Photo physical properties of fluorescent organic compounds give an immense improved knowledge on characteristics of excited state that is beneficial to devise innovate molecules and understand their performance in particular applications. Coumarin derivatives have been extensively investigated in this regard. This article narrates steady state fluorescence quenching measurements of a coumarin derivative namely 3-hydroxy-3-[2-oxo-2-(3-oxo-3H-benzo[f]chromen-2-yl)-ethyl]-1,3-dihydro-indol-2-one (3HBCD) in a binary mixture of acetonitrile and 1,4-dioxane. Aniline is used as quencher. Fluorescence intensity is large in acetonitrile and decreases as the percentage of 1,4-dioxane in the solvent mixture increases. With modest quencher concentration a deviation towards the x axis is noticed in the Stern-Volmer (S-V) plots. This downward curvature is interpreted as due to the presence of 3HBCD in different conformers in the lowest energy level. Ground state intramolecular hydrogen bonding formation is observed due to the conformational changes in the solute. Figured estimations of various quenching parameters recommend that, while dynamic quenching prompts linearity in S-V plot at lower quencher concentration, increasing quenching efficiency with increasing medium viscosity suggests that reaction is not entirely controlled by material diffusion. Stern-Volmer constant increases with decreasing medium dielectric constant.

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Simple, effective, and eco-friendly sugar-based phase-selective gelators were synthesized at a low cost. They showed high gelling ability toward a wide range of solvents at lower concentrations (minimum gelation concentration ∼0.3%). Preliminary tests reveal that these low molecular weight organogelators can immediately and phase-selectively gel benzene, toluene, petrol, and kerosene in water at room temperature. We also identified G13 in toluene as the good gelator, and the corresponding organogel proficiently removes water-soluble dyes from their concentrated aqueous solutions. This efficient removal of toxic organic solvents and dyes from water suggests promising applications in removing organic substances from contaminated water resources. The thermoreversible gel exhibits effective rechargeability up to five cycles of burning and gelation, which imply the flame stability of the gel. Interestingly, these compounds had a high detection ability toward Cu2+ ions with a state change from gel to the solution. The physical justification for gelation mechanisms and the molecular interaction with metal ions were further confirmed by computational studies.

In an attempt towards understanding the relation between molecular structure-nonlinear optic activity (NLO) among heterocycles, with special reference to the identity, number and position of the heteroatom, semiempirical calculations were carried out. This paper reports the Non-linear optical properties of two heterocyclic compounds namely 3-[2-Oxo-2-(2-oxo-2H-chromen-3-yl)-ethylidene]-1,3-dihydro-indol-2-one (3OCEDI) and Quinolin-8-ol (QL). To understand the NonLinear Optical properties of coumarin dyes we computed dipole moment (μ), electronic polarizability (α), and the mean was first hyperpolarizability (βo) using B3LYP density functional theory method in conjunction with 6-31G(d, p) basis set.All the calculations were carried out in gas phase and in acetonitrile medium. The optimized geometry of both compounds shows a 3D helical structure. The results indicate that given the same number and type of atoms and double bonds in a molecule, linear conjugation excels over cyclic or crossed conjugation in enhancing hyperpolarizabilities and it seems to be far more critical than a chiral centre. KEYWORDS: NLO, 3OCEDI, QL, DFT, dipole moment, polarizability, hyperpolarizability

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