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.