Crystal structures and magnetic behaviour of three new azido-bridged dinuclear cobalt(II) and copper(II) complexes

Three dinuclear cobalt(II) and copper(II) complexes with double end-on (EO) azido bridges, [Co₂(DMP)₂(N₃)₄] (1), [Cu₂(DMP)₂(N₃)₄] (2) and [Cu₂(PAP)₂(N₃)₄] (3) (DMP = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine; PAP = 1-phenyl-2-(2-pyridyl)-1- azapropylene) have been synthesized and characterized by single-crystal X-ray diffraction and magnetic analyses. The EPR spectra of powder samples for the two copper(II) complexes have also been examined at room temperature and 77 K, respectively. In the isomorphous complexes 1 and 2, the metal ions are penta-coordinated with distorted trigonal bipyramidal geometries, and the EO azido bridges assume an equatorial-axial disposition between metal ions. In contrast, the copper(II) ion in complex 3 adopts a distorted square pyramidal geometry, and the EO azido bridges assume a basal-apical disposition between metal ions. According to magnetic studies, the double end-on azido bridges mediate ferromagnetic coupling with J = 18.1 cm^-1 in 1, antiferromagnetic coupling with J = -27.6 cm^-1 in 2, and ferromagnetic coupling with J = 35.0 cm^-1 in 3.