Two novel nickel cluster substituted polyoxometalates: Syntheses, structures and their photocatalytic activities, magnetic behaviors, and proton conduction properties

Two novel nickel cluster substituted polyoxometalates (POMs), H7Na19(H2O)26{Ni12(OH)9(PO4)4(A-α-SiW9O34)[W4O10(OH)(PO2(OH)2)2(A-α-SiW9O34)2]}·4C2H8N·27H2O (1) and H26.5K2.5Na(H2O)16[Ni6(OH)(BO3)2(dien)2(B-α-SiW10O37)2]2·24H2O (2) (dien = diethylenetriamine), have been successfully prepared. 1 is a Ni12-substituted POM comprised of a novel {Ni12(OH)9(PO4)4} core, an A-α-{SiW9O34} unit and an uncommon {W4O10(OH)[PO2(OH)2]2(A-α-SiW9O34)2} fragment. 2 is a Ni6-substituted sandwich-type POM constructed from two B-α-{SiW10O37} units and an unusual boat-like {Ni6(OH)(BO3)2(dien)2} cluster. Photocatalytic study reveals that 2 shows a moderate catalytic activity in visible-light-driven CO2 reduction reactions. Additionally, the magnetic behaviors and the proton conduction performances of the compounds were investigated.