Intermolecular Interaction and Magnetic Coupling Mechanism of a Mononuclear Nickel(II) Complex

The mononuclear complex [Ni(HOphen)(OSO 3 )(H 2 O) 3 ] · 5H 2 O (HOphen = 1, 10‐phenanthrolin‐2‐ol) was prepared and its single structure was determined by X‐ray crystallography. In this complex, the Ni II ion has a distorted octahedral arrangement. Crystal structure analysis shows that two kinds of π–π stacking interactions and C–H ··· O short contact intermolecular interactions exist among the adjacent complexes. Fitting to the variable‐temperature magnetic susceptibility data gave the magnetic coupling constant, 2 J = –0.98 cm –1 . Theoretical calculations, based on density functional theory (DFT) coupling with the broken‐symmetry approach (BS), revealed that the π–π stacking magnetic coupling pathways resulted in weak ferromagnetic interactions with 2 J = 4.86 cm –1 and 2 J = 4.16 cm –1 , respectively, for the adjacent Ni II ions with separations of 8.568(19) Å and 8.749(32) Å, respectively; whereas the magnetic coupling pathway of the C–H ··· O short contact intermolecular interaction led to a weak antiferromagnetic interaction with 2 J = –17.62 cm –1 for the adjacent Ni II ions with a separation of 10.291(26) Å. The ferromagnetic coupling sign can be explained by the McConnell I spin‐polarization mechanism.