Bhawani Joshi | Tribhuvan University (original) (raw)

Papers by Bhawani Joshi

Research paper thumbnail of A Theoretical Study on Charge Transfer and Hyperpolarizability of (S)-2-amino-3-(3,4-dihydroxyphenyl)-2-methyl-propanoic Acid

Journal of Nepali Physical Society, Dec 13, 2022

The DFT approach was used to investigate the antihypertensive molecule (S)-2-amino-3-(3,4-dihydro... more The DFT approach was used to investigate the antihypertensive molecule (S)-2-amino-3-(3,4-dihydroxyphenyl)-2methyl-propanoic acid at the B3LYP/6-311++G(d,p) level of theory. The electron-hole analysis of three excited states has been performed, in which the maximum charge transfer length (2.727Å) has been calculated for the first excited state and the minimum for the third excited state (1.626 Å). On the other hand, the electron-hole overlap is found to be almost negligible for the first excited state and it is found to be maximum for the second excited state. The variation of thermodynamic properties with temperature is studied. The correlation graphs are obtained between the thermodynamic quantities (heat capacity, enthalpy, entropy) and temperature with a very high value of R 2 (>0.99). The values of dipole moment, mean polarizability, anisotropy of polarizability, first hyperpolarizability and second hyperpolarizability are found to be 3.5250 Debye, 12.6980×10-24esu, 19.8162×10 −24 esu, 0.9017×10 −30 esu and-0.0412×10 −35 esu, respectively. These values are higher than the value of urea.

Research paper thumbnail of Molecular interactions and vibrational properties of ricobendazole: Insights from quantum chemical calculation and spectroscopic methods

Journal of Molecular Structure, 2021

Abstract The structural, spectroscopic (FT-IR and FT-Raman), and physicochemical properties of ri... more Abstract The structural, spectroscopic (FT-IR and FT-Raman), and physicochemical properties of ricobendazole (RBZ) has been presented with the help of combined experimental and computational approaches. A comparison between the observed and simulated spectra show good agreement with each other. The conformational analysis was performed around eight flexible bonds to predict the most stable conformers, by employing density functional theory (DFT) at B3LYP/6–311++G(d,p) level. The chemical reactivity has been demonstrated in terms of frontier molecular orbitals (HOMO-LUMO) energy gap, molecular electrostatic potential (MEP) surface, and global reactivity. The local reactivity descriptors explored an idea about the donor/acceptor/free radical reactive sites present in the molecule. Natural bond orbital (NBO) analysis was performed to study the interactions between bonding and antibonding orbitals. The intramolecular hydrogen bonding interactions were demonstrated using QTAIM theory. Binding sites against three targets such as Poly [ADP-ribose] polymerase-1, MAP kinase p38 alpha, and Adenosine A2a receptor were identified by molecular docking analysis as RBZ is believed to inhibit against them.

Research paper thumbnail of Computational evaluation on molecular stability, reactivity, and drug potential of frovatriptan from DFT and molecular docking approach

Computational and Theoretical Chemistry, 2020

Molecular stability, fundamental chemical reactive sites, global reactivity descriptors in frovat... more Molecular stability, fundamental chemical reactive sites, global reactivity descriptors in frovatriptan molecule have been investigated by using computational evaluation and molecular docking approach. The density functional theory has been employed with standard functional B3LYP/6-311++G(d,p). The possible minimum energy structure has been predicted by implementing one-dimensional potential energy surface (PES) scan. The charge delocalization for stability of the molecule with natural bond orbital (NBO) analysis and molecular electrostatic potential (MEP) surface analysis to observe the active region for further chemical reaction with surrounding species have been performed. The chemical reactivity and hardness of the molecule in terms of HOMO-LUMO energy gap (ΔE L-H) have been implemented in terms of reactivity parameters. The potential use of frovatriptan as non-linear optical (NLO) material and its thermodynamical studies have also been performed. Moreover, the molecular docking with a predicted target has been performed to check the binding interaction as well as sites of the molecule. 2. Computational details Computational evaluation of the title compound has been carried out by using the Gaussian 09 software package [10]. The optimization has been performed by employing the default settings in the Gaussian

Research paper thumbnail of A comparative computational study on molecular structure, NBO analysis, multiple interactions, chemical reactivity and first hyperpolarisability of imatinib mesylate polymorphs using DFT and QTAIM approach

Molecular Simulation, 2013

ABSTRACT Imatinib, a phenylaminopyrimidine compound is a therapeutic drug for treatment of chroni... more ABSTRACT Imatinib, a phenylaminopyrimidine compound is a therapeutic drug for treatment of chronic myelogeneous leukaemia and gastrointestinal stromal tumours. It is well known that imatinib mesylate (ImM) exists in two polymorphic forms alpha and beta. In this work, a computational study on molecular properties of ImM polymorphs is presented using density functional theory, B3LYP functional and 6-311G(d,p) as basis set. Natural bond orbital analysis is carried out to investigate the various conjugative and hyperconjugative interactions within the molecule and their second-order stabilisation energy (E-(2)). The local nucleophilic reactivity descriptors such as Fukui functions (f(k)(-)), local softness (s(k)(-)) and electrophilicity indices (omega(-)(k)) analyses are carried out to determine the reactive sites within the molecule. To determine strength and nature of intra-and intermolecular interactions, topological parameters as electron density (ED) (rho(BCP)), Laplacian of ED (del(2) rho(BCP)) and total electron energy density (H-BCP) at bond critical points have been analysed by 'quantum theory of atoms in molecules' in detail. The computed first hyperpolarisability (beta(0)) for both forms of ImM molecule (10.927 and 10.354 x 10(-30) esu) suggests that the investigated molecule is an attractive object in future for non-linear optical properties. Molecular electrostatic potential surface of ImM has been mapped to predict the inhibitory activity and binding affinity with a panel of protein tyrosine kinases.

Research paper thumbnail of Molecular structure and quantum descriptors of cefradine by using vibrational spectroscopy (IR and Raman), NBO, AIM, chemical reactivity and molecular docking

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021

This study aims to investigate the structural and vibrational features of cefradine (the first-ge... more This study aims to investigate the structural and vibrational features of cefradine (the first-generation cephalosporin antibiotic) based on spectroscopic experiments and theoretical quantum chemical approach. The fundamental structural aspects of cefradine have been examined based on optimized geometry, spectroscopic behavior, intermolecular interaction, chemical reactivity, intramolecular hydrogen bonding, and molecular docking analysis. The most stable minimum energy conformer of the title molecule was identified by performing a one-dimensional potential energy surface scan along the rotational bonds at B3LYP/6-311++G (d,p) level of theory. The vibrational features of the molecule and information about the coupled modes were predicted. The chemical reactivity and stability of all the possible conformers of cefradine were estimated based on the HOMO-LUMO energy gap and NBO approach. The overall picture of accumulation of charges on individual atoms of the molecule was predicted by molecular electrostatic potential (MEP) surface map which in turn identifies the nucleophilic and electrophilic region or sites. The quantitative analysis of electrophilicity and nucleophilicity indices was done by Hirshfeld charge analysis and it was found that N8 atom is the most prominent site for nucleophilic attack while C14 atom is feasible for electrophilic attack. QTAIM study has also been performed to investigate the nature and strength of hydrogen bonding interactions. Besides, molecular docking studies were performed to examine the active binding residues of the target.

Research paper thumbnail of First principle study of chlorobenzene

Himalayan Physics, 2019

Chlorobenzene is a colourless flammable liquid used widely as a common solvent in the manufacture... more Chlorobenzene is a colourless flammable liquid used widely as a common solvent in the manufacture of other chemicals. In this communication, structural, electronic and vibrational study on chlorobenzene using Gaussian 09 program package employing B3LYP/6-31 G level of theory have been presented. The calculated IR and Raman spectra have been analyzed with the potential energy distribution. UV-Visible spectra taken in both the gaseous and solvent phase employing B3LYP/6-31G(d,p) level of theory have been given. The electronic transition between the frontiers energy levels together with their gap energy have analyzed.

Research paper thumbnail of Electronic, Thermodynamic Properties, Nonlinear Optical Responses, and Molecular Docking Studies on Cephalexin

Journal of Institute of Science and Technology

The topology analysis of electron localization function (ELF), localized orbital locator (LOL), t... more The topology analysis of electron localization function (ELF), localized orbital locator (LOL), the study of nonlinear optical properties, thermal properties, and biological activities of cephalexin have been performed using DFT/B3LYP and employing 6-311++G(d,p) basis sets. The Mulliken atomic charge on atoms has been calculated. The quantities describing nonlinear optical (NLO) properties like molecular polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) were comparable to the values of urea. The computed value of the second hyperpolarizability was found to be negative, which is an important feature for the system of controllable NLO devices. The thermodynamic properties like heat capacity (S), enthalpy (H), and entropy (S) are positively correlated with the temperature. Further, the title molecule shows good potentiality for binding with the selected target protein matrix metalloproteinase-2.

Research paper thumbnail of Quantum Chemical Calculation and DFT Study of Sitagliptin: Insight from Computational Evaluation and Docking Approach

Journal of Nepal Physical Society, 2020

This study aims to explore the structural and chemical behavior of sitagliptin using density func... more This study aims to explore the structural and chemical behavior of sitagliptin using density functional theory (DFT). The chemical reactivity has been studied in terms of MEP, HOMO-LUMO energy gap, Hirshfeld charge, and global and local reactivity descriptors. Thermodynamic parameters like entropy, enthalpy and specific heat capacity and, nonlinear optical (NLO) properties have been analysed. Higher value of the first hyperpolarizability than that of urea show its potential use as NLO material. Intra-molecular Hydrogen bonding and topological parameters at the bond critical point (BCP) of title molecule have been studied by using the quantum theory of atoms in molecules (QTAIM) approach. The bond of 2.3777 Å between H42…N11 is noticed to be strongest one. The pharmacological behavior and protein-ligand interaction of the title molecule have been investigated in terms of drug-likeness and molecular docking which motivates that the amine and carbonyl group bind with the amino acid of ...

Research paper thumbnail of Topological and Reactivity Descriptor of Carisoprodol from DFT and Molecular Docking Approach

Journal of Institute of Science and Technology

This study aims to investigate the optimized structure and optimized parameters of carisoprodol f... more This study aims to investigate the optimized structure and optimized parameters of carisoprodol from the DFT/B3LYP/6-31G(d,p) level of theory. The molecular electrostatic potential (MEP) map signifies that the positive potential across hydrogen of the amine group (NH2) and the negative potential around the carbonyl groups (C=O). HOMO-LUMO energy gap was found to be 8.1064 eV. The global and local reactivity parameters describe the possible chemical reactive sites in the molecule. The topological analysis of the electron localization function (ELF) and localized orbital locator (LOL) revealed that the charge localization around hydrogen atoms. The hyper-conjugative interaction between donor and acceptor orbital showed that the interaction LP(2) O4→ σ*(O2-C16) plays a vital role in the molecular stability. The molecular docking simulation encircles that the carisoprodol behaves as a good inhibitor with the target protein, Tyrosine-protein kinase ABL.

Research paper thumbnail of Measurement of natural background radiation level in Darchula district, Nepal

Scientific World

Natural background radiation level within Darchula district of Nepal was measured using a simple ... more Natural background radiation level within Darchula district of Nepal was measured using a simple portable Geiger-Müller counter. Data were collected along six different directions at different places (three-five places) of the sample sites of the district and was averaged. The average data value with their standard deviation was used for analysis. In this study, the maximum radiation counts of 51.16 2.30 CPM were reported at Satan and the minimum counts of 25.96 2.30 CPM at Gokuleshwar. The observed radiation level of the Darchula district shows that the district is below the radiation risk level (nearly 100 CPM).

Research paper thumbnail of Chemical Reactivity, Dipole Moment and First Hyperpolarizability of Aristolochic Acid I

Journal of Institute of Science and Technology, 2016

Aristolochic acids (AAs) have been used in the treatment of oedema in Chinese herb medicine since... more Aristolochic acids (AAs) have been used in the treatment of oedema in Chinese herb medicine since long ago. In this paper, molecular electrostatic potential, chemical reactivity and non linear optical properties of aristolochic acid I (AA I) have been analyzed using density functional theory employing 6-311++G(d,p) basis set. The chemical reactivity of the molecule has been explained with the help of chemical reactivity descriptors, molar refractivity and the molecular electrostatic potential surface (ESP). The calculated dipole moment and first order hyperpolarizability show that the molecule possesses non-linear optical property.

Research paper thumbnail of A combined experimental (IR, Raman and UV-Vis) and quantum chemical study of canadine

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 4, 2017

Plant based natural products cover a major sector of the medicinal field, as such focus on plant ... more Plant based natural products cover a major sector of the medicinal field, as such focus on plant research has been increased all over the world. As an attempt to aid that research, we have performed structural and spectroscopic analysis of a natural product, an alkaloid: canadine. Both ab initio Hartree-Fock (HF) and density functional theory (DFT) employing B3LYP using 6-311++G(d,p) basis set were used for the calculations. The calculated vibrational frequencies were scaled and compared with the experimental infrared and Raman spectra. The complete vibrational assignments were made using potential energy distribution. The structure-activity relation has also been interpreted by mapping electrostatic potential surface and evaluating the reactivity descriptors, which are valuable information for quality control of medicines and drug-receptor interactions. Natural bond orbital analysis has also been performed to understand the stability and hyperconjugative interactions of the molecul...

Research paper thumbnail of Conformational, Chemical Reactivity, Thermodymanic Properties and the Sem Study of Yohimbine Hydrochloride

We have presented a study on structural conformation of yohimbine hydrochloride using density fun... more We have presented a study on structural conformation of yohimbine hydrochloride using density functional theory (DFT) method. A short description about the surface morphology with scanning electron microscopy imaging has been included. Correlation between different thermodynamic properties with variation in the temperature has been given. The global and local chemical reactivity descriptors have been calculated, from which nucleophilicity and electrophilicity of the given atomic sites in the molecule can be known.

Research paper thumbnail of Structure, MESP and HOMO-LUMO study of 10-Acetyl- 10H-phenothiazine 5-oxide using vibrational spectroscopy and quantum chemical methods

BIBECHANA, 2012

In this communication, we have presented the geometry optimization, complete vibrational study wi... more In this communication, we have presented the geometry optimization, complete vibrational study with potential energy distribution (PED) and frontier orbital energy gap for the 10-Acetyl-10H-phenothiazine 5-oxide (APTZ) molecule using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method employing 6-311++G(d,p) basis set. The calculated IR and Raman spectra with their intensities, molecular electrostatic potential (MESP) surface and highest occupied molecular orbital (HOMO) - lowest unoccupied molecular orbital (LUMO) plot have been given. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7151 BIBECHANA 9 (2013) 38-49

Research paper thumbnail of Synthesis, characterization, magnetic properties and gas sensing applications of ZnxCu1−xFe2O4 (0.0≤x≤0.8) nanocomposites

Materials Science in Semiconductor Processing, 2014

In the present work Zn x Cu 1 À x Fe 2 O 4 nanocomposites were synthesized with a wide compositio... more In the present work Zn x Cu 1 À x Fe 2 O 4 nanocomposites were synthesized with a wide composition range (0.0 rx r0.8 in the steps of x ¼ 0.2) using a sol-gel method and thin films were fabricated using a spin-coating process. The synthesized materials were analyzed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, differential scanning calorimetry, UV-visible absorption and infrared spectroscopic techniques for their appropriate characterization. The XRD revealed the cubic spinel structure for each composition and the minimum crystallite size was found to be 10.4 nm. In order to study the thermodynamics during the synthesis, pre-and post-annealed materials were analyzed. An influence of the zinc on the magnetic properties was also investigated using a vibrating sample magnetometer. Further, the fabricated thin films were employed as liquefied petroleum gas (LPG) and CO 2 gas sensors. Films show better sensing behavior towards LPG in comparison to CO 2. Thus this study not only explored the influence of different compositions of Zn x Cu 1 À x Fe 2 O 4 nanocomposites on their surface morphologies, crystallite sizes, porosities, specific surface areas, UV-visible absorptions and magnetic properties, but also the influence of different in situ compositions on their sensing behaviors.

Research paper thumbnail of Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013

Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from th... more Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as "pau branco". Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The (13)C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d,p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.

Research paper thumbnail of Quantum chemical studies of structural, vibrational, NBO and hyperpolarizability of ondansetron hydrochloride

Journal of Molecular Structure, 2014

ABSTRACT In this communication, the geometry optimization, molecular electrostatic potential surf... more ABSTRACT In this communication, the geometry optimization, molecular electrostatic potential surface, wavenumber and intensity of the vibrational bands of all the possible modes of dihydrated ondansetron hydrochloride have been calculated using ab initio Hartree–Fock (HF) and density functional theory (DFT) employing B3LYP functional with 6-311++G(d,p) basis set. We have compared the calculated IR and Raman wavenumbers with the observed data. Mulliken atomic charges, HOMO–LUMO gap (ΔE), ionization potential, dipole moments and total energy have also been obtained for the optimized geometry of the molecule. UV–vis spectrum has been recorded in ethanol solvent. The TD-DFT method is used to calculate the electronic absorption parameters in gas phase as well as in solvent environment using IEF-PCM model employing 6-31G basis set. The nonlinear optical properties have been calculated. Natural bond orbital (NBO) analysis, which deals about the intra- and intermolecular charge delocalization between the bonds of a molecular system, has been done. Variation of the different thermodynamic properties with temperature has also been reported.

Research paper thumbnail of Measurement of natural background radiation level in Darchula district, Nepal

Natural background radiation level within Darchula district of Nepal was measured using a simple ... more Natural background radiation level within Darchula district of Nepal was measured using a simple portable Geiger-Müller counter. Data were collected along six different directions at different places (three-five places) of the sample sites of the district and was averaged. The average data value with their standard deviation was used for analysis. In this study, the maximum radiation counts of 51.16 2.30 CPM were reported at Satan and the minimum counts of 25.96 2.30 CPM at Gokuleshwar. The observed radiation level of the Darchula district shows that the district is below the radiation risk level (nearly 100 CPM).

Research paper thumbnail of Simulated spectra (IR and Raman), NLO, AIM and molecular docking of carisoprodol from DFT approach

BIBECHANA, 2021

The aim of this study to explore the spectroscopic behavior of carisoprodol in terms of simulated... more The aim of this study to explore the spectroscopic behavior of carisoprodol in terms of simulated spectra (IR and Raman).. The intramolecular H-bond of the molecule has been inspected from the Atoms in Molecule (AIM) approach which infers that there exist partial covalent H-bond in nature. The protein-ligand binding activity of the drug molecule has been analyzed theoretically from the molecular docking approach with the predicted targets in terms of binding energy and conventional H-bond with residue. The molecular docking analysis of the title molecule explores that the binding energy with the protein acetylcholinesterase is more than the protein epoxide hydrolase1. The nonlinear optical (NLO) behavior of title molecule has been scrutinized which motivates that the potent use of the molecule as NLO material. BIBECHANA 18 (2021) 48-57

Research paper thumbnail of Comparison of the Background Radiation Level within Kanchanpur District, Nepal

Journal of Nepal Physical Society, 2020

We have reported the background radiation of urban and some other rural places of Kanchanpur dist... more We have reported the background radiation of urban and some other rural places of Kanchanpur district, Nepal. A simple portable Geiger Muller counter was used to quantify the level of overall background radiation by collecting data of different forty seven (including six urban and forty one rural places) places within the district. Our study reveals that the background radiation level of the study district is below the risk level. The maximum background count values 33.00±4.47 (Mahakali Zonal Hospital), 33.93 ± 1.16 (Mahakali School, Mahakali -01) and 31.30±3.97 CPM (Gha gaon) have been reported which is below the risk level. The observed values of radiation counts at all the sample places indicate that Kanchanpur district is radiation risk free.

Research paper thumbnail of A Theoretical Study on Charge Transfer and Hyperpolarizability of (S)-2-amino-3-(3,4-dihydroxyphenyl)-2-methyl-propanoic Acid

Journal of Nepali Physical Society, Dec 13, 2022

The DFT approach was used to investigate the antihypertensive molecule (S)-2-amino-3-(3,4-dihydro... more The DFT approach was used to investigate the antihypertensive molecule (S)-2-amino-3-(3,4-dihydroxyphenyl)-2methyl-propanoic acid at the B3LYP/6-311++G(d,p) level of theory. The electron-hole analysis of three excited states has been performed, in which the maximum charge transfer length (2.727Å) has been calculated for the first excited state and the minimum for the third excited state (1.626 Å). On the other hand, the electron-hole overlap is found to be almost negligible for the first excited state and it is found to be maximum for the second excited state. The variation of thermodynamic properties with temperature is studied. The correlation graphs are obtained between the thermodynamic quantities (heat capacity, enthalpy, entropy) and temperature with a very high value of R 2 (>0.99). The values of dipole moment, mean polarizability, anisotropy of polarizability, first hyperpolarizability and second hyperpolarizability are found to be 3.5250 Debye, 12.6980×10-24esu, 19.8162×10 −24 esu, 0.9017×10 −30 esu and-0.0412×10 −35 esu, respectively. These values are higher than the value of urea.

Research paper thumbnail of Molecular interactions and vibrational properties of ricobendazole: Insights from quantum chemical calculation and spectroscopic methods

Journal of Molecular Structure, 2021

Abstract The structural, spectroscopic (FT-IR and FT-Raman), and physicochemical properties of ri... more Abstract The structural, spectroscopic (FT-IR and FT-Raman), and physicochemical properties of ricobendazole (RBZ) has been presented with the help of combined experimental and computational approaches. A comparison between the observed and simulated spectra show good agreement with each other. The conformational analysis was performed around eight flexible bonds to predict the most stable conformers, by employing density functional theory (DFT) at B3LYP/6–311++G(d,p) level. The chemical reactivity has been demonstrated in terms of frontier molecular orbitals (HOMO-LUMO) energy gap, molecular electrostatic potential (MEP) surface, and global reactivity. The local reactivity descriptors explored an idea about the donor/acceptor/free radical reactive sites present in the molecule. Natural bond orbital (NBO) analysis was performed to study the interactions between bonding and antibonding orbitals. The intramolecular hydrogen bonding interactions were demonstrated using QTAIM theory. Binding sites against three targets such as Poly [ADP-ribose] polymerase-1, MAP kinase p38 alpha, and Adenosine A2a receptor were identified by molecular docking analysis as RBZ is believed to inhibit against them.

Research paper thumbnail of Computational evaluation on molecular stability, reactivity, and drug potential of frovatriptan from DFT and molecular docking approach

Computational and Theoretical Chemistry, 2020

Molecular stability, fundamental chemical reactive sites, global reactivity descriptors in frovat... more Molecular stability, fundamental chemical reactive sites, global reactivity descriptors in frovatriptan molecule have been investigated by using computational evaluation and molecular docking approach. The density functional theory has been employed with standard functional B3LYP/6-311++G(d,p). The possible minimum energy structure has been predicted by implementing one-dimensional potential energy surface (PES) scan. The charge delocalization for stability of the molecule with natural bond orbital (NBO) analysis and molecular electrostatic potential (MEP) surface analysis to observe the active region for further chemical reaction with surrounding species have been performed. The chemical reactivity and hardness of the molecule in terms of HOMO-LUMO energy gap (ΔE L-H) have been implemented in terms of reactivity parameters. The potential use of frovatriptan as non-linear optical (NLO) material and its thermodynamical studies have also been performed. Moreover, the molecular docking with a predicted target has been performed to check the binding interaction as well as sites of the molecule. 2. Computational details Computational evaluation of the title compound has been carried out by using the Gaussian 09 software package [10]. The optimization has been performed by employing the default settings in the Gaussian

Research paper thumbnail of A comparative computational study on molecular structure, NBO analysis, multiple interactions, chemical reactivity and first hyperpolarisability of imatinib mesylate polymorphs using DFT and QTAIM approach

Molecular Simulation, 2013

ABSTRACT Imatinib, a phenylaminopyrimidine compound is a therapeutic drug for treatment of chroni... more ABSTRACT Imatinib, a phenylaminopyrimidine compound is a therapeutic drug for treatment of chronic myelogeneous leukaemia and gastrointestinal stromal tumours. It is well known that imatinib mesylate (ImM) exists in two polymorphic forms alpha and beta. In this work, a computational study on molecular properties of ImM polymorphs is presented using density functional theory, B3LYP functional and 6-311G(d,p) as basis set. Natural bond orbital analysis is carried out to investigate the various conjugative and hyperconjugative interactions within the molecule and their second-order stabilisation energy (E-(2)). The local nucleophilic reactivity descriptors such as Fukui functions (f(k)(-)), local softness (s(k)(-)) and electrophilicity indices (omega(-)(k)) analyses are carried out to determine the reactive sites within the molecule. To determine strength and nature of intra-and intermolecular interactions, topological parameters as electron density (ED) (rho(BCP)), Laplacian of ED (del(2) rho(BCP)) and total electron energy density (H-BCP) at bond critical points have been analysed by 'quantum theory of atoms in molecules' in detail. The computed first hyperpolarisability (beta(0)) for both forms of ImM molecule (10.927 and 10.354 x 10(-30) esu) suggests that the investigated molecule is an attractive object in future for non-linear optical properties. Molecular electrostatic potential surface of ImM has been mapped to predict the inhibitory activity and binding affinity with a panel of protein tyrosine kinases.

Research paper thumbnail of Molecular structure and quantum descriptors of cefradine by using vibrational spectroscopy (IR and Raman), NBO, AIM, chemical reactivity and molecular docking

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021

This study aims to investigate the structural and vibrational features of cefradine (the first-ge... more This study aims to investigate the structural and vibrational features of cefradine (the first-generation cephalosporin antibiotic) based on spectroscopic experiments and theoretical quantum chemical approach. The fundamental structural aspects of cefradine have been examined based on optimized geometry, spectroscopic behavior, intermolecular interaction, chemical reactivity, intramolecular hydrogen bonding, and molecular docking analysis. The most stable minimum energy conformer of the title molecule was identified by performing a one-dimensional potential energy surface scan along the rotational bonds at B3LYP/6-311++G (d,p) level of theory. The vibrational features of the molecule and information about the coupled modes were predicted. The chemical reactivity and stability of all the possible conformers of cefradine were estimated based on the HOMO-LUMO energy gap and NBO approach. The overall picture of accumulation of charges on individual atoms of the molecule was predicted by molecular electrostatic potential (MEP) surface map which in turn identifies the nucleophilic and electrophilic region or sites. The quantitative analysis of electrophilicity and nucleophilicity indices was done by Hirshfeld charge analysis and it was found that N8 atom is the most prominent site for nucleophilic attack while C14 atom is feasible for electrophilic attack. QTAIM study has also been performed to investigate the nature and strength of hydrogen bonding interactions. Besides, molecular docking studies were performed to examine the active binding residues of the target.

Research paper thumbnail of First principle study of chlorobenzene

Himalayan Physics, 2019

Chlorobenzene is a colourless flammable liquid used widely as a common solvent in the manufacture... more Chlorobenzene is a colourless flammable liquid used widely as a common solvent in the manufacture of other chemicals. In this communication, structural, electronic and vibrational study on chlorobenzene using Gaussian 09 program package employing B3LYP/6-31 G level of theory have been presented. The calculated IR and Raman spectra have been analyzed with the potential energy distribution. UV-Visible spectra taken in both the gaseous and solvent phase employing B3LYP/6-31G(d,p) level of theory have been given. The electronic transition between the frontiers energy levels together with their gap energy have analyzed.

Research paper thumbnail of Electronic, Thermodynamic Properties, Nonlinear Optical Responses, and Molecular Docking Studies on Cephalexin

Journal of Institute of Science and Technology

The topology analysis of electron localization function (ELF), localized orbital locator (LOL), t... more The topology analysis of electron localization function (ELF), localized orbital locator (LOL), the study of nonlinear optical properties, thermal properties, and biological activities of cephalexin have been performed using DFT/B3LYP and employing 6-311++G(d,p) basis sets. The Mulliken atomic charge on atoms has been calculated. The quantities describing nonlinear optical (NLO) properties like molecular polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) were comparable to the values of urea. The computed value of the second hyperpolarizability was found to be negative, which is an important feature for the system of controllable NLO devices. The thermodynamic properties like heat capacity (S), enthalpy (H), and entropy (S) are positively correlated with the temperature. Further, the title molecule shows good potentiality for binding with the selected target protein matrix metalloproteinase-2.

Research paper thumbnail of Quantum Chemical Calculation and DFT Study of Sitagliptin: Insight from Computational Evaluation and Docking Approach

Journal of Nepal Physical Society, 2020

This study aims to explore the structural and chemical behavior of sitagliptin using density func... more This study aims to explore the structural and chemical behavior of sitagliptin using density functional theory (DFT). The chemical reactivity has been studied in terms of MEP, HOMO-LUMO energy gap, Hirshfeld charge, and global and local reactivity descriptors. Thermodynamic parameters like entropy, enthalpy and specific heat capacity and, nonlinear optical (NLO) properties have been analysed. Higher value of the first hyperpolarizability than that of urea show its potential use as NLO material. Intra-molecular Hydrogen bonding and topological parameters at the bond critical point (BCP) of title molecule have been studied by using the quantum theory of atoms in molecules (QTAIM) approach. The bond of 2.3777 Å between H42…N11 is noticed to be strongest one. The pharmacological behavior and protein-ligand interaction of the title molecule have been investigated in terms of drug-likeness and molecular docking which motivates that the amine and carbonyl group bind with the amino acid of ...

Research paper thumbnail of Topological and Reactivity Descriptor of Carisoprodol from DFT and Molecular Docking Approach

Journal of Institute of Science and Technology

This study aims to investigate the optimized structure and optimized parameters of carisoprodol f... more This study aims to investigate the optimized structure and optimized parameters of carisoprodol from the DFT/B3LYP/6-31G(d,p) level of theory. The molecular electrostatic potential (MEP) map signifies that the positive potential across hydrogen of the amine group (NH2) and the negative potential around the carbonyl groups (C=O). HOMO-LUMO energy gap was found to be 8.1064 eV. The global and local reactivity parameters describe the possible chemical reactive sites in the molecule. The topological analysis of the electron localization function (ELF) and localized orbital locator (LOL) revealed that the charge localization around hydrogen atoms. The hyper-conjugative interaction between donor and acceptor orbital showed that the interaction LP(2) O4→ σ*(O2-C16) plays a vital role in the molecular stability. The molecular docking simulation encircles that the carisoprodol behaves as a good inhibitor with the target protein, Tyrosine-protein kinase ABL.

Research paper thumbnail of Measurement of natural background radiation level in Darchula district, Nepal

Scientific World

Natural background radiation level within Darchula district of Nepal was measured using a simple ... more Natural background radiation level within Darchula district of Nepal was measured using a simple portable Geiger-Müller counter. Data were collected along six different directions at different places (three-five places) of the sample sites of the district and was averaged. The average data value with their standard deviation was used for analysis. In this study, the maximum radiation counts of 51.16 2.30 CPM were reported at Satan and the minimum counts of 25.96 2.30 CPM at Gokuleshwar. The observed radiation level of the Darchula district shows that the district is below the radiation risk level (nearly 100 CPM).

Research paper thumbnail of Chemical Reactivity, Dipole Moment and First Hyperpolarizability of Aristolochic Acid I

Journal of Institute of Science and Technology, 2016

Aristolochic acids (AAs) have been used in the treatment of oedema in Chinese herb medicine since... more Aristolochic acids (AAs) have been used in the treatment of oedema in Chinese herb medicine since long ago. In this paper, molecular electrostatic potential, chemical reactivity and non linear optical properties of aristolochic acid I (AA I) have been analyzed using density functional theory employing 6-311++G(d,p) basis set. The chemical reactivity of the molecule has been explained with the help of chemical reactivity descriptors, molar refractivity and the molecular electrostatic potential surface (ESP). The calculated dipole moment and first order hyperpolarizability show that the molecule possesses non-linear optical property.

Research paper thumbnail of A combined experimental (IR, Raman and UV-Vis) and quantum chemical study of canadine

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 4, 2017

Plant based natural products cover a major sector of the medicinal field, as such focus on plant ... more Plant based natural products cover a major sector of the medicinal field, as such focus on plant research has been increased all over the world. As an attempt to aid that research, we have performed structural and spectroscopic analysis of a natural product, an alkaloid: canadine. Both ab initio Hartree-Fock (HF) and density functional theory (DFT) employing B3LYP using 6-311++G(d,p) basis set were used for the calculations. The calculated vibrational frequencies were scaled and compared with the experimental infrared and Raman spectra. The complete vibrational assignments were made using potential energy distribution. The structure-activity relation has also been interpreted by mapping electrostatic potential surface and evaluating the reactivity descriptors, which are valuable information for quality control of medicines and drug-receptor interactions. Natural bond orbital analysis has also been performed to understand the stability and hyperconjugative interactions of the molecul...

Research paper thumbnail of Conformational, Chemical Reactivity, Thermodymanic Properties and the Sem Study of Yohimbine Hydrochloride

We have presented a study on structural conformation of yohimbine hydrochloride using density fun... more We have presented a study on structural conformation of yohimbine hydrochloride using density functional theory (DFT) method. A short description about the surface morphology with scanning electron microscopy imaging has been included. Correlation between different thermodynamic properties with variation in the temperature has been given. The global and local chemical reactivity descriptors have been calculated, from which nucleophilicity and electrophilicity of the given atomic sites in the molecule can be known.

Research paper thumbnail of Structure, MESP and HOMO-LUMO study of 10-Acetyl- 10H-phenothiazine 5-oxide using vibrational spectroscopy and quantum chemical methods

BIBECHANA, 2012

In this communication, we have presented the geometry optimization, complete vibrational study wi... more In this communication, we have presented the geometry optimization, complete vibrational study with potential energy distribution (PED) and frontier orbital energy gap for the 10-Acetyl-10H-phenothiazine 5-oxide (APTZ) molecule using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method employing 6-311++G(d,p) basis set. The calculated IR and Raman spectra with their intensities, molecular electrostatic potential (MESP) surface and highest occupied molecular orbital (HOMO) - lowest unoccupied molecular orbital (LUMO) plot have been given. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7151 BIBECHANA 9 (2013) 38-49

Research paper thumbnail of Synthesis, characterization, magnetic properties and gas sensing applications of ZnxCu1−xFe2O4 (0.0≤x≤0.8) nanocomposites

Materials Science in Semiconductor Processing, 2014

In the present work Zn x Cu 1 À x Fe 2 O 4 nanocomposites were synthesized with a wide compositio... more In the present work Zn x Cu 1 À x Fe 2 O 4 nanocomposites were synthesized with a wide composition range (0.0 rx r0.8 in the steps of x ¼ 0.2) using a sol-gel method and thin films were fabricated using a spin-coating process. The synthesized materials were analyzed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, differential scanning calorimetry, UV-visible absorption and infrared spectroscopic techniques for their appropriate characterization. The XRD revealed the cubic spinel structure for each composition and the minimum crystallite size was found to be 10.4 nm. In order to study the thermodynamics during the synthesis, pre-and post-annealed materials were analyzed. An influence of the zinc on the magnetic properties was also investigated using a vibrating sample magnetometer. Further, the fabricated thin films were employed as liquefied petroleum gas (LPG) and CO 2 gas sensors. Films show better sensing behavior towards LPG in comparison to CO 2. Thus this study not only explored the influence of different compositions of Zn x Cu 1 À x Fe 2 O 4 nanocomposites on their surface morphologies, crystallite sizes, porosities, specific surface areas, UV-visible absorptions and magnetic properties, but also the influence of different in situ compositions on their sensing behaviors.

Research paper thumbnail of Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013

Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from th... more Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as "pau branco". Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d,p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The (13)C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d,p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.

Research paper thumbnail of Quantum chemical studies of structural, vibrational, NBO and hyperpolarizability of ondansetron hydrochloride

Journal of Molecular Structure, 2014

ABSTRACT In this communication, the geometry optimization, molecular electrostatic potential surf... more ABSTRACT In this communication, the geometry optimization, molecular electrostatic potential surface, wavenumber and intensity of the vibrational bands of all the possible modes of dihydrated ondansetron hydrochloride have been calculated using ab initio Hartree–Fock (HF) and density functional theory (DFT) employing B3LYP functional with 6-311++G(d,p) basis set. We have compared the calculated IR and Raman wavenumbers with the observed data. Mulliken atomic charges, HOMO–LUMO gap (ΔE), ionization potential, dipole moments and total energy have also been obtained for the optimized geometry of the molecule. UV–vis spectrum has been recorded in ethanol solvent. The TD-DFT method is used to calculate the electronic absorption parameters in gas phase as well as in solvent environment using IEF-PCM model employing 6-31G basis set. The nonlinear optical properties have been calculated. Natural bond orbital (NBO) analysis, which deals about the intra- and intermolecular charge delocalization between the bonds of a molecular system, has been done. Variation of the different thermodynamic properties with temperature has also been reported.

Research paper thumbnail of Measurement of natural background radiation level in Darchula district, Nepal

Natural background radiation level within Darchula district of Nepal was measured using a simple ... more Natural background radiation level within Darchula district of Nepal was measured using a simple portable Geiger-Müller counter. Data were collected along six different directions at different places (three-five places) of the sample sites of the district and was averaged. The average data value with their standard deviation was used for analysis. In this study, the maximum radiation counts of 51.16 2.30 CPM were reported at Satan and the minimum counts of 25.96 2.30 CPM at Gokuleshwar. The observed radiation level of the Darchula district shows that the district is below the radiation risk level (nearly 100 CPM).

Research paper thumbnail of Simulated spectra (IR and Raman), NLO, AIM and molecular docking of carisoprodol from DFT approach

BIBECHANA, 2021

The aim of this study to explore the spectroscopic behavior of carisoprodol in terms of simulated... more The aim of this study to explore the spectroscopic behavior of carisoprodol in terms of simulated spectra (IR and Raman).. The intramolecular H-bond of the molecule has been inspected from the Atoms in Molecule (AIM) approach which infers that there exist partial covalent H-bond in nature. The protein-ligand binding activity of the drug molecule has been analyzed theoretically from the molecular docking approach with the predicted targets in terms of binding energy and conventional H-bond with residue. The molecular docking analysis of the title molecule explores that the binding energy with the protein acetylcholinesterase is more than the protein epoxide hydrolase1. The nonlinear optical (NLO) behavior of title molecule has been scrutinized which motivates that the potent use of the molecule as NLO material. BIBECHANA 18 (2021) 48-57

Research paper thumbnail of Comparison of the Background Radiation Level within Kanchanpur District, Nepal

Journal of Nepal Physical Society, 2020

We have reported the background radiation of urban and some other rural places of Kanchanpur dist... more We have reported the background radiation of urban and some other rural places of Kanchanpur district, Nepal. A simple portable Geiger Muller counter was used to quantify the level of overall background radiation by collecting data of different forty seven (including six urban and forty one rural places) places within the district. Our study reveals that the background radiation level of the study district is below the risk level. The maximum background count values 33.00±4.47 (Mahakali Zonal Hospital), 33.93 ± 1.16 (Mahakali School, Mahakali -01) and 31.30±3.97 CPM (Gha gaon) have been reported which is below the risk level. The observed values of radiation counts at all the sample places indicate that Kanchanpur district is radiation risk free.