Synthesis and antimicrobial activity of certain novel monomethine cyanine dyes

A series of novel monomethine cyanine dyes were synthesized by using 3-methyl-5-substituted-1-phenyl-pyrano[2,3-c]pyrazole derivatives 2a-c. Reaction of equimolar ratios of 2a-c with 2(4)-methyl heterocyclic quaternary salts afforded the corresponding monomethine cyanines 3a-c. Reaction of compound 5 with 2(4)-methyl heterocyclic quaternary salts gives monomethine 6a-c. Condensation reaction of equimolar ratios of compounds 7 and 9a,b with 2(4)-methyl heterocyclic quaternary salts afforded the corresponding monomethine cyanines 8a-c and 10a,6 respectively. The new synthesized monomethine cyanine dyes were identified by elemental analyses, IR,H-1-NMR and Ms spectral data. The electronic absorption spectra in ethanolic solution of novel monomethine cyanine dyes were measured and the antimicrobial activity of some selected monomethine cyanine dyes was discussed. (C) 2003 Elsevier Ltd. All rights reserved.