Synthesis and photo-/electro-catalytic properties of Keggin polyoxometalate inorganic-organic hybrid layers based on d10 metal and rigid benzo-diazole/-triazole ligands

Herein, five Keggin polyanion-templated inorganic-organic hybrids, (H(3)biz)(4)[SiMo12O40] (1), (H(3)biz)(3)(H(2)biz)[PMo12O40] (2), [{Cu-7(Hbtz)(2)(btz) 4}{PMo12O40}] (3), [{Ag-7(Hbtz)(2)(btz)(4)}{AsW12O40}] (4), and [{Ag-9(H(2)biz)(2)(biz)(4)} {H2PW12O40}] (5) (H(2)biz = benzimidazole, Hbtz = benzotriazole) were hydrothermally synthesized and characterized via elemental analysis, thermogravimetry (TG), infrared spectroscopy (IR), ultraviolet spectroscopy (UV), and single-crystal X-ray diffraction. A remarkable aspect of compound 1 is that six pairs of H(2)biz ligands are circularly arranged around the {SiMo12} cluster; this leads to the formation of a unique 2-D supramolecular layer. The most prominent feature of the structure of compound 2 is that protonated Hbiz ligands link the {PMo12} cluster into hexagonal units, which are further extended into a 2-D supramolecular array via edge-sharing modes. The Keggin {PMo12} and {AsW12} clusters in compound 3 and 4 are first extended into octa-connected 2-D sheets by the unusual heptanuclear complex {M-7(Hbtz)(2)(btz)(4)} (M = Cu for 3 and Ag for 4) linker. Interestingly, two types of M-M interactions exist in the heptanuclear units. Compound 5 exhibits an unprecedented 2D network constructed from nine-nuclear silver complex {Ag-9(biz)(4)(H(3)biz)(2)} bridges and {PW12} clusters. Most strikingly, carbene silver and the coexistence of multiple Ag-C bonds are first observed in the nine-nuclear unit. Intensive Cu-I/Ag-I-pi interactions and pi-pi stacking play important roles in the packing arrangements of 3-5. Additionally, the electrochemical, electrocatalytic, fluorescence, and photocatalytic properties of 1-5 have been investigated in detail.