Internal Rotation of N- (p-methoxy-benzylidene) -p-n-butylaniline (MBBA) and Benzylidene-aniline (BA)

The UV absorption spectrum of gaseous MBBA was observed at 110°C. The electronic structures of BA and MBBA were calculated as a function of the twist angle of aniline ring out of the C=N-C plane by means of the CNDO/S + CI method. The twist angle in MBBA was estimated as 52.0° in nematic, 66.3° in metastable solid, and either 44.4° or 82.7° in stable solid using the calculated and observed electronic spectra and the observed Raman scattering frequency. A potential energy curve for the internal rotation in MBBA in solid states was proposed to give a reasonable interpretation of the experimental data and the calculated results.