Hydrothermal synthesis and crystal structural characterization of two new modified polyoxometalates constructed of positive and negative metal–oxo cluster ions

Two new interesting polyoxometalate derivatives f½Nið2; 20-bipyÞ2H2O 2½MoV3 MoVI 5 VIV 8 O40ðPO4Þ gf½Nið2; 20-bipyÞ2H2O 2½MoV3 MoVI 5 VIV 8 O40ðPO4Þ g$5H2O 1 and f½Coð2; 20-bipyÞ2H2O 4½MoV4 MoVI 4 VIV 8 O40ðPO4Þ gf½Coð2; 20-bipyÞ2H2O 2½MoV3 MoVI 5 VIV 8 O40ðPO4Þ gðH3OÞ$4H2O 2 constructed of modified metal–oxo cluster ions carrying positive and negative changes, respectively, was hydrothermally prepared and structurally characterized by IR, ESR, XPS, elemental analysis and X-ray crystallography. The result of structure determination shows that compound 1 and 2 are isostructural and both contain polyoxocation and polyoxoanion, and both cation and anion are built on mixed Mo–V tetra-capped pseudo-Keggin units with P centre, [Mo8V8O40(PO4)]nK, bonded to four or two [Ni(2,20-bipy)2H2O]2C complexes, respectively, via terminal oxygen of the capping V atoms. Magnetism measurement indicates that there exists antiferromagnetic interaction in complex 1 and 2. q 2005 Elsevier B.V. All rights reserved