Khodabakhsh Niknam

The polymethine cyanine dyes are a class of organic compounds which chromophores containing π- electrons. The general structure of these dyes is shown in the figure, in which two quaternized nitrogen atoms are linked by a polymethine chain. Both nitrogen atoms are each independently a part of a heteroaromatic moiety, such as pyrrol, imidazole, thiazole, pyridine, quinoline, indole, benzothiazole, etc. Cyanine dye is usually called monomethine, trimethine, pentamethine and heptamethine cyanine for n = 0, 1, 2, 3, respectively.The first cyanine dye was discovered in 1856 by Williams. Later in 1873, Vogel began to use cyanine dyes in photography. Now days they are used as strong spectral sensitizers of photographic emulsions, data saving in optical format (in manufacture of CDs) and biological fluorescent probes. The present study, used Adams procedure to synthesis new pentamethine derivatives containing heterocyclic substitutions such as 3,5- Dimethyl pyridine and 4-Benzyl pyridine in γ position of methine chain. The structure of these novel compounds were investigated by elemental analysis, UV-Vis, IR, Mass and 1 H NMR, 13C NMR spectroscopies.