Intermolecular interaction and magnetic coupling mechanism on a mononuclear Co^II complex

Abstract

Anti-ferromagnetic interaction was observed in a new crystal that consists of mononuclear Co II complexes, namely [Co(PMP)(N 3 )] (PMP ¼ 2,9-bis(pyridin-2-methoxyl)-1,10-phenanthroline); in the mononuclear complex Co II has a distorted trigonal-bipyramidal geometry. Analysis for the crystal structure indicates six magnetic coupling pathways among adjacent complexes, in which three involve -stacking and the other three deal with intermolecular interactions. The fitting for the variable-temperature magnetic susceptibilities with the Curie-Weiss formula shows an anti-ferromagnetic interaction between adjacent Co II ions with ¼ À5.49 K ¼ À3.82 cm À1 . Theoretical calculations on the spin section reveal that the three -stacking systems result in magnetic coupling constants 2J ¼ À0.10 cm À1 , À0.10 cm À1 , and 1.24 cm À1 , respectively, and the three intermolecular interactions lead to weak anti-ferromagnetic interactions with 2J ¼ À0.36 cm À1 , À0.26 cm À1 , and À0.32 cm À1 , respectively. The theoretical calculations and the experimental magnetic data imply that the anti-ferromagnetic interaction involves the orbital contribution of the relevant Co II ions.