Structure and properties of new classes of coupled polymethine dyes

The structure and the energy spectra of new classes of coupled polymethines (CP) (coupled cyanines, merocyanines and oxonoles) were investigated theor etically. The CPs may be considered as being composed of two identical or t wo different streptopolymethine fragments or as derivatives of poly(peri-na phthylene)s. All CPs display low-energy S-1(o) -->(1) S-1 transitions with a high transition probability. The transition energies are comparable with those of the streptopolymethine substructures. The similarity of the energy spectra of streptopolymethines and CPs is determined by the symmetry of th e frontier MOs of the streptopolymethine fragments and the CPs. (C) 1999 El sevier Science Ltd. All rights reserved.