Semi-rigid imidazolium carboxylate controlled structural topologies in zwitterionic coordination networks

Abstract

The zwitterionic coordination networks [L2Mn(H2O)2]∞ (1), [L2Co(H2O)2]∞ (2), [L2Ni(H2O)4]∞ (3), [L2Cu]∞ (4), [L2Zn(H2O)2]∞ (5) and [L3Cd2(Br)2]∞ (6) were synthesized from the reaction between the semi-rigid imidazolium carboxylate spacer LH2+Br− and the corresponding metal nitrates in DMF/H2O at 130°C. The solid state structures of 1–6 were confirmed by the single-crystal X-ray diffraction technique. The molecules 1, 2 and 5 are isostructural one-dimensional coordination polymers. 3 was isolated as a monomer and the monomers are associated into a three dimensional fashion through O–H⋯O hydrogen bonds, while 4 was isolated as a 1D coordination polymer. Compound 6 was constructed as a two-dimensional coordination framework with a rare [Cd2(μ2-Br)2] core. The purity of 1–6 in the bulk was confirmed by the powder X-ray diffraction technique. Furthermore the electronic properties of 1–6 were studied using UV–Vis spectroscopy and the thermal stabilities of 1–6 were confirmed by TGA.