Photodynamics of polyene-polymethine transformations and spectral fluorescent properties of merocyanine dyes

Absorption and fluorescence spectrum band moments are determined in a wide range of solvents with different polarities for inverse solvatochromic di-, tetra-, and hexamethinemerocyanines derived from 1,3-diphenyl-2,3-dihydro-1H-benzimidazole. The close vicinity of the excited state to the cyanine limit has caused a significant increase in fluorescence quantum yields and a decrease in Stokes shift seen for higher merocyanine vinylogues.