Study of Photophysical Properties on Newly Synthesized Coumarin Derivatives

Herein, we have studied the photophysical properties for three newly synthesized coumarin derivatives; 4-((2,6-dibromo-4-methylphenoxy)methyl)-2H-benzo[h]chromen-2-one (DMB), 4-((3,4-dihydro-6,7-dimethoxyisoquinolin-1-yl)methyl)-6-methyl-2H-chromen-2-one (DIM) and 4-((p-tolyloxy)methyl)-6-methoxy-2H-chromen-2-one (TMC). The absorption and emission spectra for above said molecules were recorded in different solvents at room temperature in order to calculate their ground and excited state dipole moments. The ground (μ _g ) and excited state dipole (μ _e ) moments of these coumarin derivatives were calculated using Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations by the solvatochromic shift method, which involves a variation of Stokes shift with the solvent dielectric constant and refractive index. Ground state dipole moments (μ _g ) were also calculated from the Guggenheim method using the dielectric constant and refractive index of the solute molecule. The value of ground state dipole moment obtained from these two methods is well correlated. Further, it is notified that the excited state dipole moment is larger than the ground state dipole moment for all three solute molecules. It inferred that the excited state for above said molecules is more polar than the ground state. The present investigations may shine in the design of nonlinear optical materials. Graphical Abstract The photophysical properties for novel coumarin derivatives were studied in different solvents.Ground and excited state dipole moments were estimated by the solvatochromic shift method. The excited state dipole moment is greater than the ground state dipole moment in systems studied. The excited state is more polar than the ground state. The present investigation may be shine in the design of non linear optical materials.

Photophysical Properties of a Novel and Biologically Active 3(2H)-Pyridazinone Derivative Using Solvatochromic Approach

Herein, we report photophysical properties of a novel and biologically active 3(2H)-pyridazinone derivative 5-(4-chloro-2-hydoxy-phenyl)-2-phenyl-2H-pyridazin-3-one [CHP] molecule using solvatochromic approaches. Absorption and fluorescence spectra of CHP molecule have been measured at room temperature in various solvents of different polarities. From this, it is observed that the positions, intensities and shapes of the absorption and emission bands are usually modified. Experimentally, the ground and excited state dipole moments are estimated using solvatochromic shift method which involves Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations. Theoretically, the ground state dipole moment was estimated using the Gaussian-09 program. The value of ground state dipole moment estimated using experimental and theoretical methods are well correlated. This inference that the molecular geometry is taken for CHP molecule under theoretical and experimental methods are similar. Further, we observed that the excited state dipole moment (μ _e ) is greater than the ground state dipole moment (μ _g ) which indicates that the excited state is more polar than the ground state. Furthermore, we have estimated an angle between the ground and excited state dipole moments. In addition, we have estimated the fluorescence quantum yield of CHP molecule using Rhodamine B as a standard reference in different solvents.

Analysis of Fluorescence Quenching for Newly Synthesized Biologically Active 3(2H)-pyridazinone Derivative by Aniline

Herein, we have studied the analysis of fluorescence quenching for newly synthesized biologically active 3(2H)-pyridazinone derivative 5-(5-bromo-2-hydroxy-phenyl)-2-phenyl-2H-pyridazin-3-one [BHP] by various concentrations of aniline using UV-Visible spectroscopy, fluorescence spectroscopy and time-correlated single photon counting technique in five different solvents namely, methanol, ethanol, propan-2-ol, dimethylsulfoxide and ethyl acetate at room temperature. The fluorescence intensity of BHP molecule decrease with increasing in the aniline concentration and it is studied using the Stern-Volmer relation. The obtained Stern-Volmer plots were found to be linear in all the five solvents. The various parameters responsible for the fluorescence quenching such as quenching rate parameters (k _q ), diffusion rate parameter (k _d ) and the probability of quenching per encounter (p) were experimentally calculated in all five solvents. An activation energy of quenching (E _a ) was calculated using the values of activation energy of diffusion (E _d ) and p. It was found that the values of E _a are greater than E _d in all five solvents studied. Further, it is inferred that the fluorescence quenching reactions in BHP molecule are more significantly affected by activation energy processes.

Biogenic and chemogenic synthesis of TiO2NPs via hydrothermal route and their antibacterial activities

Novel biogenic and chemogenic sources were used for the synthesis of TiO₂NPs with size of NPs for biogenic smaller than chemogenic. From Agar well diffusion method the biogenic synthesized TiO₂NPs show more effective antibacterial activities.