Complex formation between sensitizing dyes and stabilizers: A possible contributing factor in supersensitization

We have provided evidence, from fluorimetric titration and analysis of the spectral distribution of fluorescence, that representative symmetrical cyan ine dyes, DTCI and DTDCI, form 1:1 complexes with photographic stabilizers, 2-methylbenzimidazole (MeBz), 2-mercaptobenzoxazole (MBO), tetraazaindene (TAI), and the conjugate anions of the latter two compounds, in solution. A M1 semi-empirical and molecular mechanics calculations are introduced to in terpret these results. Complex formation is consistent with the reported ro le of these stabilizers in supersensitization given the following possibili ties: (1) the complexes may be adsorbed to silver halide surfaces in prefer ence to free dye; (2)incorporation of the complex can disrupt a J-aggregate of the dye, with concomitant decrease in recombination probability in the aggregate; and, (3) insofar as computations suggest a partial charge transf er character to the complexes, they may be energy trapping sites on the gra in surface, where electron injection into the grain is facilitated.