Solvent effects on the dipole moments and photo physical properties of laser dye

Abstract

The absorption and emission spectra of fluorescent laser dye namely, 4,4”’-bis-2-butyyloctyl-oxy)-P-quaterphenyl have been recorded at room temperature in solvents of different polarities. The exited state dipole moments (µ_e) have been estimated from Lippert’s, Bakhshiev’s and Kawski-Chamma-Viallet’s equations using the variation of Stoke’s shift with the solvent dielectric constant and refractive index. The geometry of the molecule has been fully optimized and the µ_g has also been calculated theoretically by Gaussian 03 software using B3LYP/6-31g* level of theory. The µ_g and µ_e have been calculated by means of solvatochromic shift method. It has been observed that µ_e is higher than µ_g, indicating a substantial redistribution of the π-electron densities in a more polar excited state for the selected laser dye. Further, the changes in the dipole moment (µ) has been calculated both from solvatochromic shift method and microscopic empirical solvent polarity parameter (E) and values are compared.