Estimation Of The Ground State And First Excited State Dipole Moment Of Styryl Dyes Based On 7-[(E)-2-(Phenyl)Vinyl]-2-(4-Methoxy) Phenylimidazo [1,2-A] Pyridine Nucleus By The Solvatochromic Method

The ground state ( ) and the excited state ( ) dipole moments of two styryl dyes were studied at room temperature in various organic solvents. The dipole moments ( ) were estimated from solvatochromic shifts of absorption and emission spectra as function of the refractive index (n) and dielectric constant ( ) using Bilot-Kawski, Bakshiev, Lippert Mataga, Kawaski-Chamma-Viallet and Reichardt Methods. Then in order to estimate a theoretical investigation, the dipole moments were calculated in the respective organic solvents with computational method (TDDFT/B3LYP). Intramolecular charge-transfer (ICT) and twisted intramolecular charge transfer (TICT) have been observed due to higher values of excited state dipole moment than ground state dipole moment. The results show that excited state dipole moments of dyes are higher than ground state dipole moments of styryl dyes. The small change in the dipole moments was found after the introduction of sulphar and methoxy group in the styryl dyes are observed. It is observed that dipole moment value of excited state (μe) is higher than that of the ground state in both the styryl dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.