Condensation of 1,1-bis(4-dimethylaminophenyl)ethylene with substituted hyd
roxyketones in acetic anhydride in the presence of perchloric acid yielded
NIR polymethine dyes. The VIS-NIR spectra of the dyes were measured and int
erpreted by the semi-empirical AM1 method of quantum chemistry. The influen
ce of the molecular structure variations and electron density distribution
on the position of the peaks with the largest wavelengths has been studied.
The results indicate that increase of the polyene rigidity and planarity m
ight lead to the increase of maximum absorption wavelength. (C) 1999 Elsevi
er Science Ltd. All rights reserved.