Assembly of Mn-Containing Unprecedented Selenotungstate Clusters with Photocatalytic H2 Evolution Activity

The reaction of Na2WO4 and Na2SeO3 in the presence of MnCl2 under moderately acidic conditions yielded two unprecedented tungstoselenites dimeric K2Na10[K-2 subset of{MnSe4W23O85(H2O)(6)}]center dot 29H(2)O (4) and trimeric wheel-shaped K2Na10[K-2 subset of{Mn3Se7W39O131(OH)(20)(H2O)(2)}]center dot 60H(2)O (2). The assemblies of 1 and 2 are based upon the structure directing effects of Sew heteroatoms for generating diverse well-defined vacancy selenotungstate precursors during the formation. The polyoxoanion of 1 contains two novel Wells-Dawson-type-like {Se2W11} fragments, which are constructed from novel {SeW4} and {SeW7} species derived from Wells-Dawson-type {alpha-Se2W14} fragments and one disorder of Mn/W center. The polyoxoanion of 2 exhibits a crown-type structure composed of a [Se6W38O120(OH)(18)(H2O)(2)](6-) "host" (abbreviated as {Se6W38}) encapsulating SeO32--modified Mn/W and two K+ "guests". Remarkably, the crown {Se6W38} shell remains a new type of {Se2W12}-based trimeric aggregate in the polyoxometalates chemistry. The two,compounds were characterized by single-crystal X-ray structure analysis, IR spectroscopy, thermogravimetric, UV/vis spectroscopy, and ESI-MS. Moreover, their photo catalytic H-2 evolution activity was also investigated.