Syntheses, structures, and magnetic properties of cobalt(II) and nickel(II) coordination polymers based on a V-shaped ligand

Abstract

Two coordination polymers [Co2(TA)(4,4′-bipy)2(H2O)2]·H2O (1) and [Ni2(TA)(4,4′-bipy)2(H2O)4]·3H2O (2) were prepared by hydrothermal reactions of MCl2·6H2O (M = Co, Ni) with a V-shaped ligand TDPA (3,3′,4,4′-thiodiphthalic anhydride) and a I-shaped N-donor co-ligand (4,4′-bipy). They were characterized by elemental analyses, thermogravinetric analyses, and magnetic behavior. As is expected, TDPA hydrolyzes into the corresponding tetra-carboxylate acid H4TA (3,3′,4,4′-thiodiphthalic acid) during the reactions. Co2 dimer and Ni mononuclear center are connected into two-dimensional (2D) layers by H4TA and 4,4′-bipy bridge in 1 and 2, respectively. The most amazing feature is that 1 and 2 exhibit interesting spin-canting metamagnetism and weak ferromagnetic behavior, respectively, with the critical Néel temperature of TN =4K for 1 and TN =13K for 2, based on variable temperature magnetic susceptibility measurements. In low mono- or dinuclear metal system, such magnetic behaviors have rare been observed. Furthermore, complex 1 will be a potential metamagnet material.