The role of molecular size in the excited state behavior of aminocoumarin dyes in restricted media - 2: study of BCI 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-AQT-formamide reversed micelles. In reversed micelle s, BC I, albeit soluble in formamide, is found to remain out of the polar s olvent pool. But the photophysical properties of the probe dye are sensitiv e to the changes in the polarity of the interfacial region caused by increa se in F-0 = [formamide]/[AOT]. The spectroscopic properties and dynamics ar e indicative of dual emission due to the solubilization of the dye in two d ifferent environments (the nonpolar solvent and the interfacial region). Re sults of the steady-state fluorescence anisotropy experiments also support the presence of two different environments. The present study once again pr oves that molecular size is an important parameter in the study of the phot ophysical properties of the flexible aminocoumarin dyes in reversed micelle s. (C) 2000 Elsevier Science B.V. All rights reserved.