Structural diversity and magnetic properties of five copper–organic frameworks containing one-, two-, and three-types of organic ligands

Abstract

Five novel compounds {[Cu(CMA)]·0.8H(2)O}(n) (1), {[Cu(CMA)(bpy)(0.5)]·0.5DMF}(n) (2), {[Cu(CMA)(bpy)(H(2)O)]·0.5H(2)O}(n) (3), {[Cu(2)(CMA)(DPA)(bpy)(2)(H(2)O)]ClO(4)}(n) (4) and {[Cu(3)(CMA)(DPA)(bpy)(4)(OH)](ClO(4))(2)·3H(2)O)}(n) (5) (H(2)CMA = 3-(carboxymethoxy)-5-methylbenzoic acid, HDPA = 2-(3,5-dimethylphenoxy)acetic acid, bpy = 4,4'-bipyridine) were synthesized and characterized by single crystal X-ray diffraction. Interestingly, the kinds of ligands included in these compounds are different: 1 contains single-ligand CMA(2-); 2 and 3 comprise two kinds of ligands (CMA(2-) and bpy); 4 and 5 cover three kinds of ligands (CMA(2-), DPA(-) and bpy). Structural analyses reveal that 1-3, and 5 are three-dimensional (3D) frameworks, while 4 is a 2D layer. Noteworthily, 1 possesses two types of channels: six-star and hexagonal ones. 3 displays a three-fold interpenetrating 3D framework. The structural diversity of the compounds may have originated from different anions, solvents and temperatures. Variable-temperature magnetic susceptibility measurements were carried out on compounds 1, 2 and 4, and the magnetic properties are dramatically different due to the structural diversities. The magnetic data of 1 shows an antiferromagnetic interaction with J = -54.84 cm(-1) estimated from the Bonner-Fisher model. The magnetic data of 2 was least-square fitted to the Blenaey-Bowers equation with J = -131.01 cm(-1), indicating the existence of a strong antiferromagnetic interaction between two adjacent Cu(2+). The magnetic data of linear tetranuclear structure 4 was best fitted to the expression derived from the Hamiltonian H = -2(2J(1)S(1)S(2) + J(2)S(1)S(1*)). The best fitting parameters are J(1) = -17.48 cm(-1) and J(2) = -65.26 cm(-1), which also indicate an antiferromagnetic interaction. Simultaneously, the magneto-structural relationship was discussed.