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

The first trinuclear vanadium complex [(talent-Bu2)(VIVO)3][(talent-Bu2)(VIVO)3] (1) of a triple tetradentate triplesalen ligand has been synthesized and characterized. The triplesalen ligand (talent-Bu2)6-(talent-Bu2)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.

We have synthesized the first trinuclear VIV = O triplesalen complex. The three spin centers are ferromagnetically coupled as it was intended by the meta-phenylene bridging motive due to spin-polarization. The electronic structure obtained from absorption spectroscopy is correlated to the weakness of the ferromagnetic interactions providing new instructions for an improved ligand design.Figure optionsDownload as PowerPoint slide