Synthesis and absorption spectra of new polymethine cyanine dyes

Abstract

The reaction of a ratio of 1 mol of 2-chloro- 1-formyl crotonic ester 1 with 2 mol of an appropriate 2(4)-heterocyclic quaternary salt afforded the novel pentamehine cyanine dyes 2a– 2c. Condensation reaction of compound 1 with aromatic amines followed by reaction with 2(4)-heterocyclic quaternary salt resulted in aza-tetramethine cyanine dyes 4a– 4e. Condensation of compound 1 with active methylene compounds and acetophenone derivatives, followed by reaction with 2 mol of 2-methylquinoline methyliodide afforded the corresponding heptamethine cyanine dyes 6a– 6f. The structures of the novel compounds were established by elemental analysis, visible/near-infra-red (near-IR) absorption, IR, 1H NMR spectroscopy and mass spectra. Absorption of electromagnetic radiation of some selected new polymethine dyes was studied. The relationship between the constitution and properties of these dyes has been studied.