Synthesis and photo-/electro-catalytic properties of Keggin polyoxometalate inorganic–organic hybrid layers based on d10 metal and rigid benzo-diazole/-triazole ligands†
Abstract
Herein, five Keggin polyanion-templated inorganic–organic hybrids, (H3biz)4[SiMo12O40] (1), (H3biz)3(H2biz)[PMo12O40] (2), [{Cu7(Hbtz)2(btz)4}{PMo12O40}] (3), [{Ag7(Hbtz)2(btz)4}{AsW12O40}] (4), and [{Ag9(H2biz)2(biz)4} {H2PW12O40}] (5) (H2biz = 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 H2biz 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 {M7(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 {Ag9(biz)4(H3biz)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 CuI/AgI–π interactions and π–π 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.