Assembly of Polyoxometalate-Based Metal–Organic Frameworks with Silver(I)-Schiff Base Coordination Polymeric Chains as Building Blocks

Six crystalline polyoxometalate-based three-dimensional (3D) metal–organic frameworks {[AgL4(DMF)]­[AgL4]2(PMo12O40)·DMF·3H2O}n (1), {[AgL4]3(PW12O40)·6H2O}n (2), {[AgL5]3(PMo12O40)·(CH3CN)3}n (3), {[AgL5(PW12O40)]­[AgL5(H2O)0.25(MeOH)0.25)]­[AgL5]0.5·DMF·(H2O)1.5}n (4), {[AgL6]3(PMo12O40)·DMF·H2O}n (5), and {[AgL7]3(PMo12O40)·DMF·(CH3CN)3}n (6) have been successfully synthesized based on one-dimensional (1D) coordination polymers constructed by the coordination of polydentate Schiff-base ligands and silver cations and saturated α-Keggin polyoxoanion [PM12O40]3– (M = W, Mo) as building blocks, where L4, L5, L6, and L7 are 2,5-bis­(3-pyridyl)-3,4-diaza-2,4-hexadiene, 1,4-bis­(3-pyridyl)-2,3-diaza-1,3-butadiene, 2,5-bis­(4-pyridyl)-3,4-diaza-2,4-hexadiene, and 1,4-bis­(4-pyridyl)-2,3-diaza-1,3-butadiene, respectively. Compounds 1–6 are structurally characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses (TG), powder X-ray diffraction (XRD), and complete single-crystal X-ray diffraction analyses. The structures of 1–6 exhibit 3D supramolecular networks formed by linking 1D Ag-Schiff base chains and α-Keggin polyoxoanion units through the cooperativity of multiform supramolecular interactions, such as intermolecular Ag···O weak interactions, Ag···π interactions, π···π interactions, and hydrogen bonds. The photoluminescent properties of 1–6 have been investigated in the solid state.