EXTERNAL IODINE ATOMS INFLUENCE OVER THE INTERSYSTEM CROSSING RATE OF A CYANINE IODIDE-ION PAIR IN BENZENE SOLUTION

The photochemical and photophysical properties of N,N'-dibutyltetramethylindocarbocyanine iodide {[TMIC]Bu+I-} in benzene solution were examined by absorption spectroscopy and flash photolysis on a picosecond time scale. In benzene solution, the dye iodide exists nearly exclusively as an ion pair. Under these conditions the absorption spectrum of the cyanine dye is perturbed by the iodide ion by a dispersion interaction. Irradiation of the cyanine iodide ion pair generates the triplet-state cyanine.