Electrostatic Potential Contour Research Articles

A Detailed Study of Solvent-Ligand Interactions and in Silico Biological Activity Predictions on Hydroxychloroquine

In this study, the effects of solvent environment changes, which are of critical importance in drug production processes, on the geometric structure and physicochemical parameters of the Hydroxychloroquine (HQC) molecule were investigated. For this purpose, optimized molecule structures were obtained using Density Functional Theory in vacuum and solvent environments. Based on the optimized structures, the molecule's thermochemical properties, atomic charges, and chemical reactivity data were calculated in vacuum and solvent environments. Moreover, the molecule's molecular electrostatic potential map and HOMO-LUMO contour maps were drawn. Vibrational frequencies, intensities, and assignments in solvent environments were determined. The characteristics of the hydrogen bonding interactions established between solvent molecules and HQC were determined in detail. ADME, toxicity, and drug-likeness predictions of the molecule were made. The study results showed that while the structural, chemical, and physical properties of the HQC molecule were severely affected when transferred to the solvent environment, they were less affected by the changes between solvent environments. In addition, very strong h-bond interactions are established between the solvent molecules and HQC.

A systematic study on interplay between intermolecular hydrogen bonding and aromaticity

In this study, the interplay between aromaticity and intermolecular hydrogen bonding was investigated in some heterocyclic compounds using quantum mechanical calculations. The NH … O intermolecular hydrogen bonds between formamide and NH and CO functional groups of the selected compounds enhance the delocalisation of the six-membered ring electron cloud, resulting in an increase in the aromaticity of the ring. The contribution of various factors to the binding energy, including the stabilisation energy of the interplay between aromaticity and H-bonding, was estimated using two model systems. The relative binding energies and the estimated stabilisation energies of the aforementioned interplay can be explained by the weights of resonance structures calculated using the natural resonance theory (NRT) analysis with the natural bond orbitals (NBO) method. These weights reflect the tendency of ring nitrogen lone pairs to contribute to the π electron cloud of the ring. The results of the topological analysis of electron charge densities using the atoms in molecules (AIM) method were used to estimate the aromaticity of the ring. Aromaticity indices, particularly nucleus-independent chemical shifts (NICS) calculated one angstrom above the ring plane, are in good linear correlation with the estimated stabilisation energies and electron density at the H-bond critical points. The sum of the total nuclear spin–spin coupling 1J of adjacent atoms of the ring (Σ1J), and the J values of H-bond donor and H-bond acceptor atoms, 1HJNO, which are in good agreement with the energy data and aromaticity indices, can be used as measures of the interplay between aromaticity and H-bonding. The interplay between H-bonding and the aromaticity of the ring is clearly evident from the changes in the pattern of the molecular electrostatic potential (MEP) contour maps at 1.7 Å above the plane of the molecule upon H-bond complexation.

A Biophysical Study of Ru(II) Polypyridyl Complex, Properties and its Interaction with DNA.

Mononuclear Ru(II)Polypyridyl complexes of type [Ru(A)2BPIIP] (ClO4)2.2H2O, where BPIIP = 2-(3-(4-bromophenyl)isoxazole-5-yl)-1 H-imidazo [4,5-f] [1, 10]phenanthroline and A = bpy = bipyridyl (1), phen = 1,10 Phenanthroline (2), dmb = 4, 4' -dimethyl 2, 2'- bipyridine (3) & dmp = 4,4'-dimethyl-1,10 -Ortho Phenanthroline (4), were synthesized and their antibacterial activity were examined. The synthesized complexes were characterized and their interaction with DNA was studied using Computational and Biophysical methods (Absorption, emission methods, and viscosity). Molecular modelling studies were carried out for molecular geometry and electronic properties (Frontier molecular orbital HOMO-LUMO). The electrostatic potential surface contours for the complexes were analysed to give their nucleophilic level of sensitivity.The study reveals that the Ru(II) Polypyridyl complexes bind to DNA preponderantly by intercalation. The results recommend that the phen and dmp complex have more effective binding ability than the bpy and dmb, indicating the role of the ancillary ligand in determining their specificity for DNA binding. Further molecular docking studies suggested an octahedral geometry and bind to DNA by preferential binding to Guanine. The docking study additionally sustains the binding constant data acquired with the absorption and emission techniques.The results reveal that the nature of the ancillary Ligand plays a considerable role for the intercalation of the Ru(II) polypyridyl complex to DNA, which subsequently influences the antibacterial activity. Biological studies conducted on Gram-Negative (E.coli and K.pneumonia) and Gram-Positive (S. aureus and E. faecalis) bacteria establish that complex 1 and 2 were considerably active against S. aureus and E. coli.

Comparative study on adsorption behaviour of the monolayer graphene, boron nitride and silicon carbide hetero-sheets towards carbon monoxide: Insights from first-principle studies

A comprehensive study on the sensitivity of graphene, boron nitride, silicon carbide and their in-plane hetero-sheets towards carbon monoxide (CO) was performed using first-principle density functional theory calculations. To rationalize the CO adsorption on pristine and hetero-sheets, molecular electrostatic potential contours, HOMO-LUMO distributions, the density of states plots, atomic charge distributions and quantum chemical descriptors were calculated. The optimized geometries showed that the CO molecule oriented itself at different angles with respect to sheets. A shift in the characteristic vibrational frequency of CO was observed through theoretically computed infra-red spectra. The maximum shift was observed for the GRA/SiC hetero-sheet. Charge analysis showed the partial charge transfer from the CO molecule to the adsorbent sheets. This was further confirmed by the HOMO-LUMO distributions of the interacting species. The reactivity descriptors calculated based on the HOMO-LUMO energies, molecular electrostatic potential contours and DOS plots showed that GRA/SiC hetero-structure exhibited better sensitivity towards CO than other sheets. The calculated adsorption energies, corrected for basis set superposition error, ranged from −3 to −10 kJ mol−1, confirming the physical nature of adsorption.

Adsorption behaviour of boron nitride nanosheets towards the positive, negative and the neutral antibiotics: Insights from first principle studies

In this study, the adsorption of ampicillin (APC, positive), ciprofloxacin (CFX, neutral) and cephalosporin (CLS, negative) antibiotics on boron nitride nanosheets (BNNS) were investigated using the first principle density functional theory. To make a comprehensive study on the adsorption of the positive, negative and neutral antibiotics on the BNNS, investigations were made using the electrostatic potential maps, natural-bonding orbitals charge distributions and the density of states plots. Theoretical IR spectra of clusters before and after adsorption were obtained to study the stability of the post adsorption complexes. Koopman's approach was used to study the properties of antibiotics and complex clusters. The quantum mechanical descriptors of various systems were also calculated to comment upon the feasibility of the interactions. From the electrostatic potential contours and the natural-bonding orbitals charge transfer data, it was clear that the maximum charge accretion occurred in the CLS-BNNS complex. APC was the closest to the BNNS at a distance of 2.52 Å. The adsorption energies calculated for the three complex clusters revealed that CLS released the most adsorption energy of −167.74 kJ/mol, indicating that interaction was maximum for CLS antibiotics. CLS-BNNS cluster exhibited the smallest HOMO-LUMO gap, indicating that CLS antibiotic adsorption on the BNNS was more favourable among the three antibiotics. The plausible mechanism investigated indicated that the interactions between antibiotics and BNNS were mainly due to the weak Van der Waal forces. This theoretical study showed the promising application of BNNS as an effective adsorbing material for removing negatively charged antibiotics from an aqueous stream.

Quantum Chemical Calculations of 2-Methoxy-4-[(3-p-Methylbenzyl-4,5-Dihydro-1H-1,2,4-Trıazol-5-One-4-YL)Azomethine] Phenyl-2-Methylbenzoate Molecule

2-Methoxy-4-[(3-p-methylbenzyl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl) azomethine] phenyl-2-methylbenzoate was optimized by using Density Functional Theory (DFT/B3LYP, B3PW91) methods (Frisch et al., 2009; Wolinski et. al., 1990). 1H-NMR and 13C-NMR isotropic shift values were calculated by the method of GIAO using the program package Gaussian G09 (Wolinski et al., 1990). Theoretical and experimental values were inserted into the grafic according to equatation of δ exp=a+b. δ calc. Experimental data obtained from the literature (Yüksek et al., 2018). The standard error values were found via SigmaPlot program with regression coefficient of a and b constants. Furthermore, the veda4f program was used in defining of IR data theoretically (Jamróz, 2004). Theoretically calculated IR data are multiplied with appropriate adjustment factors (Merrick et al., 2007) and the data obtained according to DFT(B3LYP, B3PW91) method are formed using theoretical infrared spectrum. Also, dipole moments, the HOMO-LUMO energy, ΔEg, total energy of the molecule, bond lengths and Mulliken charges, the molecular surfaces such as molecular electrostatic potential (MEP) and MEP contour maps, the total density, the electron density and the electrostatic potential were calculated with same method and functions.

Evaluation of the Method of Binding Tamoxifen to DNA Experimentally and Computationally

Background and Aim: Tamoxifen is a group of drugs of selective estrogen receptor modulators, and is one of the drugs effective in the prevention and treatment of some cancers (such as breast cancer). In this study, the interaction of tamoxifen with DNA is investigated experimentally. Also, the electronic structure (at atomic scale) of the molecular system of tamoxifen was theoretically investigated, using atom in molecule (AIM) theory. Methods & Materials: First, in the experimental section of this study, the interaction of Tamoxifen with DNA were investigated by UV-ViS technique and hydrodynamic method (Viscometry). In addition, the analysis of the experimental results shows the obvious effect of concentration on the mechanism of how the tamoxifen molecule binds to DNA. Then, in the theoretical part of this research, using computational biophysical chemistry methods, some properties of tamoxifen molecular system, such as electronic Density of States (DOS), boundary orbital’s energy (HOMO/LUMO), Electrostatic Potential Energy (EPS) and electronic contour maps of the electron density and its Laplacian, will be calculated. Ethical Considerations: This article is a meta-analysis with animal sample. Results: Result of the UV-ViS spectroscopy technique and viscometry indicated hyperchromism and hypochromism effect. In addition, the result were depend on the concentration of the drug and affected the kind of binding of Tamoxifen to DNA. the analysis of computational studies on the drug tamoxifen suggests that the mechanism of the local charge/energy distribution in the molecular system of tamoxifen plays an important role in how this drug binds to DNA. Conclusion: Based on the experimental results of UV-ViS technique and viscometry, as well as the electronic/vibrational properties of the tamoxifen molecular system, it was defined that the Tamoxifen interacts significantly with all the binding sites of DNA.

Quantum chemical, spectroscopic investigations, molecular docking and cytotoxic evaluation of 1-Methyl-indole-3-carboxaldehyde

Abstract 1-Methyl-indole-3-carboxaldehyde (MEICA) molecule was characterized experimentally using spectroscopic techniques like FT-IR, FT-Raman and UV-Vis. The optimized molecular structure, vibrational and electronic properties of the title compound were calculated by using density functional theory (DFT) method and compared with the experimental results. The color map and contour map obtained from electron Localization Function (ELF) and Local Orbital Localizer (LOL) helps to investigate the electron delocalization in the molecule. The experimental and theoretical wavenumbers of the title molecule were assigned on the basis of potential energy distribution (PED) using VEDA 4.0 program. The charge delocalization and hyper conjugative interactions of the MEICA molecule were investigated using natural bond orbital (NBO) analysis. The HOMO-LUMO energy gap and related molecular properties were calculated. The electronic transitions were performed by TD-DFT calculations and validated experimentally. The Molecular electrostatic potential (MEP) contour maps and Fukui function analysis were performed to visualize the charge distribution in the molecule. The molecular docking analysis reveals that the MEICA ligand shows better inhibitory activity against CK2 which causes lung cancer. The cytotoxic study was performed against human lung cancer cell lines (A549) with IC50 value of 168 μg mL−1. Hence, the MEICA molecule can be used as a drug for the treatment of lung cancer.

Effects of Nitridation and Vinylation of Imidazolium Rings on Hydrogen Bonding Interactions, π-π-Stacking Structures, and Dynamical Heterogeneities in Imidazolium and Triazolium Ionic Liquids.

Extensive atomistic simulations have been performed to investigate how nitridation and vinylation of cations affect hydrogen bonding structures and dynamics, π-π-stacking interactions between cation-ring planes, and translational and rotational dynamics of ion species in ionic liquids (ILs) consisting of bis(trifluoromethylsulfonyl)imide anions coupled with either imidazolium or triazolium cations. Both nitridation and vinylation of cations have remarkable effects on molecular electrostatic potential contours of cations and polarities of cation-ring hydrogen atoms, leading to distinct structures and dynamics in their hydrogen bonding associations with representative atoms in anions and in triazolium cations. Both imidazolium- and triazolium-ring planes exhibit varied π-π-stacking structures depending on nitridation positions on imidazolium rings. The vinyl-substituted cations have more prominent π-π-stacking interactions than their methyl-based counterparts because of the formation of π-conjugated ring vinyl moieties. Polar and apolar groups in ion species exhibit remarkable translational and rotational dynamics and distinct diffusion distributions in IL matrices at different timescales. The nitridation and vinylation of cations lead to enhanced deviation of translational mobilities of ion species from Gaussian behavior, and cations have a higher degree of dynamical heterogeneity than their coupled anions.

Improved Performance of Stair-Stepping Buffer-Gate 4H Silicon Carbide Metal Semiconductor Field Effect Transistor

The 4H SiliconCarbide metal semiconductor field effect transistor (4H-SiC MESFET) with a buffer layer between the gate and channel (BG) is optimized and a new stair-stepping buffer-gate structure (SBG) is proposed for improving the breakdown characteristics. The terminal technology of breakdown point transfer (BPT) is applied in 4H-SiC SBG-MESFET in order to scatter the electric field lines and transfer the breakdown point. The breakdown mechanism is further investigated by simulating the surface electric field distribution and electrostatic potential contours. The results show that the breakdown voltage is increased from 120 V to 180 V, improved by the rate of 50% while the current density has hardly deteriorated, and thus the current density is improved from 9.35 W/mm to 13.2 W/mm in comparison with BG structure.

How Molecular Chiralities of Bis(mandelato)borate Anions Affect Their Binding Structures With Alkali Metal Ions and Microstructural Properties in Tetraalkylphosphonium Ionic Liquids.

Spiroborate anion-based inorganic electrolytes and ionic liquids (ILs) have fascinating electrochemical and tribological properties and have received widespread attention in industrial applications. The molecular chiralities of spiroborate anions have a significant effect on the microstructures and macroscopic functionalities of these ionic materials in application and thus deserve fundamental consideration. In the current work, we performed quantum chemistry calculations to address the binding strength and coordination structures of chiral bis(mandelato)borate ([BMB]) anions with representative alkali metal ions, as well as the electronic properties of alkali metal ion-[BMB] ion pair complexes. The optimized [BMB] conformers are categorized into V-shaped, bent, and twisted structures with varied electrostatic potential contours and conformational energies and distinct alkali metal ion-[BMB] binding structures. Alkali metal ions have additional associations with phenyl groups in V-shaped [BMB] conformers owing to preferential cation-π interactions. Furthermore, the effects of the molecular chiralities of [BMB] anions on the thermodynamics and microstructural properties of tetraalkylphosphonium [BMB] ILs were studied by performing extensive atomistic interactions. Oxygen atoms in [BMB] anions have competitive hydrogen bonding interactions with hydrogen atoms in cations depending on the molecular chiralities and steric hindrance effects of [BMB] anions. However, the molecular chiralities of [BMB] anions have a negligible effect on the liquid densities of tetraalkylphosphonium [BMB] ILs and the spatial distributions of boron atoms in anions around phosphorous atoms in cations. Enlarging tetraalkylphosphonium cation sizes leads to enhanced cation-anion intermolecular hydrogen bonding and Coulombic interactions due to enhanced segregation of polar groups in apolar networks in heterogeneous IL matrices, as verified by scattering structural functions.

Synthesis, Density Functional Theory Band Structure Calculations, Optical, and Photoelectrical Characterizations of the Novel (9‐Bromo‐3‐cyano‐5‐oxo‐1,5‐dihydro‐2H‐chromeno[4,3‐b]pyridin‐2‐ylidene)propanedinitrile

Ring transformation of 6‐bromochromone‐3‐carbonitrile (1) with malononitrile dimer in basic medium furnished the unexpected (9‐bromo‐3‐cyano‐5‐oxo‐1,5‐dihydro‐2H‐chromeno[4,3‐b]pyridin‐2‐ylidene)propanedinitrile (2, BCOCPP). Density functional theory, theoretical investigation of the electronic structure, geometries linear polarizability ⟨Δα⟩ (Quadrupole moment), first‐order hyperpolarizability ⟨β⟩ (Octapole moment), natural bonding orbital, molecular electrostatic potential contours, thermo‐chemical parameters, harmonic vibration frequencies, the FT‐IR spectrum of the compound (2, BCOCPP) in the solid phase was recorded, and time‐dependent density functional theory calculations at the B3LYP/6‐311G (d,p) level of theory, UV‐Vis spectra, in both ethanol and dioxane solvents have been employed for compound (2, BCOCPP). The geometrical and energetic parameters have been extensively investigated to reveal the reason behind the selective formation of compound (2, BCOCPP), instead of expected product 3. The Coulomb‐attenuating method‐B3LYP and Corrected Linear Response Polarizable Continuum Model studied for theoretically obtaining the electronic absorption spectra in gas phase, ethanol, and dioxane, respectively, and indicate a good agreement with the observed spectra. The heterojunction based on BCOCPP showed phototransient properties under various illumination intensities that give the recommendation of the studied heterojunction in the field of optoelectronic device application.

Quantum chemical analysis on supramolecular assemblies of guanidinium tetrafluoroborate (GFB) crystal structure: Emission and NLO behavior

The present work explains the experimental and theoretical aspects of guanidinium tetrafluoroborate (GFB) single crystal. The solubility nature of the GFB single crystal was analyzed. The surface of the grown crystal was examined through chemical etching study. Emission properties were characterized using photoluminescence study. CIE colour chromaticity coordinates afford the dominant color emission of the title compound. The optical limiting property of the titular compound was ascertained using z-scan technique. The solid state parameters, such as Plasma energy, Penn gap energy, Fermi energy and electronic polarizabilty were calculated. The intermolecular interactions in the title molecule were studied using Hirshfeld surface analysis. A detailed quantum chemical calculation of the title crystal was performed. Mulliken atomic charge analysis revealed the charge distribution in the molecule. The molecular electrostatic potential (MEP) contour maps were used to study the interactions of guanidinium with fluoroborate ions in the crystal. The charge transfer mechanism was analysed using computed HOMO-LUMO orbitals. The 3D-matrix of hyperpolarizability tensor components was computed to enumerate the NLO activity. The various thermodynamic properties of the GFB molecule were computed. The electronic exchange interaction in the title compound was determined by natural bond orbital (NBO) analysis.

DFT and TD-DFT calculations of metallotetraphenylporphyrin and metallotetraphenylporphyrin fullerene complexes as potential dye sensitizers for solar cells

Density functional theory (DFT) and time-dependent DFT calculations have been employed to model metallotetraphenylporphyrin dyes and metallotetraphenylporphyrin –fullerene complexes in order to investigate the geometries, electronic structures, the density of states, non-linear optical properties (NLO), IR–vis spectra, molecular electrostatic potential contours, and electrophilicity. To calculate the excited states of the tetraphenyl porphyrin analogs, time-dependent density functional theory (TD-DFT) are used. Their UV–vis spectra were also obtained and a comparison with available experimental and theoretical results is included. The results reveal that the metal and the tertiary butyl groups of the dyes are electron donors, and the tetraphenylporphyrin rings are electron acceptors. The HOMOs of the dyes fall within the (TiO2)60 and Ti38O76 band gaps and support the issue of typical interfacial electron transfer reaction. The resulting potential drop of Mn-TPP-C60 increased by ca. 3.50% under the effect of the tertiary butyl groups. The increase in the potential drop indicates that the tertiary butyl complexes could be a better choice for the strong operation of the molecular rectifiers. The introduction of metal atom and tertiary butyl groups to the tetraphenyl porphyrin moiety leads to a stronger response to the external electric field and induces higher photo-to-current conversion efficiency. This also shifts the absorption in the dyes and makes them potential candidates for harvesting light in the entire visible and near IR region for photovoltaic applications.

Vibrational investigation on pharmaceutical activity of m-xylene-4-sulphonic acid by quantum computational and experimental support

ABSTRACTDetailed physical, chemical, thermal and circular vibrational investigations have been made on FT-IR, FT-Raman, NMR and UV–Visible spectra of m-xylene-4-sulphonic acid. The modification of the basic property of the base compound favoured by the asymmetric orientation of the charge levels among the atoms of the compound has been discussed in detail. The transitional pattern among the natural bond orbitals emphasized the inducement of the antibacterial and antifungal activity in the compound. Strong interpretations of the physical and chemical properties by intense observation using excitations between the electronic energy levels within the molecule have been carried out. The arrangement of the dipole moment of the bonds and the change of the resultant magnetic moment were observed from the average polarizability first-order diagonal hyperpolarizability. The receptor and inhibition property of the molecule were interpreted by the identification of reactive sites from the molecular electrostatic potential contour map. The chemical reaction continuity is keenly observed from thermodynamic analysis.

Theoretical Study and Experimental Analysis on 2-(1-Ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetic Acid (3) Using the DFT Approach

Riley oxidation of 3-acetyl-4-hydroxyquinolin-2(1H)-one (1) with selenium dioxide furnished the unexpected product 2-(1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetic acid (3). The expected product 2-(1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)-2-oxoacetaldehyde (2) was excluded based on the spectral data. The elemental analysis and spectral data (IR, and 1H NMR) was used to deduce the structure of compound 3. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations of the electronic structure at the B3LYP/6-311G (d,p) level of theory have been employed for compound 3 to investigated its geometry, linear polarizability 〈Δα〉, first-order hyperpolarizability 〈β〉, natural bonding orbital (NBO), molecular electrostatic potential contours (MEP and ESP), electrophilicity, and UV–Vis spectra in both ethanol and dioxane solvents. The geometrical and energetic parameters have been extensively investigated to reveal the reason behind the selective formation of compound 3, rather than the expected product 2. FT-IR spectra in the solid phase were recorded for compound 3. The thermo-chemical parameters, harmonic vibration frequencies, and the equilibrium geometries have been calculated at the DFT/B3LYP/6-311G (d,p) level. Time-dependent density functional theory (TD-DFT) was used to calculate the excited states of compound 3. Changes in the solvent cause changes in the band intensities and in the positions of the band maxima (λmax). The excited state was identified and contributes to the electronic configurations, and it was characterized in terms of the relevant MOs. The theoretical spectra were computed using the Coulomb-attenuating method (CAM-B3LYP), using the basis set 6-311G (d,p) in the gas phase, and the polarizable continuum model (PCM) in dioxane and ethanol. The results indicate good agreement with the observed spectra.

Vibrational and NMR Investigation on Pharmaceutical Activity of 2,5- Dimethoxy-4-Ethylamphetamine by Theoretical and Experimental Support

The Detailed physical, chemical, thermal and circular vibrational investigations have been made on FT-IR, FTRaman, NMR and UV-Visible spectra of 2,5-Dimethoxy-4-ethylamphetamine. The modification of the basic property (deficit hyperactivity disorder) of the base compound (Amphetamine) is favoured by the insertion of two methoxy and ethyl-methyl groups have been discussed in detail. The transitional pattern among NBO emphasized the inducement of the psychedelic activity in the compound. The strong interpretation made on the physical and chemical properties by intense observation using excitations between the electronic energy levels within the molecule have been carried out. The arrangement of the dipole moment of the bonds and the change of resultant magnetic moment were observed from the average Polarizability first order diagonal hyperpolarizability. The receptor and inhibition property of the molecule were interpreted by the identification of reactive sites from molecular electrostatic potential contour map. The chemical reaction continuity is keenly observed from thermodynamical analysis.

Nanostructural adsorption of vanadium oxide on functionalized graphene: a DFT study.

Rutile-monoclinic phase transitions of vanadium oxide (VO2) nanocrystals adsorbed on graphene-based substrates are of current scientific interest, although their adsorption and growth mechanisms have not been investigated theoretically. In this study, we use density functional theory (DFT) calculations for determining the binding energies and predicting the corresponding directions of growth of VO2 nanostructures (rutile and M1-monoclinic) interacting with both pure graphene and functionalized graphene nanoribbons. Several adsorption sites of pure graphene including the top, bridge, and hollow sites are considered, while additional adsorption sites of functionalized graphene nanoribbons, epoxy, alcohol and carboxylate are investigated. Vanadium oxide nanostructures are found to favor physical adsorption on the hollow sites of pure graphene, while chemical adsorption is favored on the carboxylate sites of functionalized graphene nanoribbons (FGNRs). Charge density maps showed the electron distribution originating from the interaction between VO2 and graphene substrates, helping to understand the mechanism of charge transfer. Electronic local potentials showed vertical growth tendencies for rutile VO2, while M1-monoclinic VO2 showed horizontal growth tendencies. Partial density of states (PDOS) helped examine the electronic structure of metallic rutile VO2 binding to hollow and carboxylate sites of functionalized graphene. These results provide an improved understanding of the controlled and oriented growth of VO2 nanocrystals on graphene-based substrates which can enable various properties such as the metal-insulator transition (MIT) of VO2 in light regulation applications.

Conformational, vibrational spectroscopic, nonlinear optical activity, and structure–activity studies on 2-hydroxy-3,5-dinitropyridine: Combined experimental and density functional theory approach

ABSTRACTThe conformational analysis was carried out to predict the most stable, optimized structure of 2-hydroxy-3,5-dinitropyridine among various conformers. The most stable, optimized structure of the molecule was predicted by the density functional theory (DFT) using the B3LYP method with the cc-pVQZ basis set. The vibrational frequencies, natural atomic charge distribution, and thermodynamic properties were calculated. The molecular electrostatic potential surface and contour map were simulated. The experimental and theoretical vibrational frequencies were assigned on the basis of potential energy distribution calculation. The density of states (DOS) spectrum was simulated. The frontier molecular orbital analysis was carried out. The natural bond orbital (NBO) analysis was performed to evaluate the donor–acceptor interactions in the molecule. The structure–activity descriptors were determined by Fukui functions and local reactivity descriptor calculations. The nonlinear optical (NLO) activity of the molecule was studied. The second harmonic generation test confirms the NLO activity of the title molecule.

Spectroscopic investigation and chemical properties analysis on anticancer compound; α,α,ά,ά-Tetrabromo-p-Xylene with computational analysis

In order to explore the pharmaceutical applications, the vibrational spectra of α,α,ά,ά-Tetrabromo-p-Xylene (4αBX) were recorded using IR, Raman and NMR spectrometer with FT technique. The modified optimized structural bond parameters and vibrational group wavenumbers of molecule based on substitutional bonds, Mulliken atomic charge distribution, frontier molecular orbital levels, chemical properties, temperature dependence of thermodynamic parameters, NLO studies and natural bond orbital calculations of the molecule were performed using the HF and DFT model theories. The intense observation was made over the excitations between the electronic energy levels within the molecule which enable to explore the electronic properties. The distribution of Mulliken charges of present molecule were calculated and were interrelated with the architecture of the molecular bonds. The charge transformation over the frontier molecular orbitals between the ligand and rings has been thoroughly observed. The average Polarizability first order diagonal hyperpolarizability have been calculated and from which the linear and non linear optical activity of the molecule is interpreted in detail. The reactive site of the molecule was predicted from the molecular electrostatic potential contour map. From the thermodynamical analysis, it was found that, the values of thermo dynamic parameters were increasing with increasing temperature.