UV spectral changes from rotational and inversion processes at the nitrogen center in aniline molecules

The decoupling of electrons by nuclear distortion and its influence on the UV spectrum are studied using CNDO/S calculations on aniline type molecules. Spectral changes with respect to the rotational angle of the amine group and the degree of hybridization at the nitrogen atom are investigated. The experimental spectrum is discussed on the basis of calculations performed for a variety of nuclear conformations. In particular, changes of the second (charge transfer) band are considered. INDO calculations of potential curves of aniline for the two degrees of freedom yield barriers of 1.2 kcal/ mole for the nitrogen inversion and of 7.5 kcal/mole for the internal amine rotation at the hybridization angle = 39.35°.