Synthesis and Spectroscopic Characterisation of Some Novel Butadienyl Asycyanine Colorants having Lepidine Moiety

Twenty-one novel chromophoric chain β-substituted butadienyl asycyanine colorants have been synthesized by catalytic condensation of (i) dimethylaminostyryl phenyl ketone, (ii) 4ʹ-dimethylaminostyryl-4ʹ-nitrophenyl ketone and (iii) 4ʹ-dimethylaminostyryl-4ʹ-methoxyphenyl ketone with seven lepidinium methyliodide salts in ethanolic DMF medium using piperidine as basic catalyst. These colorants were synthesized with the objective to study the effect of electron acceptor and electron donor group substituent at 4ʹ-position in the chain β-phenyl nucleus on visible absorption maxima. The newly prepared colorants were found to exhibit uniform increase in absorption maxima i.e. Red shift (RS), when collated with analogues having no substituent in the β-phenyl nucleus. Again the absorption maxima of the title colorants were found to be higher than the absorption maxima of previously prepared butadienyl colorants having quinoline mioety of same conjugated system.