Solvent-dependent formation of two Pb(II) coordination polymers based on 4,4′-azodibenzoic acid linker: crystal structures, fluorescence, and thermal properties

Abstract

Solvothermal reactions of Pb(OAc)2·2H2O with 4,4′-azodibenzoic acid (H2L) in DMSO (DMSO = dimethyl sulfoxide) and DMF/H2O (DMF = N,N′-dimethylformamide) at 90 °C gave two Pb(II) coordination polymers (CPs), [PbL(DMSO)]n (1) and [PbL(H2O)]n (2). Complexes 1 and 2 were characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction. Compound 1 possesses a 2-D staircase-like network based on pairs of left and right helical 1-D [Pb(CO2)2(DMSO)]n chains, and is further assembled into a 3-D supramolecular architecture with a 41263 topology through intermolecular hydrogen bond interactions between the neighboring networks. Within the 1-D Pb–O–Pb chain, the DMSO terminally coordinates to Pb(II). Complex 2 has a 3-D motif containing 2-D Pb-carboxylate layers with H2O bridging neighboring Pb ions in a 4664 topological structure. The formation of 1 and 2 provides insight into the effect of solvents on the construction of CPs under solvothermal conditions. Stabilities and photoluminescent properties of 1 and 2 were also investigated.