Imidazole coordinated sandwich-type antimony poly-oxotungstates Na9[{Na(H2O)2}3{M(C3H4N2)}3(SbW9O33)2]•xH2O (M=NiII, CoII, ZnII, MnII)

The imidazole covalently coordinated sandwich-type heteropolytungstates Na-9[{Na(H2O)(2)}(3) {M(C3H4N2)}(3)-(SbW9O33)(2)]center dot xH(2)O (M=Ni-II, x=32; M=Co-II, x=32; M=Zn-II, x=33; M=Mn-II, x=34) were obtained by the reaction of Na2WO4 center dot 2H(2)O, SbCl3 center dot 6H(2)O, NiCl2 center dot 6H(2)O [MnSO4-H2O, Co(NO3)(2)center dot 6H(2)O, ZnSO4 center dot 7H(2)O] and imidazole at pH approximate to 7.5. The structure of Nag[{Na(H2O)(2)}(3) {Ni(C3H4N2)}(3)(SbW9O33)(2)]center dot 32H(2)O was determined by single crystal X-ray diffraction. Polyanion [{Na(H2O)(2)}(3) {Ni(C3H4N2)}(3)(SbW9O33)(2)}(3)](9-) has approximate C-3v, symmetry, imidazole coordinated six-nuclear cluster [{Na(H2O)(2)}(3) {Ni(C3H4N2)}(3)](9+) is encapsulated between two (alpha-SbW9O33)(9-), the three rings of imidazole in the polyanion are perpendicular to the horizontal plane formed by six metals (Na-Ni-Na-Ni-Na-Ni) in the central belt, and pi-stacking interactions exist between imidazoles of neighboring polyanions with dihedral angel of 60 degrees. The compounds were also characterized by IR, UV-Vis spectra, TG and DSC, and the thermal decomposition mechanism of the four compounds was suggested by TG curves.