Magnetic behaviour of bis(5,7-dichloro-8-hydroxyquinolinato)oxovanadium(IV)

The magnetic susceptibility of the title compound was measured between 1.9 and 300 K. It shows a Curie–Weiss behaviour in the temperature range between 50 and 300 K. Below 40 K, a ferromagnetic interaction between the VO2+ groups is observed, which was also confirmed by an investigation of the magnetization as a function of the magnetic field, at 5 K. The mechanism of the interactions was analyzed theoretically using a high temperature series expansion. An excellent agreement between experimental and theoretical data was obtained with the exchange integral J=2.73 cm−1. The presented results constitute the first direct evidence of the formation of ··VO···VO···VO·· ferromagnetic chains in certain oxovanadium(IV) complexes.