Four new metal–organic coordination polymers with non-coordinating biphenyl groups: Synthesis, characterization, magnetic and luminescent properties

Four new coordination polymers, namely [Mn(L)2(H2O)2]∞ (1), [Co(L)2(H2O)2]∞ (2), [Zn(L)2(H2O)2]∞ (3) and [Cd(L)2(H2O)2]∞ (4) (L = biphenyl-4-carboxylate), were synthesized and structurally characterized by elemental analyses, IR spectra, X-ray powder diffraction and single crystal X-ray diffraction analysis. Structural analyses show that 1–4 all assume isostructural two-dimensional (2D) 44 networks. The results indicate that non-coordinating biphenyl groups of ligands play an important role in governing the formation of the final frameworks. There exist antiferromagnetic coupling interactions between the MII ions in 1 as well as in 2. Moreover, intense luminescent emissions of 3 and 4 were attributed to the ligand-to-ligand charge transfer (LLCT).