8? were evaluated.     

Oxonium derivatives of <Emphasis Type="Italic">closo</Emphasis>-decaborate in reactions with sulfur-containing nucleophiles

The reaction of the [B₁₀H₉O₂C₄H₈]⁻, [B₁₀H₉OC₄H₈]⁻, and [B₁₀H₉OC₅H₁₀]⁻ anions with negatively charged S-nucleophiles, such as SH⁻, SCN⁻, and S₂O₃ ²⁻, resulted in the ring opening of the cyclic substituent and the formation of derivatives with the terminal thiol, thiocyanate, and thiosulfate groups. The structures of the products were confirmed by the IR, mass, and ¹H, ¹¹B, and ¹³C NMR spectra.     

Alkylation of hydroquinone with isobutene catalyzed by heteropoly acids in a two-phase system

The liquid-phase C-alkylation of hidroquinone with isobutene catalyzed by heteropoly acids H₃PW₁₂O₄₀, H₆P₂W₁₈O₆₂ and H₆P₂W₂₁O₇₁ (HPA) under phase-transfer conditions in a two-phase system, including toluene (upper phase) and HPA dioxane etherate, HPA·xC₄H₈O₁₂·yH₂O, (lower phase) has been studied.     

Synthesis, characterization and studies on the third-order optical non-linearities of novel charge-transfer heteropoly complexes (C8H12N2)5H7PMo12O40 and (C8H12N2)3H3PMo12O40·5H2O

Summary Two novel charge-transfer (CT) heteropoly complexes, (C₈H₁₂N₂)₅H₇PMo₁₂O₄₀ (1) and (C₈H₁₂N₂)₃H₃-PMo₁₂O₄₀·5H₂O (2), prepared by reacting p-Me₂NC₆H₄NH₂ with the four-electron heteropoly blue H₇PMo₁₂O₄₀·12H₂O and heteropoly acid H₃PMo₁₂O₄₀· xH₂O, respectively, were characterized by elemental analysis, and u.v., i.r., XPS and e.s.r. spectroscopies. A sizable electron-transfer interaction occurs within the product molecules and the heteropoly anions retain their Keggin structure. Their third-order optical non-linearity coefficients were measured using the Z-scan technique at a concentration of 4.68 × 10⁻⁶ mol dm⁻³ for (1) and 2.79 × 10⁻⁶ mol dm⁻³ for (2), with I ₀ = 2.38 × 10¹³ w m⁻² and λ = 532nm. The |χ⁽³⁾| for (1) is 2.61 × 10⁻¹⁰ esu and |χ⁽³⁾| for (2) is 1.05 × 10⁻¹⁰ esu.