Search

Two new Keggin- and Wells-Dawson-type polyoxometalate-based organic–inorganic hybrid copper–organonitrogen complexes have been synthesized under hydrothermal conditions: [CuI(4,4′-bpy)]2[H2SiW12O40] ⋅ 2H2O (4,4′-bpy = 4,4′-bipyridine) (1) and (en =ethylenediamine), and characterized by elemental analysis, IR spectra, TGA, XRD, and single crystal X-ray diffraction. In 1, [Cu(4,4′-bpy)]+ cations form polymeric chains and a weak Cu–O linkage makes the anions situate between two chains, forming an infinite 1-D ladder-chain structure. Such 1-D ladder-chains are further interconnected via hydrogen bonding into a 3-D supramolecular framework. Compound 2 with covalently bonded 3-D structure consists of saturated Wells-Dawson tungstoarsenate polyoxoanions and copper complexes with two types (rigid and flexible) of ligands. The polyoxoanion has the highest connectivity for Wells-Dawson tungstoarsenate polyoxoanion coordination polymers to date. XPS spectra indicate that three W atoms in the Dawson unit were reduced...

Three neutral polyoxometalates [PVW11O40{M(phen)2H2O}2] · 3H2O (phen = 1,10′-phenanthroline, M=Co 1, Zn 2, Ni 3) are composed of water and the neutral Keggin-type polyoxometallate covalently linking a pair of transition metal complex fragments on opposite sides. The transition metal lies in the center of a distorted octahedron. Multi hydrogen-bonding interactions between coordinated waters of neutral polyoxometalate molecules and terminal oxygen atoms of Keggin units and between bridging oxygens of Keggin units and lattice water create a two dimensional layer and between the layers there exist van der Waals forces. The framework of the neutral molecule begins to decompose at ca 500°C. Compound 1 exhibits a weak antiferromagnetic interaction in the 2–300 K range.

An inorganic-organic hybrid compound {[Cu(phen)3]2PW11VO40 · 2H2O (1) has been hydrothermally prepared and structurally characterized by elemental analyses, IR, CV, TG, magnetic susceptibility measurements and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group C2/c with a = 27.232(2) A, b = 25.351(2) A, c = 16.2748 (4) A, β = 105.20°, V = 10842.3 A3, Z = 4, R1 = 0.0490 and wR2 = 0.1362. The structure of 1 exhibits a three-dimensional supramolecular network, formed by hydrogen-bonding and π–π stacking interactions. The three-dimensional network consists of one-dimensional honeycomb channels, which accommodate free water molecules. The size of the channel is 10.4 × 10.4 A. Electrochemistry of 1 shows it undergoes three one-electron reversible redox processes. Variable-temperature magnetic measurements show typical antiferromagnetic interactions in the 2–300 K temperature range.

A new neutral α-Keggin polyoxometalate, [{Cu(phen)2}2SiW12O40] (1) (phen = 1,10-phenanthroline) was hydrothermally synthesized and characterized by IR, TG and single-crystal X-ray diffraction. The compound is monoclinic, space group P21/c with a = 26.065(5), b = 11.867(2), c = 23.385(5) A, β = 113.78(3)°, V = 6619 A3, Z = 4. X-ray analysis showed that both [Cu(phen)2]2+ units are supported on the α-Keggin polyoxoanion [SiW12O40]4− via the surface bridging and terminal oxygen atoms of two non-adjacent WO6 octahedra; these show unusual coordination environments. One Cu ion displays distorted trigonal bipyramidal geometry and the other square pyramidal. The unusual coexistence of complexes with different geometries is most likely caused by steric effects involving surface oxygen atoms of the heteropolytungstate and phen, which prevent the presence of a sixth coordinating atom. Weak π–π stacking interactions between phen groups give a 1D chain-like structure and hydrogen bonds are responsible for extended 2D ...