scholarly journals Computational Studies of Vibration Spectra and Thermodynamic Properties of Metformin Using HF, DFT Methods

2011 ◽  
Vol 8 (1) ◽  
pp. 165-172
Author(s):  
S. Srinivasan ◽  
V. Renganayaki
Keyword(s):  
Fourier Transform ◽  
Thermodynamic Properties ◽  
Vibrational Energy ◽  
Solid Phase ◽  
Optimization Procedure ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Dependent Diabetes Mellitus ◽  
Dft Methods ◽  
Experimental Values

The molecular vibrations of metformin, one of the important anti-diabetic drugs to treat Non Insulin Dependent Diabetes Mellitus (NIDDM) have been investigated at room temperature by Fourier transform infrared (FTIR) and Fourier transform Raman (FTR) spectroscopies. The solid phase FTIR and FT-Raman spectra of the title compound have been recorded in the regions 4000-400 and 3500-250 cm-1. A satisfactory band assignment has been made on the fundamental modes of vibration. Employing the ab - initio Hatree –Fock (HF) and Density Function Theory (DFT) methods, the theoretical vibrational frequencies and geometry parameters like bond lengths, bond angles etc have been calculated and compared with the experimental values. HF and DFT calculations were performed using the standard B3LYP/6-31G** method and basis set combination. Optimized geometries were obtained using the global optimization procedure. Theoretical investigations of harmonic vibrational frequencies and thermodynamic properties viz. the zero point vibrational energy (ZPVE), entropy, heat capacity have been carried out. It has been found that both methods gave consistent data for geometric parameters, but DFT yielded vibrational frequencies much closer to the experimental values.

scholarly journals Predictive calculation of structural, nonlinear optical, electronic and thermodynamic properties of andirobin molecule from ab initio and DFT methods

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
M. T. Ottou Abe ◽  
C. L. Nzia ◽  
L. Sidjui Sidjui ◽  
R. A. Yossa Kamsi ◽  
C. D. D. Mveme ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Energy Gap ◽  
Basis Set ◽  
Dft Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
H Nmr ◽  
Experimental Values

AbstractThe structural, nonlinear optical, electronic and thermodynamic properties of andirobin molecule were carried out by density functional theory at the B3LYP, WB97XD level and at the Restricted Hartree–Fock level by employing 6–311G(d,p) basis set. The obtained values of bond lengths, bond angles, 1H NMR and 13C NMR are in good agreement with experimental values. The dipole moment and first static hyperpolarizability show that andirobin can be applied in nonlinear optical devices. HOMO–LUMO energy gap values were found to be greater than 4 eV and lead us to the conclusion that this molecule can be used as insulator in many electronic devices. The thermal energy (E), molar heat capacity at constant volume $$(C_{v}$$ ( C v ) and entropy (S) were also calculated.

scholarly journals DEVELOPMENT OF MOLECULAR IMPRINTED POLYMER SOLID PHASE EXTRACTION (MISPE) FOR SEPARATION NITROFURANTOIN RESIDUE IN CHICKEN EGGS

2017 ◽  
Vol 10 (6) ◽  
pp. 108
Author(s):  
Sophi Damayanti ◽  
Untung Gunawan ◽  
Slamet Ibrahim
Keyword(s):  
Solid Phase Extraction ◽  
Analytical Methods ◽  
Density Functional ◽  
Solid Phase ◽  
Basis Set ◽  
Phase Extraction ◽  
Molecular Imprinted Polymer ◽  
Imprinted Polymer ◽  
Dft Methods ◽  
The Matrix

Background: The use of nitrofurantoin and other nitrofuran antibiotics in food which produced from animals is prohibited by European Union because of potentially carcinogenic and mutagenic. Various methods for analysis of residues of nitrofurantoin has been developed, but because of the interference of the matrix, it is necessary to separate the matrix therefore, the matrix effect will not interfere the analysis. Nowadays, molecular imprinted polymer (MIP) is a well-developed tool in the analytical field, mainly for separating substances in relatively complex matrices.Objective: The purpose of this study is to obtain MISPE that is selective for the separation of nitrofurantoin residues in chicken eggs.Methods: Analytical methods development of nitrofurantoin were optimization of HPLC system and validation of analytical methods performed to obtain the suitable system for nitrofurantoin detection. In silico study used for MIP design by observing the difference Gibbs free energy using Gaussview 5.08 software with Density Functional Theory (DFT) methods using 6-311G as basis set. MIP synthesis was done using bulk method use nitrofurantoin as template, acrylamide as functional monomer, ethyleneglycoldimethacrylate (EGDMA) as crosslinker, and azobisisobutyronitrile (AIBN) as an initiator reaction inside dimethylformamide (DMF) as solvent. Non imprinted polymer (NIP) was synthesized as comparison. MIP and NIP which has been synthesized was inserted into SPE cartridge and characterized using Infrared spectroscopy and HPLC.Result: MISPE that has been synthesized was characterized and compared to non-imprinted polymer solid phase extraction (NISPE) and marketed Solid Phase Extraction (SPE) C18. Sensitivity of MIP, NIP, and SPE C-18 to nitrofurantoin was 84.54 %, 37.73 %, and 33.95 % respectively, based on recovery of nitrofurantoin.Conclusion: Based on the result it was obtained MISPE has high selectivity toward nitrofurantoin compared to NISPE and either marketed SPE.  

scholarly journals Molecular Structure and Vibrational Analysis of 1-Bromo-2-Chlorobenzene Using ab initio HF and Density Functional Theory (B3LYP) Calculations

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
G. Shakila ◽  
S. Periandy ◽  
S. Ramalingam
Keyword(s):  
Density Functional ◽  
Vibrational Analysis ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Geometrical Parameters ◽  
B3lyp Method ◽  
B3lyp Calculations ◽  
Ft Ir ◽  
Experimental Values ◽  
Ft Raman

The FT-Raman and FT-IR spectra for 1-bromo-2-chlorobenzene (1B2CB) have been recorded in the region 4000–100 cm−1 and compared with the harmonic vibrational frequencies calculated using HF/DFT (B3LYP) method by employing 6-31+G (d, p) and 6-311++G (d, p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values of some substituted benzene. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. The scaled vibrational frequencies at B3LYP/6-311++G (d, p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. Some of the vibrational frequencies of the benzene are affected upon profusely with the halogen substitutions in comparison to benzene, and these differences are interpreted.

scholarly journals Spectroscopic Investigations and DFT Calculations on 3-(Diacetylamino)-2-ethyl-3H-quinazolin-4-one

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Yusuf Sert ◽  
Fatih Ucun ◽  
Gamal A. El-Hiti ◽  
Keith Smith ◽  
Amany S. Hegazy
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Solid Phase ◽  
Vibrational Frequencies ◽  
Geometric Parameters ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Laser Raman ◽  
Quantum Chemical Methods ◽  
Lowest Unoccupied Molecular Orbital

The theoretical and experimental vibrational frequencies of 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) were investigated. The experimental Laser-Raman spectrum (4000–100 cm−1) and FT-IR spectrum (4000–400 cm−1) of the newly synthesized compound were recorded in the solid phase. Both the theoretical vibrational frequencies and the optimized geometric parameters such as bond lengths and bond angles have for the first time been calculated using density functional theory (DFT/B3LYP and DFT/M06-2X) quantum chemical methods with the 6-311++G(d,p) basis set using Gaussian 03 software. The vibrational frequencies were assigned with the help of potential energy distribution (PED) analysis using VEDA 4 software. The calculated vibrational frequencies and the optimized geometric parameters were found to be in good agreement with the corresponding reported experimental data. Also, the energies of the lowest unoccupied molecular orbital (LUMO), highest occupied molecular orbital (HOMO), and other related molecular energies for 3-(diacetylamino)-2-ethyl-3H-quinazolin-4-one (2) have been investigated using the same computational methods.

scholarly journals FT-IR, FT-Raman, Homo-Lumo and UV-Visible Spectral Analysis of E-(N′-(1H-INDOL-3YL) Methylene Isonicotinohydrazide)

2017 ◽  
Vol 1 (3) ◽  
pp. 1-37
Author(s):  
D. Sumathi ◽  
H. Saleem ◽  
A. Nathiya ◽  
N. RameshBabu ◽  
D. Usha
Keyword(s):  
Energy Gap ◽  
Solid Phase ◽  
Basis Set ◽  
Excitation Energies ◽  
B3lyp Method ◽  
Td Dft ◽  
Ft Ir ◽  
Experimental Values ◽  
Homo Lumo ◽  
Ft Raman

A combined experimental and theoretical study on molecular and vibrational structure of E-N¢ (ICINH) had been carried out. The FTIR, FT-Raman and UV-Vis spectra of ICINH were recorded in the solid phase. The optimized geometry was calculated by B3LYP method with 6-311++G(d,p) level of basis set. The harmonic vibrational frequencies, IR intensities and Raman scattering activities of the title compound were calculated at same level of theory. The scaled theoretical wavenumber showed very good agreement with the experimental values. The mulliken charges and thermodynamic functions of the ICINH were also performed at same level of theory. NLO and a study on the electronic properties such as excitation energies and wavelength, were performed by TD-DFT approach. HOMO–LUMO energy gap was also calculated and interpreted.

scholarly journals An investigation of the excitation and emission properties of fluorescence compounds using DFT and TD-DFT methods

2018 ◽  
Vol 127 (1A) ◽  
pp. 43
Author(s):  
Duong Tuan Quang
Keyword(s):  
Density Functional Theory ◽  
Excited States ◽  
Density Functional ◽  
Basis Set ◽  
Excitation Energies ◽  
Dft Methods ◽  
Functional Theory ◽  
Emission Properties ◽  
Experimental Values ◽  
Optimized Geometries

<p class="03Abstract">The density functional theory and time-dependent density functional theory methods were used for investigation of the excitation and emission properties of some fluorophores. The calculations were based on the optimized geometries of ground states and excited states at the B3LYP functional and LanL2DZ basis set. The results clarified the nature of the optical properties of the compounds and agreed well with the experimental data. The approximate values of excitation energies and emission energies of compounds were also identified. The calculated excitation energies were about 0.01 to 0.56 eV higher than experimental values. Meanwhile, the emission energies were from 0.34 to 0.89 eV higher than experimental values. These large errors occurred when there were great variations between the optimized geometries of ground state and excited states. They could be due to the presence of components of solvent in real solution that stabilized the excited states, leading to reduce the excitation and emission energies in the experiments.</p>

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 Theoretical investigations on the structural, spectroscopic, electronic and thermodynamic properties of (3-Oxo-3H-benzo[f]chromen-1yl) methyl N,N-dimethylcarbamodithioate-1ex

2017 ◽  
Vol 35 (3) ◽  
pp. 560-575
Author(s):  
Mehmet Kara ◽  
Meryem Evecen ◽  
Telhat Özdogan
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Structural Parameters ◽  
Atomic Charge ◽  
Basis Set ◽  
Torsional Angle ◽  
Hartree Fock ◽  
Homo And Lumo ◽  
Charge Analysis ◽  
Experimental Values

AbstractHartree-Fock and Density Functional Theory (B3LYP, B3PW91) calculations for the ground state of (3-Oxo-3Hbenzo[ f]chromen-1-yl) methyl N,N-dimethylcarbamodithioate have been presented and the calculated structural parameters and energetic properties have been compared with the available X-ray diffraction data. The vibrational frequencies have been calculated using optimized geometry of the molecule. The conformational properties of the molecule have been determined by computing molecular energy properties, in which torsional angle varied from -180° to +180° in steps of 10°. Moreover, natural bond orbital analysis and atomic charge analysis have been performed. Besides, HOMO and LUMO energies have been calculated and their pictures have been presented. Finally, molecular electrostatic potential and thermodynamic properties have been calculated. It is seen that the obtained theoretical results agree well with the available experimental values. In all the calculations, except for optimization and vibrational calculations, B3LYP level of theory with 6-311++G(d,p) basis set has been used.

scholarly journals On the Relevance of Considering the Intermolecular Interactions on the Prediction of the Vibrational Spectra of Isopropylamine

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Ana M. Amado ◽  
Sónia M. Fiuza ◽  
Luis A. E. Batista de Carvalho ◽  
Paulo J. A. Ribeiro-Claro
Keyword(s):  
Hydrogen Bonding ◽  
Weak Interactions ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Vibrational Modes ◽  
Dft Methods ◽  
Torsional Mode ◽  
Computational Costs ◽  
Donor And Acceptor ◽  
The Comparative Study

The effects of implicitly considering the effects of hydrogen bonding on the molecular properties, such as vibrational frequencies, were inferred on the basis of DFT calculations. Several clusters of isopropylamine were assembled and theoretically characterized. The results showed that maximum H-bond cooperativity is achieved when the amine group acts simultaneously as donor and acceptor. The effect of H-bond cooperativity manifests itself in the relative cluster stability and on the structural and vibrational frequency predictions. Referring to the vibrational frequencies it was found that theNH2stretching and torsion vibrational modes are the most affected by the amine involvement in hydrogen bonding. Both stretching modes were found to be significantly redshifted relative to the monomer. TheNH2torsional mode, on the other hand, was found to be blueshifted up to 350 cm-1. Finally, the comparative study between the theory levels performed allows to conclude that the small 6-31G* basis set is able to stabilize weakC–H⋯Ninteractions as long as the new dispersion corrected DFT methods are considered. The impairments observed with conventional DFT methods for describing weak interactions may be overcome with the improvement of basis set, but the associated increase of computational costs may turn the calculations unfeasible.

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