TRANSITION-METALS COMPLEXED TO ORDERED MESOPHASES - SYNTHESIS, MESOMORPHISM, AND X-RAY AND EPR CHARACTERIZATION OF A HOMOLOGOUS SERIES OF N-(4-DODECYLOXYSALICYLIDENE)-4'-ALKYLANILINES COMPLEXED TO OXOVANADIUM (IV)

A number of mesogenic bis[4-(dodecyloxy)-N-(4'-R(n)-phenyl)salicylideneiminato]oxovanadium(IV) complexes (1-7, R(n) = CH3, C2H5, C3H7, C4H9, C6H13, OC6H13, C8H17, respectively) have been synthesized and characterized by polarizing microscope observations, DSC measurements, X-ray diffraction, and EPR spectroscopy. These compounds are thermally stable and to not decompose on melting. Complexes 1-5 show two different solid phases K1 and K2. In addition, 4 and 5 exhibit a liquid-crystalline smectic A phase (monotropic in 4 and enantiotropic in 5). On the other hand, 6 and 7 along with a single solid phase, display a smectic C (enantiotropic in 6 and monotropic in 7) and an enantiotropic smectic A phase. Variable-temperature EPR spectra are accounted for on the basis of paramagnetic metal ions experiencing different magnetic environments. For each mesophase, matching X-ray, and EPR data, the molecular packing mode is suggested. Comparing 1-7 with the homologous copper complexes, the contribution of the metallic center to the mesomorphic properties is discussed.