Browsing by Author "Yadav, Bhoopendra"
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PublicationArticle Conformational and vibrational investigations of L-Tryptophan zwitterion(Elsevier B.V., 2018) Yadav, R.A.; Yogesha, M.; Yadav, Bhoopendra; Santhosh, C.Theoretical computations of the molecular structures and vibrational parameters for all the possible conformations of L- Tryptophan in zwitterionic form have been carried out using the Gaussian 09 [DFT (B3LYP)] and GAR2PED softwares. The experimental IR and Raman data characterization and analysis have been made on the basis of the computed geometrical and vibrational parameters. The vibrational assignments of the experimentally observed vibrational bands have been proposed using the outcomes of the computed parameters. The geometrical parameters available in the literature and absence of C[dbnd]O stretching frequency in the IR spectrum suggest the molecule to exist in the zwitterionic form. Intramolecular H bonding is found between one O atom of the CO2 group and one H atom of the NH3 group. Intermolecular H bonding is expected between the H atom at the site N of the indole ring and O atom of another molecule and similarly, between one H atom of the NH3 group and O atom of another molecule. The charge transfer resulting in the molecule has been analysed using the HOMO–LUMO analysis. The electron density mappings of the iso-surfaces with the molecular electrostatic potentials (MEPs) have been carried out to obtain a number of data concerned with the charge density distribution, size, shape and site of chemical reactivity of the molecule. The region in the neighbourhood of the two O atoms of the CO2 group is the region of the most negative ESP in zwitterionic L-TRYP and is an active site for the neucleophilic attack. Similarly, the region in the neighbourhood of the three H atoms of the NH3 group is the region of the most positive ESP and is an active site for the electrophilic attack. © 2018PublicationArticle Conformational, structural and vibrational studies of estragole(Elsevier B.V., 2021) Yadav, Rohit Kumar; Yadav, Bhoopendra; Srivastav, Gaurav; Jha, Omkant; Yadav, R.A.Structural and conformational investigations were carried out at the B3LYP/6-311++G** level using the Gaussian 09 software. Vibrational spectra along with other related parameters like molecular geometries; APT charges etc were computed to analyze the experimentally measured Raman and IR spectra. In order to interpret the experimental spectra the potential energy distributions were computed using the GAR2PED software. Barrier heights for the [sbnd]OCH3, [sbnd]CH2CH[dbnd]CH2 and [sbnd]CH[dbnd]CH2 tops were estimated using the DFT and single top rotor theories. Vibrational contributions to the thermodynamic functions, namely, specific heat, entropy and free energy were determined. MEP, ESP plots and HOMO-LUMO energies were calculated using the results of the optimized structures of the three conformers of the estragole molecule. UV-vis spectrum was also investigated and interpreted. Comparative structural, active sites and vibrational investigations were made for all the three conformers. © 2021PublicationArticle DFT studies of molecular structures conformers and vibrational characteristics of sulfanilamide(Elsevier B.V., 2019) Srivastav, Gaurav; Yadav, Bhoopendra; Yadav, Rohit Kumar; Yadav, R.A.Molecular structures and vibrational parameters for all the four possible conformers of sulfanilamide were studied using Gaussian 09 software and PEDs were calculated using GAR2PED software. MEP and HOMO-LUMO energies were computed and NBO analysis was carried out. Optimized geometries possess Cs symmetry. Out of 51 normal modes, 26 modes are conformer sensitive, out of which 2 modes show frequency variation above 75 cm−1 in going from one conformer to another. Out of the 6 internal modes of NH2, 4 modes were found at lower frequencies for S-NH2 group compared to C-NH2 group, due to presence of intra-molecular O⋯H bonds in the SO2(NH2) group. Strength of nucleophilic attack is stronger with the H atoms of C-NH2 group compared to the H atoms of the S-NH2 group. Intra-molecular O⋯H bonds also lead to difference in corresponding geometrical parameters of S-NH2 and C-NH2 groups and difference in atomic charges at corresponding sites. © 2019 Elsevier B.V.PublicationArticle Experimental IR, Raman, and UV-Vis Spectra DFT Structural and Conformational Studies: Bioactivity and Solvent Effect on Molecular Properties of Methyl-Eugenol(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Yadav, Rohit Kumar; Yadav, Bhoopendra; Yadav, R.A.; Kostova, IrenaHighlights: What are the main findings? The ME molecule has 21 stable configurations. For all the tops (except =CH2), the barrier heights are of the same order, while the =CH2 top has a barrier height one order of magnitude higher. Like estragole and eugenol, ME also has the same Fermi doublets for the following modes: νs(–CH2) and 2 (Formula presented.) βs(–CH2); νs(CH3) and 2 (Formula presented.) δs(CH3). The ME molecule has three active sites. Vibrational analysis suggests that the solvents affect the internal modes of both OCH3 moieties strongly. What is the implication of the main finding? The methyl-eugenol molecule could be a good choice for the pharmacological applications The OCH3 moieties of methyl-eugenol play significant role in interaction with other molecules. Structural, conformational, and spectroscopic investigations of methyl-eugenol were made theoretically at the B3LYP-6-311++G**level. Experimental IR, Raman, and UV-vis spectra were investigated and analyzed in light of the computed quantities. Conformational analysis was carried out with the help of total energy vs. dihedral angle curves for different tops, yielding 21 stable conformers, out of which only two have energies below the room temperature relative to the lowest energy conformer. The effect of the solvent on different molecular characteristics was investigated theoretically. MEP and HOMO-LUMO analysis were carried out and barrier heights and bioactivity scores were determined. The present investigation suggests that the molecule has three active sites with moderate bioactivity. The solvent–solute interaction is found to be dominant in the vicinity of the methoxy moieties. © 2023 by the authors.PublicationArticle Experimental Raman, FTIR and UV-vis spectra, DFT studies of molecular structures and barrier heights, thermodynamic functions and bioactivity of kaempferol(Elsevier B.V., 2022) Yadav, Bhoopendra; Yadav, Rohit Kumar; Srivastav, Gaurav; Yadav, R.A.Molecular structures and vibrational parameters for the all the four possible conformers of kaempferol were investigated using Gaussian 09 and GAR2PED software. Raman and FTIR spectra of kaempferol were recorded in the regions 50–4000 cm−1 and 400–4000 cm−1, respectively and interpreted in the light of the computed quantities. Some of the modes were found to have conformer dependent frequencies, IR and Raman intensities and depolarisation ratios. The complex, broad and intense IR band in the range 2900–3500 cm−1 is explained to arise due to the four OH stretching and an overtone modes. The barrier heights for the OH tops against internal rotations have been determined. The UV–vis absorption spectrum was measured in the range 220–800 nm. MEP and HOMO-LUMO energies were computed for all the four conformers and NBO analysis was carried out. Thermodynamic functions of title compound have been carried out. Different bioactivity scores for this molecule were computed. © 2022PublicationArticle Experimental Raman, FTIR and UV-Vis Spectra, DFT Studies of Molecular Structures and Conformations, Barrier Heights Against Internal Rotations, Thermodynamic Functions and Bioactivity of Biologically Active Compound - Isorhamnetin(Taylor and Francis Ltd., 2024) Yadav, Bhoopendra; Yadav, Rohit Kumar; Srivastav, Gaurav; Yadav, R.A.Molecular structural, conformational and spectroscopic investigations on the isorhamnetin molecule have been carried out at the B3LYP/6-311++G(d,p) level. Experimental FTIR, Raman and UV–vis spectra have been recorded and analyzed in light of the computed quantities and potential energy distributions (PEDs). In addition, MEP, Iso-surface plot of ESP and HOMO-LUMO energies, the barrier heights for the internal rotations about different axes and different thermodynamic functions were computed. Moreover, the wavefunction properties like reduced density gradient and electron localization function were computed. To investigate the biological properties, the bioactivity scores were computed and the molecular docking was also performed. The planarity of the flavone skeleton was stabilized by intramolecular interactions of O16.H24, and O26…H22. The barrier heights for bound OH tops were three times than the free OH tops. The bond length of the C-C linkage was found to be the longest among all the C-C bonds. Out of 99 normal modes, only 66 normal modes were seen to be conformer dependent. The sites near the H and O-atoms of free OH groups are more effective for nucleophilic and electrophilic attacks. The HOMO-LUMO analysis suggests that the molecule is chemically soft. From the observed UV-Vis spectral analysis bathochromic shift was noticed. Thermodynamic functions varied non-linearly with temperature. The bioactivity scores and molecular docking suggest that the molecule is a bioactive molecule. The results of the present investigations made on the isorhamnetin molecule are reported for the first time. © 2023 Taylor & Francis Group, LLC.PublicationBook chapter Soft Perovskite Semiconductors for Future Optical Electronics(wiley, 2024) Yadav, Rashmi; Yadav, BhoopendraThis chapter investigates the non-linear optical properties of induced stained straddled-type InGaAsP/InP semiconductor-based nanoscale heterostructures by using the GAIN software package. We observed from the evaluated results a significant sound in the case of TE mode. Moreover, the non-linear optical properties such as optical gain, refractive index, differential gain, and antiguiding factor have been evaluated for compressive and tensile strain InGaAsP/InP single quantum well (SQW)-based lasing nano-heterostructures in TE and TM (Transverse magnetic) mode, and an optical gain increase was found as we increase the introduced strain value; the maximum gain with lasing wavelength can be controlled by varying the strain value. The maximum value of material gain has been obtained at a wavelength of 1.46 µm whenever tensile strain is introduced, while for the compressive strain, the maximum material gain value has been achieved at 1.41 µm lasing wavelength. Hence, the nano-structure studied in this work is very useful as a light source for the optical fiber-based communication system functioning in the NIR (near-infrared) region due to less attenuation. © 2024 Scrivener Publishing LLC.PublicationArticle Spectroscopic, structural and conformational investigations of the major constituent of the clove oil: Eugenol(Elsevier B.V., 2023) Kumar Yadav, Rohit; Yadav, Bhoopendra; Yadav, R.A.Molecular structures of the 12 possible conformers of eugenol were optimized at the B3LYP/6–311++G** level available with the Gaussian 09 software. IR and Raman spectra of eugenol were measured and analysed in light of the computed quantities. The interpretation of the IR spectrum in the OH stretching region suggested the existence of eugenol in the dimeric form. Five dimeric structures of the lowest energy monomeric conformer (C-I) were found to have energy difference below 300K. The complete observed IR and Raman spectra could be explained in terms of the computed spectra of the five lowest energy dimers of C-I. UV–vis absorption spectrum was measured in the range 200–600 nm and analysed with the help of computed parameters. Moreover, MEP plots and HOMO-LUMO analysis were carried out. Different computed quantities/ parameters for C-I and its 5 dimers are compared. In addition, barrier heights for different tops, thermodynamic functions and bioactive scores of the eugenol molecule were determined. © 2023 Elsevier B.V.PublicationArticle Vibrational spectra and molecular structure of sulfanilamide: IR and Low temperature Raman studies and DFT investigation of monomeric and dimeric forms(Elsevier B.V., 2021) Srivastav, Gaurav; Yadav, Bhoopendra; Yadav, Rohit Kumar; Yadav, R.A.Raman spectra of sulfanilamide were recorded at temperatures 80, 90, 120, 150 and 300 K in the range 50-4000 cm−1. The room temperature FTIR spectrum of this compound was investigated in the range 400−4000 cm−1. The molecular structures and vibrational parameters for the lowest energy conformer of sulfanilamideand its dimer were carried out at the B3LYP/6−311++G** levelusing the Gaussian 09 software and PEDs have been calculated using the GAR2PED software. Low temperature Raman spectra enabled to observe some modes which were not resolved at room temperature.The low temperature Raman spectra show splitting of bands around 1135 and 1595 cm−1 which could be associated with the (C)NH2---SO2(NH2) interaction, which is indicative of the existence of sulfanilamide in dimeric form. Based on the present investigation five Quantum Scaling Factors (QSFs) are proposed.These QSFs provide better agreement between the observed and computed scaled frequencies. © 2020 Elsevier B.V.PublicationArticle Vibrational spectra and molecular structure of sulfanilic acid: IR and low temperature Raman studies and DFT investigation of monomeric and dimeric forms(Elsevier B.V., 2023) Srivastav, Gaurav; Yadav, Rohit Kumar; Yadav, Bhoopendra; Yadav, R.A.Room temperature IR and Raman spectra, low temperature Raman spectra and UV–vis spectrum of sulfanilic acid (SA) were measured. Molecular structures of monomeric SA in the OH and zwitter-ion (ZI) forms and dimeric SA were optimized at the b3lyp/6-311++g** level using the Gaussian 09 software. Computations of APT charges, IR, Raman and UV–vis spectra and related quantities were also carried out. MEP, ESP plots and pictorial representations of the HOMO-LUMO were drawn using the optimized structures of the different forms of the SA molecule. Barrier heights were calculated for different tops using one dimensional potential energy scan versus dihedral angle at the same level of theory. The IR, Raman and UV–vis spectra were interpreted in light of the computed quantities. Thermodynamic functions were computed in the temperature range 100–600 K. Bioactivity scores of the SA molecule were also determined. The present investigation suggests that the SA molecule exists in the ZI form as a monomer and in the OH form as a dimer. Appearance of the intense and broad IR band in the range 2200 to 3300 cm−1 could be explained only in terms of the O[sbnd]H stretching mode of the dimeric form of SA. © 2022
