VANADYL METAL MESOGEN DERIVATIVES - AN EPR STUDY

An EPR study of the metallo-organic compounds bis(N-pentyl, 4-(4-decyloxybenzoyloxy) salicylaldiminato) of oxovanadium (IV) and bis(N-(4-pentyloxyphenyl), 4-(4-decyloxybenzoyloxy) salicylaldiminato) of oxovanadium (IV) is presented. Both materials are mesogenic and undergo some phase transitions between room temperature and 150 degrees C (for the first compound) and 270 degrees C (for the second one). The EPR signals are due to the vanadyl group. The spectra have been measured at different temperatures and the changes in them have been correlated with some of the phase transitions. Modifications in the spectra occurring after several heating-cooling cycles dependent on the presence or absence of an applied magnetic field (up to 1.4 mT) are also observed. The behaviour is discussed in terms of molecular orientations in the presence of a magnetic field. A qualitative discussion of the different contributions to the magnetic susceptibility is given.