In this report we have studied, the substitutional effect on photophysical properties of newly synthesized isomeric benzocoumarin-Sesamol Conjugates using absorption, steady-state fluorescence emission, and time-resolved emission measurements. The structural characterization of the synthesized dyes was carried out using FT-IR, 1H-NMR, 13C-NMR, and MS. The ground states are estimated using theoretical (ab-intio) experimental techniques. The excited state dipole moment was calculated using the solvatochromic method. Stoke's shift exhibits a redshift with an increase in solvent polarity for synthesized indicating a p-p* transition. The HOMO-LUMO energy gaps computed from density functional theory and absorption threshold wavelengths are found to be in good agreement with each other and also support intramolecular charge transfer (ICT). The Global chemical reactivity descriptor parameter and electrostatic potential (MESP) plots suggest that molecules have strong electrophilic and nucleophilic sites. The preliminary photophysical observations and results suggest that the fluorescent dyes can be considered as potential material for the construction of solar cells, fluorescent probes, and chemosensors.

Here we report a simple method for the synthesis of a D−π−A substituted bromomethyl coumarin derivatives 1-(6-Bromo-benzo[1, 3]dioxol-5-yloxymethyl)-benzo[f]chromen-3-one (1BDYMBC) and 4-(6-Bromo-benzo[1, 3]dioxol-5-yloxymethyl)-benzo[h]chromen-2-one (4BDYMBC) via a one-pot chemical reaction. The FT-IR, 1H-NMR, and MS results confirmed the corresponding structure of the synthesized dyes. The substitution effect, on optoelectronic properties was verified using experimental and theoretical techniques. The absorption and fluorescence spectra of fluorescent dyes were recorded in different solvents of different polarity. Stoke's shift exhibits a redshift with an increase in solvent polarity for all molecules indicating a π−π∗ transition. The ground state dipole moments of all fluorescent dyes are estimated theoretically from ab initio computations (integral equation formalism of polarizable continuum model) and experimentally from the solvatochromic method and the results are compared. The excited state dipole moments are estimated using solvatochromic correlations equation and results show that the excited state dipole moments are higher than the ground state dipole moments which suggests that, all fluorescent dyes are more polar in the excited state. The HOMO-LUMO energy gaps computed from density functional theory and absorption threshold wavelengths are found to be in good agreement with each other and also support intramolecular charge transfer (ICT). The chemical hardness of the molecules is determined and the chemical stability is discussed. Further, using DFT molecular electrostatic potential (MESP) plots, the electrophilic site and nucleophilic site which are useful in photochemical reactions were identified. Finally, all the preliminary observations and results suggest that the fluorescent dyes can be considered as potential candidates for fluorescent probes and for the construction of dye sensitized solar cell in future.