Synthesis and magnetostructural characterization of two ferromagnetic nickel(II) dimers

Abstract

Two new ferromagnetic, end-on azide-bridged nickel(II)-dimers [{Ni(terpy)(N₃)₂}₂]·H₂O 1 and [Ni₂(terpy)₂(N₃)₃(H₂O)]ClO₄·H₂O 2 (terpy = 2,2′∶6′,2″-terpyridine) have been synthesized and magnetostructurally characterized through X-Ray single crystal analysis, IR spectroscopy and magnetic susceptibility measurements. The values of the Ni–N–Ni bridge angle and the magnetic coupling constant, J, are 101.6° and 22.8 cm^–1, respectively, for 1 and 102.5° and 13.6 cm^–1, respectively, for 2. The influence of the Ni–N–Ni bridge angle on the magnetic performance of end-on azide-bridged nickel(II) dimers has been studied by means of extended Hückel molecular orbital calculations. The results indicate that the antiferromagnetic contribution of the global coupling constant decreases for increasing bridge angle between 83 and 115°.