1,1′-Diethyl-2,2′-carbocyanine iodide

1,1'-Diethyl-2,2'-carbocyanine iodide, also known as Pinacyanol iodide, is a fluorescent cationic cyanine dye. The molecule contains two nitrogen atoms interacting through a conjugated pi system with one nitrogen bearing a formal positive charge, setting up a "push-pull" alkene system that poises the dye for strong interaction with light - a property of the cyanines that has been exploited for use in laser spectroscopy, formulation of photographic emulsions, and numerous other applications. The interaction between surfactants and dyes is assessable through resulting changes in absorption and emission of the light-active compound, and this principle has permitted the use of the closely related Pinacyanol chloride in determining physical and chemical information of cationic surfactants, micelles, and vesicles. The dimer of 1,1'-Diethyl-2,2'-carbocyanine iodide also absorbs and this dimerization can be monitered by changes in the observed absorption wavelength of a sample.