Synthesis, Spectral Characterization and Photoluminescence of 3-chloro-6-methoxy-2-(methylsulfanyl)quinoxaline in Different Solvents: An Experimental and Theoretical Investigation Using DFT.

In the present work, we synthesized 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ) using a microwave-assisted synthesis method. The physicochemical structural analysis of the synthesized compound utilizing 1H-NMR, 13C-NMR, and FT-IR spectroscopy techniques. The photophysical properties of 3MSQ was examined through absorption and fluorescence spectroscopy. Spectroscopic analyses revealed a bathochromic shift in both absorption and fluorescence spectra, attributed to the π → π* transition. Ground and excited state dipole moments was experimentally determined using the solvatochromic shift method, employing various correlations such as Lippert's, Bakhshiev's, Kawski-Chamma-Viallet's equations, and solvent polarity parameters. Our findings indicate that the excited state dipole moments exceed those of the ground state, suggesting increased polarity in the excited state. Further, the while detailed bond length, bond angles, dihedral angles, Mulliken charge distribution, ground state dipole moments and HOMO-LUMO energy gap estimated through ab initio computations using Gaussian-09W. The value of energy band gap obtained from both the methods are in good agreement. Furthermore, employing DFT computational analysis, we identified reactive centers such as electrophilic and nucleophilic sites using molecular electrostatic potential (MESP) 3D plots. Additionally, CIE chromaticity analysis was performed to understand the photoluminescent properties of 3MSQ. The insights derived from these analyses contribute to a better understanding of the molecule's electronic structure, photophysical properties, and solute-solvent interactions, thus providing valuable information regarding its behaviour and characteristics under diverse conditions. These results contribute to a comprehensive understanding of the molecular structure and properties of 3-chloro-6-methoxy-2-(methyl sulfanyl) quinoxaline (3MSQ).

Rotational Diffusion of Medium Sized 7-[Diethylamino]-2H-1-Benzopyran-2-One Molecule in Alcohols: Study of Temperature and Solvent Viscosity Effect.

The rotational re-orientations times of the 7-[diethylamino]-2H-1-benzopyran-2-one (7-DHB) dye molecule have been examined in ethanol and octanol solvents when macroscopic solvent viscosity parameter is varied by varying the temperature, by employing the steady-state fluorescence depolarisation and Time-Correlated Single Photon Counting (TCSPC) techniques. Experimental observation shows that 7-DHB probe is experiencing higher friction in octanol compared to ethanol and rotates slower by a factor of 7.3. The hydrodynamic Stokes Einstein's Debye theory (SED) with a stick, slip boundary conditions parameters, quasi-hydrodynamic models (Dote-Kivelson-Schwartz and Geirer-Wirtz) were used to determine mechanical friction and found an interesting towards super slip trend. Dielectric frictional theories of point dipole, Nee-Zwanzig and van der Zwan-Hynes both models fail to describe experimentally observe dielectric friction trends. Evidently, both hydrodynamic and dielectric models failed to explain the examined behavior, even in the qualitative way in alcohols.

An Experimental and Theoretical Test of Dielectric Friction Models Using Rotational Diffusion of 7-Diethylamino-2-H-1-Benzopyran-2-One in Non-associative Solvents.

The rotational re-orientations times of the 7-DHB dye molecule have been examined in non-associative solvents (DMSO and Octanenitrile) by varying the temperature, by employing the Steady-State Fluorescence Depolarisation and Time-Correlated Single Photon Counting (TCSPC) techniques. Rotational re-orientations time values in DMSO are found larger by a factor of 1.136 than octanenitrile, which indicates that 7-DHB laser dye is experiencing higher friction in DMSO than octanenitrile. To determine mechanical friction Stokes Einstein's Debye theory (SED) -with a stick, slip boundary conditions parameters are used and found an interesting super slip trend. Point dipole models as Nee-Zwanzig (NZ) and van der Zwan-Hynes (ZH) fail to explain experimental dielectric friction observed trends. Alavi-Waldeck model successfully explains the observed dielectric friction trend in non-associative solvents.

Electronic Structure, Optical Properties and Quantum Chemical Investigation on Synthesized Coumarin Derivative in Liquid Media for Optoelectronic Devices.

The newly synthesized 3,3'-((3-bromo-4-methoxyphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one) (3-BMH) derivative have been investigated in a selected number of organic solvents having different polarity and refractive index at room temperature. From the absorption and emission spectra of the synthesized derivative in studied solvents showed bathochromic shift in both the cases (Uv-vis and emission spectra), the ground state dipole moment (µg) and excited state dipole moment (µe) were obtained by implementing [Chamma-Kwaski-Villate, Bakhshiev, Lippert-Mataga, McRay and Suppan] solvatochromic shift techniques depending on solvent polarity parameters. The larger dipole moment value is observed in the excited state as compared to the ground state dipole moment and this discrepancy in the dipole moment value is due to polar nature of the molecule. From the results of both experimental and theoretical energy gap is found to 3.14 eV in average, from this, it can be concluded that the 3-BMH molecule showed a good agreement with the semiconducting material bandgap so that the 3-BMH molecule can be used as a potential material for the optoelectronic application. Also, from results of quantum chemical studies, the electrostatic potential maps studies reveal the molecule is how much stable it describes the defining reactivity of the molecule towards positively and negatively charged reactants, size, shape, the location of nucleophilic and electrophilic sites. Further, the optoelectronic properties were investigated the CIE, CRI, color purity and CCT results of the 3-BMH in all studied solvents revels that this compound exhibits blue emission (National television standard committee system (NTSC) for the ideal blue chromacity coordinate 0.14, 0.08) and from the CIE results show the color emission of the molecule in order to design the desired OLED device application.

Solvent Dependence on Structure and Electronic Properties of 7-(Diethylamino) - 2H -1- Benzopyran-2- one (C-466) Laser Dye.

In this work, we studied influences on the absorption and fluorescence emission spectra of coumarin-4066 (C-466) with different solvent polarity scale. The spectral shifts reflect the effect of the equilibrium solvents association across the energized solute particle, which adjusts inertially as a result of quick charge realignment upon radiative deactivation to the lowest electronic state. The dipole moments of C-466 are determined by employing the Bakhshiev, Kawski-Chamma-Viallet, Lippert-Mataga and McRae relations. The results from all these methods are, excited state dipole moment of C-466 is higher than the ground state dipole moments and which indicates molecule is less polar in the ground state. Theoretical analysis was also carried out by Density Functional theory (DFT and TD -DFT) employing the BECKE-1998 (exchange)/STO-6G basic set in ethanol solvent and in vacuum medium. The HOMO-LUMO, Solvent Accessible Surfaces (SAS) and Molecular Electrostatic Potential (MEP) were analysed to acquire additional knowledge of the molecular arrangement and electronic properties of C-466. These photophysical properties suggest delineation can be mauled for laying out new luminescent tests for various solvents microenvironment.

Investigations of adsorption and photoluminescence properties of encapsulated Al-ZnO nanostructures: Synthesis, morphology and dye degradation studies.

This study focuses on the solution combustion approach to examine the nanostructures of undoped and doped ZnO with different concentrations of Al (0.1 % and 0.2 %). Various physical techniques were utilized to characterize the synthesized nanoparticles. X-ray diffraction (XRD) revealed the crystalline materials, while scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) findings confirmed the products with particle size and the insertion of Al into the ZnO lattice. Fourier-transform infrared spectra (FTIR) confirmed the presence of different functional groups in the obtained material. The results indicate that Al-doped ZnO (Al-ZnO) nanoparticles show promising properties for optoelectronics and photoluminescence. Photoluminescence analysis indicated that an increase in Al3+ (0.2 %) concentration resulted in a decrease in peak intensity and an increase in the full width at half maximum. The band gap was calculated using the Taucs plot. The study also highlights the effectiveness of Zn1-xAlxO nanostructures in degrading organic pollutants, particularly in adsorbing Malachite Green (MG) dye. Among the samples, the 0.2 % Al-doped ZnO exhibited superior dye degradation efficiency due to its enhanced adsorption capacity and smaller particle size, as evidenced by multilayer adsorption capacity and chemisorption during the degradation process. This study provides valuable insights into the potential applications of Al-doped ZnO nanoparticles in various environmental and technological fields, emphasizing their significance in the degradation of organic pollutants.

Synthesis, photophysical, quantum chemical investigation, linear and non-linear optical properties of coumarin derivative: Optoelectronic and optical limiting application.

In order to develop a new photostable, light emitting and highly efficient synthesized material to exhibit display property and non-linear optical active materials with good band gap energy, we have synthesized molecule via simple catalytic method. The photophysical property of studied molecule in various organic solvents having different polarity exhibited considerably acceptable results. The results of quantum yield, lifetime and large Stoke shift shows the compound is a good promising candidate for the laser dyes and light emitting diode color filters. The energy band gap was determined by both experimentally and theoretically which is found to be an average of 3.2 eV which is well matched to the semiconducting materials band gap. The non-linear optical absorption properties of the synthesized molecule are dissolved in suitable solvents had been investigated using Z-scan technique. We have determined the sign and magnitude of nonlinear absorption coefficient by the method of open aperture Z-scan setup using an Nd: YAG continuous wave laser at 532 nm. The open aperture Z-scan profiles clearly demonstrate the presence of reverse saturable absorption kind nonlinearity in the investigated compound and are due to the two-photon absorption. Results of the non-linear optical studies confirm that the studied compound is more latent applications for optical limiting in continuous wave regime. Further, the optoelectronic properties were investigated the international commission on illumination, color rendering index, color purity, and correlated color temperature is results of the studied molecule in all studied solvents revels that this compound exhibits blue to cyan color and is suitable for organic light emitting diode which can be preferably used for daylight applications.

Solvent effects on the absorption and fluorescence spectra of coumarins 6 and 7 molecules: determination of ground and excited state dipole moment.

Absorption and fluorescence emission spectra of coumarins 6 and 7 were recorded in solvents with different solvent parameters, viz., dielectric constant epsilon and refractive index n. The fluorescence lifetime of these dyes were measured in butanol at higher values of viscosity over temperature. Experimental ground and excited state dipole moments are determined by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was determined that dipole moments of the excited state were higher than those of the ground state in both the molecules.

Rotational diffusion and solvatochromic correlation of coumarin 6 laser dye.

Rotational diffusion of coumarin 6 (C6) laser dye has been examined in n-decane and methanol as a function of temperature. The rotational reorientation of this probe has been measured in these solvents. It is observed that the decrease in viscosity of the solution is responsible for the decrease in the rotational relaxation time of the probe molecule. The molecule C6 has long reorientation times in n-decane solvent as compared to methanol over all temperatures. It is found that the coumarin 6 rotates slower in n-decane than in methanol especially at higher values of viscosity over temperature. Two methods are chosen to determine the ground state and excited state dipole moments. The change in dipole moments is estimated from Bakhshiev-Chamma-Viallet equations and, the ground and excited state dipole moments from Kawski et al. equations, by using the variations of the Stokes shifts with the dielectric constant and refractive index of the solvent. Our results are quite reliable which are solvatochromic correlation obtained using solvent polarity functions. The reported results show that excited state dipole moment is greater than ground state dipole moment, which indicates that the excited state is more polar than the ground state.