Synthesis and spectral properties of merocyanine dyes based on polynitrofluorenes

Abstract

The di-, tetra- and hexamethinemerocyanines derived from di-, tri- and tetranitrofluorene, containing heterocyclic indolylidene residue were synthesized and their absorption spectra in the solvents of different polarity were investigated. A quantum-chemical analysis of the electronic structure of the synthesized merocyanines was performed and the types of electronic transitions in their molecules were calculated using DFT and TDDFT methods with the B3LYP/6-31G(d,p) basis. It was shown that with increasing electronacceptor properies of the fluorene core the electronic structure of the merocyanines can change from a neutral polyene to an ideal polymethine, which significantly affects the position, intensity and shape of the absorption bands, as well as vinylene shifts and deviations.