A trinuclear nickel(II) cluster containing a ditopic redox active ligand: Structural and magnetic properties

Abstract The preparation of a trinuclear Ni2+ ionic complex containing the bridging ligand 2,6-bis-(8-quinolylamino)-4-(tert-butyl)phenol (H3LtBu) as a phenolate monoanion and perchlorate counteranions is described. The structure contains a rare nearly planar disc-like Ni3O3 core with large Ni-O-Ni angles, with each equivalent of the ligand bridging two Ni2+ ions binding facially to each ion. Variable temperature magnetic susceptibility data from 1 indicate moderate intramolecular antiferromagnetic interactions between the three S = 1 Ni2+ ions (JNi-Ni = -20.7 cm-1) and a diamagnetic (S = 0) ground state. Broken symmetry density functional theory calculations (DFT) at the UB3LYP/def2-TZVP level support the experimental results. The structure and properties of 1 stand in contrast to the other reported complex of H3LtBu, Cu4(LtBu)4, which features the ligand in an unusual dianion-aminyl radical oxidation state. Oxidation of 1 produced a black intractable material that could not be adequately characterized.