Spectral and non-linear optical properties of cyanine bases' derivatives of benzo[c,d]indole

The complex investigation of the cyanine bases, containing benzo[c,d]indole as residue group was carried out by linear and non-linear optical spectroscopic and quantum-chemical modelling methods. It was found that non-linear optical properties were more sensitive to the nature of the varied donor terminal group than the absorption spectra; the increase of the donor strength in indolenine, benzothiazole, quinoline, and pyridine causes an increase of the second and third hyperpolarizibilities by a factor of 3.5, which is qualitatively in good agreement with the experimental data.