AM1 STUDIES OF PHOTOELECTRON-SPECTRA - 12 - PHOTOELECTRON-SPECTRUM AND STEREOISOMERISM OF 10-VINYLPHENOTHIAZINE

Empirical analysis of the photoelectron spectrum of 10-vinylphenothiaz ine demonstrated that in the gaseous phase, this compound exists as tw o stereoisomers that differ in the electronic structure. One of them c ontains the planar amine fragment. The second stereoisomer is characte rized by the quasi-axial orientation of the substituent. The X-ray dif fraction data for the molecules and donor-acceptor complexes of phenot hiazine derivatives as well as for the radical-cation of 10-ethylpheno thiazine were used for obtaining structure correlations. These correla tions and the results of AM1 calculations indicate that pyramidal inve rsion of the nitrogen atom occurs simultaneously with inversion of the ring. In the stereoisomer containing the planar heterocyclic fragment , the dihedral angle between the planes of the benzene rings is 180 de grees. According to the data of photoelectron spectroscopy, this stere oisomer is characterized by a substantial deviation of the vinyl group from the plane of the heteronucleus. In the stereoisomer with the qua si-axial arrangement of the substituent, the dihedral angle between th e planes of the benzene rings is 150 degrees. Similar values of the an gles were obtained in the AM1 calculations of the potential of interna l motion of 10-vinylphenothiazine.