The 9-cobalt(II)-containing trimeric, cyclic polyanion [Co 9 (OH) 3 (H 2 O) 6 (PO 4) 2 (B-α-GeW 9 O 34) 3 ] 21− (1) was synthesized in an aqueous phosphate solution at pH 8 and isolated as a hydrated mixed sodium−cesium salt. Polyanion 1 was structurally and compositionally characterized in the solid state by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, as well as thermogravimetric and elemental analyses. The magnetic and electrochemical properties of 1 were also studied and compared with those of its phosphorus analogue, [Co 9 (OH) 3 (H 2 O) 6 (HPO 4) 2 (B-α-PW 9 O 34) 3 ] 16− (Co 9-P). The electrochemical water oxidation activity of the cesium salt of 1 under heterogeneous conditions was also studied and shown to be superior to that of Co 9-P. The experimental results were supported by computational studies.
Two novel organic-inorganic hybrid tungsto- and molybdo-telurates having formula [{Na(4)(H(2)O)(14)}{Cu(gly)}(2)][TeMo(6)O(24)] (1){gly = glycine} and [{Cu(en)(2)}(3){TeW(6)O(24)}]·6H(2)O {en = ethyline-diamine} (2) based on Anderson type heteropolyoxometalates (POMs) have been synthesized and characterized by X-ray crystallography. Common structural feature of both 1 and 2 is the presence of a unique 1D open rack-like architecture, where the disc shaped Anderson POMs act as steps and cationic Cu-organic complexes act as handles of the rack. In 1 the independent structural unit is a 1D coordination polymer with the above mentioned rack type architecture, while in 2, these independent rack-like architectures are further extended to a 2D coordination polymer. Heterogeneous catalysis for the epoxidation of cyclohexene and styrene by complexes 1 and 2 showed very good catalytic efficiency resulting epoxides of ~60% yield, with dialcohol formed by the hydrolysis of epoxides, as the other major product (~28%). Cyclic voltammetric studies of [{Na(4)(H(2)O)(14)}{Cu(gly)}(2)][TeMo(6)O(24)] (1) in aqueous KCl solution indicates that the redox changes occur only on the copper centers and supported by carrying out parallel experiments on the precursors like ([Cu(gly)(2)](2+) and [TeMo(6)O(24)](6-), under the identical experimental conditions. The E(1/2) = 0.662, -0.142 and -0.332 V(vs. SCE) correspond to Cu(III) → Cu(II), Cu(II) → Cu(I) and Cu(I) → Cu(0) reductions, respectively. Thermal analyses reveal identical phase transition reactions with an exothermic peak in the DTA curve at 380 °C for 1 and an endothermic peak appears at comparatively higher temperature (408 °C) for 2 manifesting the higher stability of tungstane based POM over the molybdenum ones. EPR as well as magnetic moment results indicate that both the complexes 1 and 2 are paramagnetic with one unpaired electron per copper(II) ion.
A novel bis(glycinato)copper(II)paradodecatungstate Na 8 [{Cu(gly) 2 } 2 ]-{H 2 (H 2 W 12 O 42 )}] Á 24H 2 O (1) has been synthesized under hydrothermal conditions. The crystal structure of 1 reveals an infinite one-dimensional chain along the [100] direction and is built from paradodecatungstate (H 2 W 12 O 42 ) 10-clusters joined through [Cu(gly) 2 ] moieties. Parallel chains are interlinked by NaO 6 octahedra to generate a two-dimensional network.
6 pagesInternational audienceA mixed-valent manganese tricapped Keggin polyoxometalate(3) has been designed by insertion of three Mn atoms from [MnIIMnIII 2(μ3-O)(2-Cl benzoato)6(py)3] (1) into the vacant sites of the trilacunary precursor Na10[A-!-SiW9O34] (2). This compound exhibits strong antiferromagnetic interaction between the spin carriers of the Mn mixedvalent trinuclear moiety, which suggests an S = 5/2 ground state
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.