The role of molecular size in the excited state behavior of aminocoumarin dyes in restricted media--2: study of BC I in AOT-formamide reversed micelles.
Ground and excited state properties of a pre-twisted 7-diethylaminocoumarin dye (BC I) belonging to the family of coumarinyl benzopyrano pyridines are reported in isooctane-AOT-formamide reversed micelles. In reversed micelles, BC I, albeit soluble in formamide, is found to remain out of the polar solvent pool. But the photophysical properties of the probe dye are sensitive to the changes in the polarity of the interfacial region caused by increase in F0 = [formamide]/[AOT]. The spectroscopic properties and dynamics are indicative of dual emission due to the solubilization of the dye in two different environments (the nonpolar solvent and the interfacial region). Results of the steady-state fluorescence anisotropy experiments also support the presence of two different environments. The present study once again proves that molecular size is an important parameter in the study of the photophysical properties of the flexible aminocoumarin dyes in reversed micelles.