Ferromagnetic coupling by the spin-polarization mechanism in a trinuclear VIV triplesalen complex

The first trinuclear vanadium complex [ ( talen t - Bu 2 ) ( V IV O ) 3 ] (1) of a triple tetradentate triplesalen ligand has been synthesized and characterized. The triplesalen ligand ( talen t - Bu 2 ) 6 - provides three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone. In the electronic absorption spectrum of 1 all four ligand field transitions are detected below 21 400 cm−1. The region above 23 000 cm−1 is dominated by strong absorption from imine π → π∗ and ligand-to-ligand CT transitions. The latter may also be described by a combined phenolate-to-vanadium LMCT and vanadium-to-imine MLCT through the empty metal d orbitals in a push–pull type interaction. The temperature-dependent magnetic susceptibility measurements reveal a ferromagnetic coupling of the three VIVO units in the triplesalen complex with J = +0.44 cm−1. The correlation of the electronic structure to the weakness of the ferromagnetic coupling by the spin-polarization mechanism in the trinuclear VO system is discussed.