On the dependence of spectra of NIR polymethine dyes on the central chromophore ring

The trends in spectral data of two series of dyes containing either two ben zothiazole or four dimethylaminophenyl side chromophores connected by a 7-m embered aliphatic: chain in the central chromophore implemented by cyclohex ene, furanone or cyclopentene ring are compared. In both series, the effect of the central chromophore ring variation on the maximum wavelength lambda (max) is studied using the statistical treatment of the chromophores data obtained by quantum-chemical calculations. The significance of the factors influencing lambda (max) is arranged in the order: the chromophore planarit y; mutual angles of individual chromophore planes; the similarity of indivi dual chromophores in the dye; substituents on individual chromophores.