Photophysical Properties of 7-(diethylamino)Coumarin-3-carboxylic Acid in the Nanocage of Cyclodextrins and in Different Solvents and Solvent Mixtures

The photophysical properties of 7-(diethylamino) coumarin-3-carboxylic acid (7-DCCA) were studied in cyclodextrins (, , ,-CDs), different neat solvents and solvent mixtures by using steady state absorption, emission and time-resolved fluorescence spectroscopy. We have observed that with gradual increase in concentration of -CD the fluorescence quantum yield and lifetime decreased in a regular pattern whereas with gradual increase in concentration of -CD the fluorescence quantum yield and lifetime gradually increased. With addition of urea, the fluorescence quantum yield and lifetime of 7-DCCA in CDs increased. Binding constant calculation shows that 7-DDCA forms 1:1 complex with -CD and with -CD it forms 1:1 and 1:2 (guest:host) inclusion complex. We proposed that the dye molecule formed capping complex with -CD by means of hydrogen bonding and after addition of urea the hydrogen bonding network broke down and part of dye molecule entered inside the cavity of -CD. The photophysics of 7-DCCA was studied in dioxane-water mixture and ethylene glycol-acetonitrile mixture to know the effect of polarity and viscosity of the media. The photophysics of 7-DCCA was also studied in different neat solvents. It was found that the photophysics of 7-DCCA depended on the structural feature of the solvents and solvent mixtures.