Preparation, crystal structures and magnetic properties of three thiocyanato-bridged copper(II) complexes with 2,2′-biimidazole or 2-(2′-pyridyl)imidazole as terminal ligands

Abstract

The synthesis, crystal structures and variable temperature magnetic investigation of three new thiocyanato-bridged copper(II) complexes with 2,2′-biimidazole (H 2bim) or 2-(2′-pyridyl)imidazole) (pyim) as coligands, {[Cu(H 2bim) 2][Cu(H 2bim)(NCS) 2(SCN) 0.6667(NO 3) 0.3333] 2} · 2H 2O ( 1), [Cu(H 2bim)(NCS) 2] n ( 2) and [Cu(pyim)(NCS) 2] n ( 3) are reported. Complex 1 contains centrosymmetric trinuclear species where central [Cu(2)(H 2biim) 2] 2+ cations and peripheral [Cu(1)(H 2biim)(NCS) 2(SCN)] − anions are linked through single end-to-end thiocyanato bridges. Complexes 2 and 3 are made up of neutral zigzag chains of copper(II) ions linked by single ( 2) and double ( 3) end-to-end thiocyanato bridges. A bidentate H 2bim ligand ( 2) or pyim ( 3) and a terminal N-thiocyanate group ( 2) complete the coordination spheres around each copper atom. The values of the intramolecular ( 1) and intrachain ( 2 and 3) copper–copper separations are 5.6143(5) ( 1), 5.6744(3) ( 2) and 6.0797(11) Å ( 3). Magnetic susceptibility measurements for 1– 3 in the temperature range 1.9–295 K show the occurrence of weak intramolecular ( 1) and intrachain ( 2 and 3) antiferromagnetic interactions [ J = −0.10 ( 1), −0.24 ( 2) and −0.03 cm −1 ( 3), the Hamiltonians used being H ˆ = - J ( S ˆ 1 · S ˆ 2 + S ˆ 2 · S ˆ 3 ) ( 1) and H = − J∑ i ( S ˆ i · S ˆ i + 1 ) ( 2 and 3)]. The magnitude and nature of these magnetic interactions are discussed in the light of the respective structures and they are compared with those reported for related systems.