LOCALIZATION OF PI-ELECTRONIC EXCITATION - UV-VIS SPECTRA OF SOME SUBSTITUTED AZOBENZENES, STILBENES AND BENZYLIDENE-ANILINES

A band analysis of UV spectra based on a normal logarithmic distributi on function is presented. The pi-electronic transitions are interprete d in terms of the localization on molecular fragments and charge trans fer between them. The localization is characterized by Luzanov's fragm ental participation numbers L(A) obtained by a transition density matr ix formalism within a standard PPP calculation. The charge transfer nu mbers 1(AB) describe the interaction between different fragments. In a ll transitions some molecular fragments are predominantly involved in consequence of asymmetry of the substituted systems. Examples of a det ailed charge transfer and localization analysis are, given and reflect the various aspects of prior fragmentation schemes.