Correlating Magnetic Exchange in Dinuclear Bis(phenolate)-Bridged Complexes: A Computational Perspective

Abstract

Abstract Density functional theory (DFT) calculations were performed to analyse the magnetic properties of dinuclear Ni–Ni and Cu–Cu bis(phenolate)-bridged complexes with two antiferromagnetically-coupled metals. The estimated coupling constants J are −384.8 and −375.3 cm−1 for the two Cu complexes and −85.7 cm−1 for the Ni complex, which are consistent with the experimental values. Analysis of overlap integral can explain the difference in the coupling J between Ni and Cu complexes: Two dx2 − y2 orbitals of the copper complexes are located on the same plane as that of a phenolate ligand, and therefore produce the strong J coupling, whereas those of the nickel complex are tilted from the plane of phenolate ligand because of asymmetric environment around Ni atom, and produce moderate J coupling. We also examined the dependences of magnetic interaction in terms of several important geometrical parameters. The M–O–M bond angle is the key parameter for antiferro–ferromagnetic transition, which is consistent with previous studies for the other complexes. Also, increasing the M–O–O–M dihedral angle, decreasing the M–O–M bond angle and large hinge distortions on these complexes effectively enhance the ferromagnetic exchange, which is a desired condition for a better molecular magnet.