# Study of solvent effects on the molecular structure and the reorganization energies of $4-nitro-4^\prime -dimethyl-aminoazobenzene$ using resonance Raman intensities

Biswas, Nandita and Umapathy, Siva (2001) Study of solvent effects on the molecular structure and the reorganization energies of $4-nitro-4^\prime -dimethyl-aminoazobenzene$ using resonance Raman intensities. In: Journal of Raman Spectroscopy, 32 (6-7). pp. 471-480.

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## Abstract

Resonance Raman spectroscopy was used to probe the effect of solvent polarity on the molecular structure and isomerization dynamics of $4-nitro-4^\prime -dimethylaminoazobenzene$ (DA). In addition, the influence of the polarity and the relaxation behavior of the solvent on the mode-specific vibrational and solvent reorganization energies was investigated. Raman spectra were recorded in solvents with different polarity parameters, n-hexane and benzene, using 11 excitation wavelengths in the range 450-550 nm, scanning every 10 nm using the tunable laser pulse output of an optical parametric oscillator. It was observed that the solvent polarity plays a major role in influencing the excited-state potential energy surfaces of DA. The plot of resonance Raman intensities versus excitation wavelength (Raman excitation profiles) of the Franck-Condon-active fundamentals of DA shows that in n-hexane, the locally excited state is more favorable than that in benzene where the charge-transfer state is more stable. The distortions along the N-N and C-N stretching vibrations of DA in n-hexane and benzene infer isomerization via rotation in n-hexane and inversion in benzene. The increase in solvent and vibrational reorganization energies with increasing solvent polarity parameter suggests greater distortion in the Franck-Condon excited state following photoexcitation.

Item Type: Journal Article The copyright belongs to John Wiley & Sons, Ltd. Division of Chemical Sciences > Inorganic & Physical Chemistry 20 Mar 2006 19 Sep 2010 04:24 http://eprints.iisc.ernet.in/id/eprint/5611