Synthesis and spectra of tetrakis (4-dimethylaminophenyl) hexadienes

Condensation of 1,1-bis(4-dimethylaminophenyl)ethylene with substituted hydroxyketones in acetic anhydride in the presence of perchloric acid yielded NIR polymethine dyes. The VIS¯NIR spectra of the dyes were measured and interpreted by the semi-empirical AM1 method of quantum chemistry. The influence 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 might lead to the increase of maximum absorption wavelength.