Synthesis, electronic structure, and absorption spectra of the merocyanines derived from pyranes and benzopyranes

The synthesis, peculiarities of the electron structure and spectral properties of the merocyanine derivatives of the pyranes and benzopyranes with nitrogen-containing heterocycles as donor end groups are presented. It is established that an annelation of the pyrane residue leads to bathochromic shift of the absorption band. Because of the considerable change in the dipole momentum upon excitation, the merocyanines studied show high sensitivity to the solvent polarity.