Syntheses, structures, photoluminescence and magnetic properties of four new metal–organic frameworks based on imidazoleligands and aromatic polycarboxylate acids

Abstract

Four metal–organic coordination polymers, {[Cu₂(4,4′-bibp)₂(NO₂)₃)]·(NO₂)(H₂O)}_n (1), [Cd(bdc)(4,4′-bibp)]_n (2), {[Co₂(bdc)₂(4,4′-bibp)₃(H₂O)₂]·(H₂O)₂}_n (3), [Zn(Hbtc)(1,4-bix)]_n (4) (4,4′-bibp = 4,4′-bis(1-imidazolyl)biphenyl; 1,4-bix = 1,4-bis((1H-imidazol-1-yl)methyl)benzene; H₂bdc = 1,4-benzenedicarboxylate; H₃btc = 1,3,5-benzenetricarboxylate) were obtained under hydrothermal conditions and characterized structurally. X-Ray diffraction analysis reveals that the four complexes exhibit new frameworks due to diverse coordination conformations. In copper compound 1, with mixed-valence copper(II)–copper(I), rigid linear 4,4′-bibp ligands connect two adjacent layers and the whole structure is a three-dimensional 6,6-connected network. In cadmium compound 2, 4,4′-bibp and bdc anions as bidentate ligands coordinate to cadmium cations to form a three-dimensional 4,4-connected network with a 3-fold interpenetrating framework. In cobalt compound 3, 4,4′-bibp and bdc anions also act as bidentate ligands, and coordinate to cobalt cations to form a three-dimensional 4,6-connected network. Zinc compound 4 shows that both the 1,4-bix ligand and btc anions act as bidentate bridging ligands, and connect the zinc cations to give a 2D polycatenated array structure. The magnetic properties for copper compound 1 and luminescent properties for cadmium compound 2 and zinc compound 4 are also discussed in detail.