Synthesis, visible absorption, photosensitisation and antimicrobial activity of some butadienochromophoric chain-substituted asymmetric cyanines

Abstract

Some butadienochromophoric chain-substituted asymmetric cyanines (BCCSAC) have been synthesised by the catalytic condensation of three chalcones, viz. 4-dimethylaminostyryl phenyl ketone, 4-dimethylaminostyryl 4'-nitrophenyl ketone and 4-dimethylaminostyryl 4'-hydroxyphenyl ketone, separately, with 6-substituted quinaldinium ethiodides. These BCCSAC were prepared with the object of studying the effects of electron donor and acceptor substituents at the 4'-position in the chain β-phenyl nucleus, of elongation of the chromophoric chain on the visible absorption maxima and spectral photosensitivity, and of investigating their antimicrobial efficacy. The dyes were found to absorb at longer wavelengths and to show uniform bathochromic shifts compared with analogues having no substituents in the chain and in the β-phenyl nucleus. These BCCSAC are concluded to be superior sensitisers than the corresponding arylidenologues, in accord with the authors' previous observations. Purified samples were also subjected to in vitro antimicrobial screening to evaluate their bactericidal activity on the basis of inhibitory zone data, collected at different concentrations, and many of them were found to exhibit antistaphylococcal and antiescherichial activities.