Exploring methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate and varying flexible bis(imidazole)-based synthons as building blocks for the construction of diverse cadmium coordination polymers

Abstract

Three Cd(II)-based coordination polymers (CPs) with unique structures and topologies, namely, [Cd2(L)2(bimb)2(H2O)2]n (1), {[Cd(L)(bmib)0.5(H2O)](CH3OH)0.5}n (2) and [Cd(L)(beib)0.5(H2O)]n (3) (H2L = methyl-3-hydroxy-5-carboxy-2-thiophenecarboxylate, bimb = 1,4-bis(imidazol-1′-yl)butane, bmib = 1,4-bis(2-methylimidazolyl)butane and beib = 1,4-bis(2-ethylimidazolyl)butane) have been successfully constructed and characterized by single crystal X-ray structure determination, IR spectra, elemental analyses and powder X-ray diffractions. X-ray results showed compound 1 features a new 2-nodal 5,6-connected 3D network with a point symbol of {45.5.63.7}2{42.54.69}. Compound 2 exhibits a rare 6-fold interpenetrating dia 3D network. Compound 3 bears a hydrogen bonded-extended 3D supramolecular structure based upon sql layers assembled from dinuclear Cd(II) units. Thermal stability and solid photoluminescence properties of compounds 1–3 were studied. Significantly, compound 1 can sense nitrobenzene through the luminescence quenching effect.