Syntheses, structures and luminescent properties of seven metal–organic frameworks constructed with a rigid bis(imidazole) ligand and versatile carboxylate acids

Abstract

Seven new metal–organic frameworks, namely, [Zn₅(μ₃-OH)₂(bdc)₂(bimf)₂]·4H₂O (1), [Zn(bdc)(bimf)]·2H₂O (2), [Cd(bdc)(bimf)(H₂O)]·2H₂O (3), [Cd₄(cdc)₄(bimf)₂(H₂O)₂]·2H₂O (4), [Cd(cdc)(bimf)] (5), [Zn₂(Hbtc)₂(bimf)₂]·H₂O (6) and [Cd₃(btc)₂(bimf)₃(H₂O)]·2H₂O (7) have been synthesized and structurally characterized (H₂bdc = 1,4-benzenedicarboxylic acid, H₂cdc = 1,4-cyclohexanedicarboxylic acid, H₃btc = 1,3,5-benzenetricarboxylic acid and bimf = 9,9-dimethyl-2,7-bisimidazolylfluorene). Compound 1 displays a uninodal 12-connected fcu-framework based on pentanuclear zinc clusters. Compound 2 exhibits a 4-fold interpenetrating framework of SrAl₂-topology. Compound 3 presents a 2-fold interpenetration of (4,4) net. Compound 4 shows a uninodal 8-connected framework of hex-topology. Compound 5 features a binodal framework of PtS-topology. Complex 6 features a binodal framework with an unusual (6⁶)·(6⁴·8²) topology. Complex 7 defines a pentanodal framework containing 3, 4 and 8-connecting nodes. Their photochemical properties were measured.