Inserting -(CH2)n- (n=2, 3, 4) Spacers into the Reactant Mercaptomethyltetrazole Ligand for Tuning the Multinuclear AgI Clusters in Keggin-Based Compounds

Four SiMo12O404- (SiMo12)-based compounds, namely, [Ag6Cl2(mmt)(4)(H4SiMo12O40)(H2O)(2)] (1), [Ag-4(bmte)(2)(H2O)(2)(SiMo12O4 (0))] (2), [Ag-4(bmtr)(2)(H2O)(2)(SiMo12O40)] (3), and [Ag-4(bmtb)(3)(SiMo12O40)] (4) (mmt = 1-methyl-5-mercapto-1,2,3,4-tetrazole, bmte = 1,2-bis(1-methyl-S-mercapto-1,2,3,4-tetrazole)ethane, bmtr 1,3-bis(1-methyl-5-mercapto-1,2,3,4-tetrazole)propane, bmtb = 1,4-bis(1-methyl-S-mercapto-1,2,3,4-tetrazole)butane), have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction analyses reveal that insertion of -(CH2)(n)- spacers into the reactant mmt ligand plays important roles in constructing multinuclear Ag-I clusters in the title compounds and tuning the formation of different multinuclear Ag-I clusters. In compound 1, the mmt ligands link Ag-I ions forming a three-dimensional non-multinuclear self-penetrating framework with large dimension channels occupied by SiMo12 polyanions. In 2, a tetranuclear [Ag-4(bmte)(2)(H2O)(2)](4+) and SiMo12 anions arrange alternately forming a one-dimensional (ID) chain. The structure of compound 3 is similar to that of 2, except for different coordination modes of Ag-I ions in tetranuclear clusters and SiMo12 polyanions owing to the longer -(CH2)(3-) alkyl skeleton of bmtr ligand. Compound 4 exhibits a two-dimensional grid layer formed by a ID Ag-I ribbon based on binuclear Ag-I clusters and bridging bmtb ligands with the longest -(CH2)(4)- alkyl skeleton. The SiMo12 polyanions as tetradentate inorganic linkages reside in the grids. The influences of -(CH2)(n)- spacers on forming and tuning different multinuclear Ag-I clusters have been discussed. Furthermore, the photochemical catalysis and electrochemical properties of the title compounds have been studied.