Spectroscopic Characterization of Heptamethine Cyanine Dyes for the Interaction with the CN- and F-

The selectivity and sensitivity of a benzoindolium heptamethine cyanine dyes toward CN- and F- in DMSO are described. These anions interact with Dye-1 and Dye-2 forming anion-Dye adducts, the formation of which was supported by the Pariser-Parr-Pople molecular orbital (PPP MO) calculation. The different optical responses in Dye-1 stimulated by addition of CN- (blue to pale yellow) and F- (blue to pink) allow simultaneous estimation of CN- and F-.