Crystal structures and magnetic properties of triple helical binuclear complexes with bis(bidentate) diazine ligands

Abstract

Three triple helical binuclear complexes [Ni 2(L 1) 3] · (ClO 4) 4 · (H 2O) 3 ( 1) (L 1 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), [Ni 2(L 2) 3] · (ClO 4) 4 · (H 2O) 3 ( 2) (L 2 = 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene) and [Mn 2(L 1) 3] · (ClO 4) 4 · (H 2O) 3 ( 3) have been studied, where the L i ligand possesses a rotationally flexible single N–N bond. In complexes 1– 3, the three bis(bidentate) diazine ligands wrap around two metal cations with a spiral conformation, leading to a triple helicate with C 3 symmetry. Magnetic investigations revealed that antiferromagnetic interactions are operative between the two metal ions linked by the triple diazine bridges, with J = −2.97 and −5.40 cm −1 for 1 and 2, respectively. Variable temperature magnetic data for 3 indicates a weak ferromagnetic interaction between the two manganese(II) centers with J = 1.24 cm −1. The X-ray powder diffraction of 3 is also discussed.