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Effect of Polar Solvents on Absorption Spectra of Coumarin 1 : PCM-TDDFT Study

M. Ramegowda and H. R. Sreepad

Density functional theory (DFT/ Time dependent density functional theory (TDDFT) calculations have been carried out to study the electronic structure and the exited state properties of coumarin 1 dye. The exited state properties have been investigated with inclusion of solvent effect. The B3LYP functional with a cc-pVDZ basis set have been used to compute transition energies. The solvent effects have been described within the polarizable continuum model (PCM). Ground-state geometries are optimized using DFT with B3LYP functional combined with cc-pVDZ basis sets. Vertical absorption energy calculations characterize the lower singlet excited states both in gas phase and in solvents. A large red-shift of the absorption maximum in the polar solvents suggests an intra-molecular charge transfer character of the excited state. The absorption maximum both in gas phase and in polar solvents is discussed in terms of electrostatic interaction energy, oscillator strength and dipole moment.