Synthesis, crystal structures and magnetic properties of a phenoxo-bridged dinuclear Cu^II complex and a dicyanamide bridged novel molecular rectangle based on it

Abstract

The phenoxo-bridged dinuclear Cu^II complex [Cu₂L₂(NCNCN) ₂] (1) and the dicyanamide-bridged molecular rectangle [Cu₄L₄{μ^1,5-(NCNCN) ₂}]•(ClO₄)₂ (H₂O)₂ (2) were synthesized using the tridentate reduced Schiff-base ligand HL {2-[(2-dimethylamino-ethylamino)methyl]phenol}. The complexes were characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 2 was formed through the joining of the phenoxo-bridged dinuclear Cu₂O₂ cores of 1 via the μ_1,5-bridging mode of dicyanamide. The structural properties of the Cu₂O₂ cores in two complexes are significantly different. The geometry of the copper ions is distorted trigonal bipyramid in 1 but is nearly square-pyramidal in 2. These differences have a marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J = –185.2 and –500.9 cm^–1 for 1 and 2, respectively) differ considerably.