Photocatalysis from a series of polyoxoazocobaltate high-nuclearity nanoclusters

Three {Co-20} nanoclusters possessing photocatalytic activity, namely, [Co-20(OH)(24)(MMT)(12)(SO4)](NO3)(2)center dot 6H(2)O (1), [Co-20(MT)(12)(mu(3)-OH)(23)(mu(3)-O)(SO4)(CH3O)]center dot 2EtOH (2) and [Co-20(AMT)(11)(MT)(mu(3)-OH)(22)(mu(3)-O)(2)(SO4)(H2O)]center dot EtOH center dot 4H(2)O (3) (MMT = 2-mercapto-5-methyl-1,3,4-thiadiazole, MT = 2-mercapto-1,3,4-thiadiazole, AMT = amino-5-mercapto-1,3,4-thiaoldiaze and EtOH = ethanol) have been obtained under hydrothermal conditions. Compound 1 presents a homometallic Co-II cluster containing the alpha-Keggin polyoxometalate structure. Compound 2 features a cobalt cluster including the alpha-Keggin-type polyoxoazocobaltate {Co-12} core, capped by seven octahedral CoII ions and one square-pyramidal Co-II ion. Different from compounds 1 and 2, compound 3 possesses the semi-open square-pyramidal-based {Co-10} core, and ten octahedral Co-II ions are distributed around the core cluster. Through the comparison from structures of compound 1 and compounds 2-3, the different substituent groups of the organic ligands play an important role in the formation of the final homometallic Co-II clusters. The electrochemical behaviors of the title compounds at room temperature have been investigated. Moreover, the high-nuclearity metal clusters are firstly acted as photocatalysts to be researched, and then the photocatalytic properties show that compounds 1-3 as the potential photoactive materials have the selectivity for degradation of some organic dyes.