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)center dot DMF center dot 3H(2)O}(n) (1), {[AgL4]3(PW12O40)center dot 6H(2)O} (2), {[AgL5](3)(PMo12O40).(CH3CN)(3)}(n) (3), {[AgL5(PW12O40)][AgL5(H2O)(0.25)(MeOH)0.25)][AgL5](0.5)center dot DMF.(H2O)(1.5)}(n) (4), {[AgL6](3)(PMo12O40)center dot DMF center dot H2O} (5), and {[AgL7(PM12O40).DMF center dot(CH3CN)(3)}(n) (6) have been successfully synthesized based on one-dimensional (ID) coordination polymers constructed by the coordination of polydentate Schiff-base ligands and silver cations and saturated alpha-Keggin polyoxoanion [PM12O40](3-) (M = W, Mo) as building blocks, where L-4, L-5, L-6, and L-7 are 2,5-bis(3-pyridy1)-3,4-diaza-2,4-hexadiene, 1,4-bis(3-pyridy1)-2,3-diaza-1,3-butadiene, 2,5-bis(4-pyridy1)-3,4-diaza-2,4-hexadiene, and 1,4-bis(4-pyridy1)-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 ID Ag-Schiff base chains and alpha-Keggin polyoxoanion units through the cooperativity of multiform supramolecular interactions, such as intermolecular Ag center dot center dot center dot O weak interactions, Ag center dot center dot center dot pi interactions, pi center dot center dot center dot pi interactions, and hydrogen bonds. The photoluminescent properties of 1-6 have been investigated in the solid state.