A three-dimensional coordination polymer based on linear trinuclear copper(ii) clusters featuring a ferromagnetic exchange interaction

Abstract

A new triazine-based dicarboxylic acid, 2,4-bis(4-aminobenzoic acid)-6-(dimethylamino)-1,3,5-triazine (H₂L), has been designed and prepared, which has been used for the support of a new coordination polymer constructed from trinuclear copper(II) clusters. The compound was structurally authenticated by single-crystal X-ray diffraction revealing that the compound possesses a three-dimensional (4,8)-connected alb network constructed from trinuclear copper(II) clusters with the general formula [Cu₃(L)₂(μ₂-OH)₂] (1). Additionally, compound 1 contains left- and right-handed helical chains along the b axis, which are interlinked by the trinuclear copper(II) clusters. In the basic trinuclear copper(II) cluster, the central copper ion is located on an inversion center with strictly planar four-coordinate coordination geometry, while the coordination spheres of the terminal copper ions are square pyramidal. The three copper atoms are in an exactly linear arrangement, and adjacent coppers are connected by a hydroxo bridge and a bidentate syn–syn carboxylate group. Variable-temperature magnetic susceptibility measurements reveal a ferromagnetic coupling between adjacent copper(II) ions with J = 42.39 cm⁻¹, which is confirmed by the EPR spectrum.