Synthesis and properties of new polymethine dyes based on bis-dimethylaminophenylethylene moiety

Polymethine dyes have attracted much attention due to their potential functions for high-tech uses as organic colorants. The work herein comprises an investigation of a new class of polymethine dyes 3 and 5 which have been synthesized by the reaction of 4,4'-vinylidene-bis(N,N-dimethylaniline) 1 with two aldehydes such as 4-diphenylaminobenzaldehyde 2 and N-ethylcarbazole-3-carboxaldehyde 4. Both methine dyes based on bis-dimethylaminophenylethylene moiety showed broad absorption spectra with high molar extinction coefficient in the range of 600-700 nm and their maximum absorption spectra were exhibited at 650 and 647 nm, respectively. The absorption spectra of the reversible colored form which converted from leuco form appeared with addition of acid. (c) 2005 Elsevier Ltd. All rights reserved.