A trinuclear nickel(II) Schiff base complex with phenoxido- and acetato-bridges: combined experimental and theoretical magneto-structural correlation

We describe the synthesis and characterization of a new trinuclear Ni(s) Schiff base complex of formula [Ni-3(L)(2)(NCS)(2)(OAc)(2)(CH3OH)(2)] (1) where HL is the 1:1 condensation product of 2-picolylamine and o-vanillin. The crystal structure of complex 1 shows that the two terminal Ni(II) ions are connected to the central one through a phenoxido- and a syn-syn acetato bridge, giving rise to a very bent configuration in the Ni-3-core. Magnetic susceptibility measurements show the presence of a weak antiferromagnetic coupling with J = -3.22(2) cm(-1). We also report a magneto-structural correlation, performed with all the magnetically characterized Ni(II) trimers with similar bridges, showing a linear dependence between the J value and the dihedral angle (theta) between the planes containing the Ni-O-Ni and the carboxylate bridges. The super-exchange interaction is investigated by extensive density functional calculations within the broken symmetry approximation which show good agreement with the experimental data. The analysis of the spin density distribution and the shape of the magnetically active single occupied molecular orbitals (SOMO) provide a mechanism of exchange coupling through the bridging groups.

Automated summary

A new trinuclear Ni(s) Schiff base complex was synthesized and characterized, showing a bent structure and weak antiferromagnetic coupling. The study revealed a linear correlation between the J value and certain angles, indicating a mechanism of exchange coupling through bridging groups.