Experimental and Theoretical Approach to Estimate Electric Dipole Moments and Analysis of Preferential Solvation, Fluorescence Quenching of 4 NPMB Coumarin Molecule by Steady State Method.

The fluorescence and absorption characteristics of coumarin 1-(4-nitro-phenoxymethyl)-benzo[f]-chromen-3-one (4NPMB) at room temperature are examined in a mixture of acetonitrile (ACN) and tetrahydrofuran (THF) as well as in a few pure organic solvents. The influence of pure liquids on spectral characteristics is examined using various theories. Ground and excited state electric dipole moments were computed employing theoretical and Solvatochromic approaches. The redshift and excited electric dipole moment value of a molecule indicates that the molecule has gone through the intermolecular charge transfer (ICT). Kamlet-Taft suggests that the 4NPMB molecule integrates the solvent by its hydrogen bonding parameter rather than the dielectric parameter. From Catalan linear regression, we found that solvent acidity (SA) and the polarizability (SP) of a solvent have much more influence compared to solvent basicity (SB) and di-polarity (SdP) on a molecule. According to the preferential solvation investigation, tetrahydrofuran dominates the system up to the bulk molar fraction of 0.31. Acetonitrile thereafter takes over, as shown by the value of the preferential solvation constant ( $M_{12})$ . Fluorescence quenching of physiologically active fluorescent probe examined by using aniline as a quencher in various solvents. According to the fluorescence quenching investigation, the Stern-Volmer plot in solvents with varying dielectric constants exhibits a linear dependency, revealing that quenching responses are dynamic in nature. Different types of quenching associated with the reaction have been found, and their corresponding quenching parameters have been evaluated.