Intermolecular interaction and magnetic coupling mechanism between adjacent mononuclear NiII complexes.

A new mononuclear complex, [Ni(dpphen)(NCS)2] [dpphen = 2,9-di(1H-pyrazol-1-yl)-1,10-phenanthroline], has been prepared and its crystal structure is determined by X-ray crystallography. In the NiII complex, NiII is a distorted octahedral geometry. The crystal structure analysis shows that there exist π−stacking interactions and an intermolecular interaction among adjacent complexes. The fitting to the variable-temperature magnetic susceptibility data gave the magnetic coupling constant J = −1.37 cm−1 (Ĥ = -JŜ1 ⋅ Ŝ2). Theoretical calculations reveal that the π-stacking magnetic coupling pathway resulted in an antiferromagnetic interaction with 2 J = −0.22 cm−1 (Ĥ = -2JŜ1 ⋅ Ŝ2), whereas the magnetic coupling pathway of the intermolecular interaction led to a ferromagnetic interaction with 2 J = 0.10 cm−1 (Ĥ = -JŜ1 ⋅ Ŝ2). The calculations also display that there occur both spin delocalization and spin polarization in the π-stacking magnetic coupling system and the magnetic coupling system of the intermolecular interaction. [ABSTRACT FROM AUTHOR]