Near-Ir Electrogenerated Chemiluminescence of Tricarbocyanine Dyes in Micellar Systems

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Abstract
Two tricarbocyanine near-IR dyes containing the same (dimethyl naphthalindole) heterocyclic nuclei, IR144 and IR125, were studied in organic solvents, in water, and in the presence of certain surfactants. The anodic oxidation of IR144 produces electrogenerated chemiluminescence (ECL) in the presence of tri-n-propylamine as a coreactant in sodium dodecyl 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 the micelle system, the potential was shifted to a more positive potential, +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 potential did not change in water or surfactant solution. The absorption spectra indicated extensive dimerization for IR144 in aqueous solution, while IR125 showed little evidence of dimerization. For IR144, the 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 micelle ECL reactions should be useful in the design of new labels for ECL applications.

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