Energy structures and electronic-transition wavelengths for trinuclear polymethine dyes

A study has been made on the energy structures and long-wave electronic transitions for linear trinuclear polymethine dyes by the method of additive generating functions. The necessary and sufficient conditions have been established for the occurrence of local levels related to the central nucleus. It is found that the bisvinylene shift is dependent on the structure of the central nucleus in this class of dyes. The relationship fits the available measurements, and it is predicted that there is a positive bridge effect, namely an increase in the bisvinylene shift in trinuclear dyes by comparison with binuclear ones.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 10–21, January–February, 1987.