ELECTRON-DONOR ABILITY OF THE ANNELATED END-GROUPS OF POLYMETHINE DYES

The influence of benzannelation on the electron donor ability of polymethine dye end-groups is studied in terms of the recently proposed quasi-long dye approximation combined with a graphical-theoretical approach. The Sachs-Coulson graph theorem enables the electron donor ability to be expressed in an analytical form and related to the number of annelating rings and to the type of annelation. Both alternant and non-alternant hydrocarbon end-groups are considered, including anti-Hückel ones, as well as nuclei containing heteroatoms. In each case the dependence of the electron donor ability on the number of annelating benzene rings is determined for all possible types of annelation. The results predicted by means of the theory are shown to be in agreement with the literature and experimental data. © 1990.