scholarly journals Quantum chemical studies, spectroscopic analysis and molecular structure investigation of 4-Chloro-2-[(furan-2-ylmethyl)amino]-5-sulfamoylbenzoic acid

2019 ◽  
Vol 38 (2) ◽  
pp. 253
Author(s):  
Balamurugan Natarajan
Keyword(s):  
Chemical Shifts ◽  
Population Analysis ◽  
Visible Spectrum ◽  
Basis Set ◽  
Mulliken Population ◽  
B3lyp Method ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Uv Visible ◽  
Molecular Structure Investigation

In this study, the FTIR, FT-Raman and UV-visible Spectra of furosemide molecule, C12H11ClN2O5S (with named, 4-chloro-2-[(furan-2-ylmethyl)amino]-5-sulfamoylbenzoic acid), were recorded experimentally and theoretically. The optimized geometrical structure, harmonic vibration frequencies, and chemical shifts were computed using a hybrid-DFT (B3LYP) method and 6-31G(d,p) as the basis set. The complete assignments of fundamental vibrations were performed on the basis of the experimental results and Total Energy Distribution (TED) of the vibrational modes. The first order hyperpolarizability and relative properties of furosemide were calculated. The UV-Visible spectrum of the compound was recorded in the range 200–400 nm and the electronic properties, such as HOMO and LUMO energies, were determined by Time-Dependent DFT approach. Furthermore, Mulliken population analysis and thermodynamic properties were performed using B3LYP/6-31G(d,p) level for the furosemide compound.

scholarly journals Spectroscopic (FT-IR, Raman, NMR) and DFT Quantum Chemical Studies on Phenoxyacetic Acid and Its Sodium Salt

2012 ◽  
Vol 27 ◽  
pp. 307-313 ◽  
Author(s):  
M. Samsonowicz ◽  
E. Regulska ◽  
W. Lewandowski
Keyword(s):  
Sodium Salt ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Dipole Moments ◽  
Population Analysis ◽  
Phenoxyacetic Acid ◽  
Geometrical Structures ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Ft Ir

FT-IR, Raman, and NMR spectra of phenoxyacetic acid and its sodium salt were recorded and analyzed. Optimized geometrical structures of studied compounds were calculated by B3LYP/6-311++ method. The atomic charges were calculated by Mulliken, NPA (natural population analysis), APT (atomic polar tensor), MK (Merz-Singh-Kollman method), and ChelpG (charges from electrostatic potentials using grid-based method) methods. Geometric as well as magnetic aromaticity indices, dipole moments, and energies were also calculated. The theoretical wavenumbers and intensities of IR spectra as well as chemical shifts in and NMR spectra were obtained. The calculated parameters were compared with experimental characteristics of these molecules.

Molecular Structural and Vibrational Spectroscopic Assignments of n5-(4-Methoxyphenyl)-3-(1-methylindol-3-yl)-isoxazole using DFT Theory Calculations

2019 ◽  
Vol 4 (3) ◽  
pp. 147-151
Author(s):  
J. Jani Matilda ◽  
T.F. Abbs Fen Reji
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Population Analysis ◽  
Nbo Analysis ◽  
Basis Set ◽  
Atomic Charges ◽  
Dft Methods ◽  
Mulliken Population ◽  
B3lyp Method ◽  
Experimental Values

In an effort to evaluate and design fast, accurate density functional theory (DFT) methods for 5-(4- methoxyphenyl)-3-(1-methylindol-3yl)isoxazole compound was done using Gaussion’ 09 program package using B3LYP method with the 6-31G basis set, which has been successfully applied in order to derive the optimized geometry, bonding features, harmonic vibrational wave numbers, NBO analysis and Mulliken population analysis on atomic charges in the ground state. Optimized geometries of the molecule have been described and collate with the experimental values. The experimental atomic charges demonstrates adequate concurrence with the theoretical prediction from DFT. The theoretical spectra values have been interpreted and compared with the FT-IR spectra. The calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gaps also confirm that charge transfer takes place within the molecule.

scholarly journals Molecular bending as a vital step toward transforming planar PAHs to fullerenes and tubular structures

2020 ◽  
Vol 644 ◽  
pp. A146
Author(s):  
Tao Chen ◽  
Yang Wang
Keyword(s):  
Density Functional ◽  
Intermolecular Forces ◽  
Molecular Structures ◽  
Intrinsic Reaction Coordinate ◽  
Functional Theory ◽  
B3lyp Method ◽  
Polycyclic Aromatic ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Hybrid Density Functional

Context. Polycyclic aromatic hydrocarbons (PAHs) and fullerenes are the largest molecules found in the interstellar medium (ISM). They are abundant and widespread in various astronomical environments. However, the detailed connection between these two species is unknown; in particular, no quantum chemical studies have been performed. Aims. In this work, we investigate a vital step in transforming planar PAHs to fullerenes, that is, the tubulation processes of PAHs. Methods. We used density functional theory for this study. The molecular structures and vibrational frequencies were calculated using the hybrid density functional B3LYP method. To better describe intermolecular forces, we considered Grimme’s dispersion correction in the calculations for this work. Intrinsic reaction coordinate calculations were also performed to confirm that the transition state structures are connected to their corresponding local potential energy surface minima. Results. As expected, we find that it is easier to bend a molecule as it gets longer, whereas it is harder to bend the molecule if it gets “wider” (i.e., with more rows of benzene rings). The change of multiplicity slightly alters the bending energies, while (a complete) dehydrogenation alleviates the bending barrier significantly and facilitates the formation of pentagons, which may act as an indispensable step in the formation of fullerenes in the ISM.

scholarly journals Quantum chemical studies on the molecular structure, spectroscopic and electronic properties of (6-Methoxy-2-oxo-2H-chromen-4-yl)-methyl pyrrolidine-1-carbodithioate

2016 ◽  
Vol 34 (4) ◽  
pp. 886-904 ◽  
Author(s):  
Meryem Evecen ◽  
Hasan Tanak
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Electronic Absorption Spectra ◽  
Chemical Shifts ◽  
Density Functional Theory Calculations ◽  
Molecular Geometry ◽  
Basis Set ◽  
Functional Theory ◽  
Hartree Fock ◽  
Chemical Studies

AbstractIn this paper, the molecular geometry, vibrational frequencies and chemical shifts of (6-Methoxy-2-oxo-2H-chromen-4-yl)methyl pyrrolidine-1-carbodithioate in the ground state have been calculated using the Hartree-Fock and density functional methods with the 6-311++G(d,p) basis set. To investigate the nonlinear optical properties of the title compound, the polarizability and the first hyperpolarizability were calculated. The conformational properties of the molecule have been determined by analyzing molecular energy properties. Using the time dependent density functional theory, electronic absorption spectra have been calculated. Frontier molecular orbitals, natural bond orbitals, natural atomic charges and thermodynamical parameters were also investigated by using the density functional theory calculations.

scholarly journals Molecular Structure and Quantum Chemical Calculations of 2, 4-difluoroanisole

2020 ◽  
Vol 8 (4S4) ◽  
pp. 125-130
Keyword(s):  
Molecular Structure ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Vibrational Analysis ◽  
1H And 13C Nmr ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Homo Lumo ◽  
Orbital Analysis ◽  
Ft Raman

FTIR / FT-Raman spectra in the regions 4000-400 cm-1 /3500-50 cm-1 are utilized for studying the molecular vibrations of 2,4-difluoroanisole (DFA). The optimized molecular structure and vibrational analysis of the DFA were estimated with the experimental as well as quantum chemical studies from ab initio and DFT calculations. The chemical shifts of 1H and 13C NMR were calculated. In addition, the thermodynamic and important electronic properties like HOMO-LUMO, NPA charge analyses have been examined. With the aid of NBO (Natural Bond Orbital) analysis, inter and intra molecular interactions are also illustrated.

X-ray and DFT Investigation of (E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol Compound

2018 ◽  
pp. 454-461
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Population Analysis ◽  
Diffraction Method ◽  
Dft Method ◽  
Basis Set ◽  
X Ray Diffraction ◽  
Mulliken Population ◽  
Charge Delocalization ◽  
X Ray

(E)-4-bromo-5-methoxy-2-((o-tolylimino)methyl)phenol was investigated by experimental and theoretical methodologies. The solid state molecular structure was determined by X-ray diffraction method. All theoretical calculations were performed by density functional theory (DFT) method by using B3LYP/6-31G(d,p) basis set. The titled compound showed the preference of enol form, as supported by X-ray diffraction method. The geometric and molecular properties were compaired for both enol-imine and keto-amine forms for title compound. Stability of the molecule arises from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond has been analyzed using natural bond orbital (NBO) analysis. Mulliken population method and natural population analysis (NPA) have been studied. Also, condensed Fukui function and relative nucleophilicity indices calculated from charges obtained with orbital charge calculation methods (NPA). Molecular electrostatic potential (MEP) and non linear optical (NLO) properties are also examined.

scholarly journals The Hydrogen Passivated Graphene Cluster and its Stability - First Principle DFT (B3LYP) Levels of Approximation with the Basis Set 3-21G

2018 ◽  
Vol 1 (1) ◽  
pp. 5-10
Author(s):  
Debendra Baniya
Keyword(s):  
Binding Energy ◽  
Carbon Atom ◽  
State Energy ◽  
Population Analysis ◽  
Basis Set ◽  
Mulliken Population ◽  
B3lyp Level ◽  
Reported Data ◽  
Homo Lumo ◽  
Graphene Cluster

First-principles DFT (B3LYP) levels of calculations with the basis set 3-21G have been carried out in order to study the geometric stability and electronic properties of hydrogen passivated graphene (H-graphene) clusters(CN) (where N = 6, 10, 13, 16, 22, 24, 27, 30, 35, 37, 40, 42, 45, 47, 48, 50, 52, 54, 70 and 96) and perform the DOS spectrum on H-graphene (C16H10, C24H12, C30H14, C48H18, C70H22 and C96H24) using Mulliken population analysis by the Gaussian 03 W set of programs. The variations of ground state energy of graphene clusters are observed on sizes and corresponding number of carbon atoms. The binding energy per carbon atom is the function of carbon atoms for the number of carbon atoms less than 30 and saturated at carbon’s number 30 and more in the DFT (B3LYP) levels of approximation with the basis set 3-21G. The binding energy per carbon atom of a pure graphene sheet C32 is 8.03 eV/atom in the DFT (B3LYP) level of approximation with the choice of the basis set 3-21G, which is acceptable with previous reported data 7.91 eV/atom. The HOMO-LUMO gap in NBO is studied for some H-grapheneclustors C16H10, C24H12, C30H14, C48H18, C70H22 and C96H24.

Population Analysis with Hydrogen 2 p Polarization Functions Included in the INDO Basis Set

1980 ◽  
Vol 35 (12) ◽  
pp. 1350-1353
Author(s):  
J. C. Facelli ◽  
R. H. Contreras
Keyword(s):  
Ab Initio ◽  
Population Analysis ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Mulliken Population Analysis ◽  
Indo Method ◽  
Hydrogen Atoms ◽  
Mulliken Population ◽  
Electron Population ◽  
Polarization Functions

Abstract Mulliken population analysis with 2p polarization functions included in the AO basis set of the INDO method has been performed for a set of molecules containing hydrogen as well as first row atoms. It is found that this enlargement of the basis set yields an increasing electron population in hydrogen atoms, in agreement with trends found in “ab initio” methods.

scholarly journals Quantum chemical investigation of spectroscopic, electronic and NLO properties of (1E, 4E)-1-(3-nitrophenyl)-5-phenylpenta-1,4-dien-3-one

2018 ◽  
Vol 6 (1) ◽  
pp. 121
Author(s):  
N Benhalima ◽  
S Yahiaoui ◽  
N Boubegra ◽  
M Boulakoud ◽  
Y Megrouss ◽  
...  
Keyword(s):  
Title Compound ◽  
Population Analysis ◽  
Energy Levels ◽  
Visible Spectrum ◽  
Molecular Geometry ◽  
Dft Method ◽  
Nbo Analysis ◽  
Basis Set ◽  
Vibrational Assignments ◽  
Reactivity Descriptors

In the present work the optimized molecular geometry and harmonic vibrational frequencies of chalcone derivative were calculated by DFT/B3LYP method with 6–31G (d,p) basis set. The vibrational assignments were performed on the basis of the potential energy dis-tribution (PED) of the vibrational modes. Natural bond orbital (NBO) analysis has been performed on title compound using B3LYP/6–31G (d,p) and HSEh1PBE /6–31G (d,p) levels in order to elucidate intermolecular hydrogen bonding, intermolecular charge transfer (ICT) and delocalization of electron density. Mulliken atomic charges, natural population analysis (NPA) and atomic polar tensors (APT) were performed. The nonlinear optical properties of the title compound are also calculated and discussed. Molecular electrostatic poten-tial and HOMO-LUMO energy levels are also computed. Ultraviolet–visible spectrum of the title compound has been calculated using TD–DFT method. The molecular orbital contributions were studied by density of states (DOSs). Global reactivity descriptors have been calculated using the HOMO and LUMO to predict compound reactivity.   

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