NEAR-IR ELECTROGENERATED CHEMILUMINESCENCE OF TRICARBOCYANINE DYES INMICELLAR SYSTEMS

Two tricarbocyanine near-IR dyes containing the same (dimethyl naphtha lindole) heterocyclic nuclei, IR144 and IR125, were studied in organic solvents, in water, and in the presence of certain surfactants. The a nodic oxidation of IR144 produces electrogenerated chemiluminescence ( ECL) in the presence of tri-n-propylamine as a coreactant in sodium do decyl sulfate surfactant solution or in MeCN/DMSO (2:1 v/v) solution. The one-electron oxidation of IR144 generated the corresponding fairly stable radical cation at +0.48 V vs Ag/AgCl in MeCN/DMSO (2.1). In th e micelle system, the potential was shifted to a more positive potenti al, +1.1 V vs Ag/AgCl, as found by differential pulse voltammetry. The ECL intensity for IR125 was much weaker than that of IR144. and the p otential did not change in water or surfactant solution. The absorptio n spect-ra indicated extensive dimerization for IR144 in aqueous solut ion. while IR125 showed little evidence of dimerization. For IR144. th e fluorescence intensity in water decreased dramatically when compared to both organic solvents MeOH and MeCN. In all the aqueous surfactant solutions. the fluorescence intensity is partially restored. These mi celle ECL reactions should be useful in the design of new labels for E CL applications.