Molecular structure and vibrational spectra of 3-amino-5-hydroxypyrazole by density functional method

In this work, we report a combined experimental and theoretical study on molecular and vibrational structure of 3-amino-5-hydroxypyrazole (3A5HP). The Fourier transform infrared and Fourier transform Raman spectra of 3A5HP were recorded in the solid phase. The molecular geometry and vibrational frequencies of 3A5HP in the ground state have been calculated by using the density functional method B3LYP with basis sets, 6-311++G(d,p), 6-311+G(3df,2p), 6-311+G(3df,2pd), CC-pVDZ, aug-CC-pVDZ and CC-pVTZ. The optimized geometrical parameters obtained by B3LYP show best agreement with the experimental values. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.

X-ray crystallography characterization, vibrational spectroscopy, NMR spectra and quantum chemical DFT/HF study of N,N'-di(2-methoxyphenyl)formamidine

The title compound, N,N'-di(2-methoxyphenyl)formamidine (DMPF) was synthesized and characterized by FT-IR, FT-Raman, (1)H NMR, (13)C NMR spectroscopy and X-ray single crystal diffraction. The results show that the compound crystallizes in an orthorhombic system, with space group of Pbca and eight molecules in the unit cell. The unit cell parameters are: a=11.1118 (7)A, b=14.9878 (9)A and c=16.2851 (10)A. The molecular geometry, the normal mode frequencies and corresponding vibrational assignments of DMPF at the ground state were performed by HF and B3LYP methods with 6-311+G(d,p) basis set. It was observed that the bond lengths and angles in the molecule, obtained by X-ray at the level of theory, were in good agreement with those of the experiment. A detailed interpretation of the infrared and Raman spectra of DMPF was reported. The (13)C NMR and (1)H NMR of DMPF have been calculated using HF and B3LYP methods with 6-311+G(d,p) basis set. Comparison between experimental and theoretical results showed that B3LYP/6-311+G(d,p) method is able to provide more satisfactory results for predicting IR, Raman, (1)H NMR and (13)C NMR properties.

FT-Raman and FTIR spectra, assignments and ab initio calculations of 2-aminobenzyl alcohol

The Fourier transform Raman and Fourier transform infrared spectra of 2-aminobenzyl alcohol (2ABA) were recorded in the solid phase. Geometry optimizations were done with out any constraint and harmonic vibrational wave numbers and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and DFT levels invoking 6-31g** and 6-311+g(2d, p) basis sets and the results were compared with the experimental values. With the help of three specific scaling procedures, the observed vibrational wavenumbers in FTIR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range and the error obtained was in general very low. The appropriate theoretical spectrograms for the Raman and IR spectra of 2ABA were also constructed.

Molecular structure, vibrational spectroscopic (FT-IR, FT-Raman), UV and NBO analysis of 2-chlorobenzonitrile by density functional method

In this work, we will report a combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV spectral analysis of 2-chlorobenzonitrile (2-ClBN). The FT-IR solid phase (4000-400 cm(-1)), and FT-Raman spectra (3500-50 cm(-1)) of 2-ClBN was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2-ClBN in the ground state have been calculated by using the density functional methods (BLYP, B3LYP) with 6-31G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* anti bonding orbitals and E2 energies confirms the occurrence of ICT (Intra molecular Charge Transfer) within the molecule. The UV spectrum was measured in ethanol solution. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. Finally calculated results were applied to simulated Infrared and Raman spectra of the title compound which show good agreement with observed spectra.

FT-IR, FT-Raman spectra and ab initio DFT vibrational analysis of p-bromophenoxyacetic acid

The Fourier transform Raman and Fourier transform infrared spectra of p-bromophenoxyacetic acid were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by HF and DFT (B3LYP) method with the 6-31G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental ones. A detailed interpretation of the infrared and Raman spectra of p-bromophenoxyacetic acid is reported on the basis of the calculated potential energy distribution. The theoretical spectrograms for the IR spectrum of the title molecule have been constructed.

Molecular structure and vibrational spectra of Irinotecan: a density functional theoretical study

The solid phase FTIR and FT-Raman spectra of Irinotecan have been recorded in the regions 400-4000 and 50-4000 cm(-1), respectively. The spectra were interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d) as basis set. The vibrational frequencies were calculated for Irinotecan by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared spectrum was also simulated from the calculated intensities. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

FT-IR, FT-Raman spectra and ab initio HF, DFT vibrational analysis of p-chlorobenzoic acid

The infrared, the Fourier transform infrared and Fourier transform Raman spectra of p-chlorobenzoic acid (p-CBA) has been recorded in the region 4000-600 cm(-1), 4000-400 cm(-1) and 4000-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of p-CBA were obtained by the ab initio HF and DFT (B3LYP) methods with complete relaxation in the potential energy surface using 6-311+G(d,p) basis set. The harmonic-vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

The spectroscopic (FT-IR, FT-Raman), NCA, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of L-cysteine by ab inito HF and density functional method

In this work, we report a combined experimental and theoretical study on molecular structure (monomer, dimer), vibrational spectra, and Natural Bond Orbital (NBO) analysis of non-ionized L-cysteine (LCY). The FT-IR solid phase (4000-400 cm(-1)) and FT-Raman spectra (3500-50 cm(-1)) of LCY was recorded at room temperature. The molecular geometry, harmonic and anharmonic vibrational frequencies and bonding features of LCY in the ground state have been calculated by using the density functional method (B3LYP) with 6-311G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the Scaled Quantum Mechanical Force Field (SQMFF) methodology. The first order hyperpolarizability (β(0)) of this novel molecular system and related properties (β, α(0) and Δα) of LCY are calculated using HF/6-311G(d,p) method on the finite-field approach. Stability of the molecule has been analyzed using NBO analysis. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculations results were applied to stimulate infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Experimental and theoretical spectroscopic studies of anticancer drug rosmarinic acid using HF and density functional theory

In this work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of anticancer drug of rosmarinic acid. The optimized molecular structure, atomic charges, vibrational frequencies, natural bond orbital analysis and ultraviolet-visible spectral interpretation of rosmarinic acid have been studied by performing HF and DFT/B3LYP/6-31G(d,p) level of theory. The FT-IR (solid and solution phase), FT-Raman (solid phase) spectra were recorded in the region 4000-400 and 3500-50 cm(-1), respectively. The UV-Visible absorption spectra of the compound that dissolved in ethanol were recorded in the range of 200-800 nm. The scaled wavenumbers are compared with the experimental values. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The formation of hydrogen bond was investigated in terms of the charge density by the NBO calculations. Based on the UV spectra and TD-DFT calculations, the electronic structure and the assignments of the absorption bands were carried out. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

FTIR, FT-Raman spectra and ab initio DFT vibrational analysis of 2-amino-5-chloropyridine

The FTIR and FT-Raman spectra of 2-amino-5-chloropyridine (ACP) has been recorded in the region 4000-400 and 3500-100 cm-1, respectively. The optimized geometry, frequency and intensity of the vibrational bands of ACP were obtained by the ab initio and density functional theory (DFT) levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) and 6-311+G(2df,2p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

One-pot synthesis, FT-IR, NMR and density functional method (B3LYP) studies on 2-(cyclohexylamino)-2-oxo-1-(pyridin-2-yl)ethyl benzoate

2-(Cyclohexylamino)-2-oxo-1-(pyridin-2-yl)ethyl benzoate has been synthesized and characterized by elemental analysis, FT-IR, (1)H NMR and (13)C NMR. Geometrical structures, vibrational frequencies, (1)H and (13)C chemical shift values, molecular electrostatic potential maps and several thermodynamic parameters of title compound in the ground state have been calculated by using the density functional method with 6-31G(d) basis set. The IR spectrum of title compound was interpreted in terms of potential energy distribution (PED) analysis and NMR chemical shifts were also simulated using the GaussView program. Comparison of the theoretical vibrational spectra, (1)H and (13)C NMR chemical shifts of title compound showed a good agreement with the experimental data.

Synthesis, X-ray crystallography characterization, vibrational spectroscopic, molecular electrostatic potential maps, thermodynamic properties studies of N,N'-di(p-thiazole)formamidine

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of N,N'-di(p-thiazole)formamidine (DpTF). DpTF has been synthesized and characterized by elemental analysis, FT-IR, FT-Raman, 1H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The FT-IR and FT-Raman spectra of DpTF were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d) basis set. The FT-IR and FT-Raman spectra of DpTF was calculated at the HF/B3LYP/6-31G(d) level and were interpreted in terms of potential energy distribution (PED) analysis. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of DpTF was reported. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m°, Sm°, Hm° and temperatures. Furthermore, molecular electrostatic potential maps (MESP) and total dipole moment properties of the compound have been calculated.

Experimental (FTIR and FT-Raman) and ab initio and DFT study of vibrational frequencies of 5-amino-2-nitrobenzoic acid

The FTIR and FT-Raman spectra of 5-amino-2-nitrobenzoic acid (ANB) have been recorded in the region 400-4000 cm(-1). The observed frequencies were assigned to different modes of vibrations on the basis of fundamental, combination and overtones. The geometry has been optimized with complete relaxation on the potential energy surface at HF, MP2 and B3LYP level of theories using 6-311++G(d,p) basis set and compared with the crystal data. The possible hydrogen bond interaction has been estimated taking a model compound. Further harmonic vibrational frequency calculations have been carried out at HF and B3LYP levels and the scaled values were in good agreement with majority of the experimental observations. The theoretically constructed spectra coincide satisfactorily with those of experimental spectra.

Quantum mechanical and spectroscopic (FT-IR, FT-Raman, 13C, 1H and UV) investigations of antiepileptic drug Ethosuximide

The Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of antiepileptic drug Ethosuximide (ETX) have been recorded and analyzed. In addition, the IR spectra in CCl(4) at various concentrations of ETX are also recorded. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of Density Functional Theory (DFT) method. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge Including Atomic Orbital (GIAO) method. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the σ* and π* antibonding orbitals and second order delocalization energies E(2) confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies, were performed by Time-Dependent Density Functional Theory (TD-DFT) approach. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with observed spectra.

Synthesis and spectroscopic characterization on 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid: A DFT approach

A complete structural and vibrational analysis of the 4-(2,5-di-2-thienyl-1H-pyrrol-1-yl) benzoic acid (TPBA), was carried out by ab initio calculations, at the density functional theory (DFT) method. Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) (13)C NMR and (1)H NMR chemical shift values of (TPBA), in the ground state have been calculated by using ab initio density functional theory (DFT/B3LYP) method with 6-311G(d,p) as basis set for the first time. Comparison of the observed fundamental vibrational modes of (TPBA) and calculated results by DFT/B3LYP method indicates that B3LYP level of theory giving yield good results for quantum chemical studies. Vibrational wavenumbers obtained by the DFT/B3LYP method are in good agreement with the experimental data. The study was complemented with a natural bond orbital (NBO) analysis, to evaluate the significance of hyperconjugative interactions and electrostatic effects on such molecular structure. By using TD-DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental one is determined. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals analysis and thermodynamic properties of TPBA were investigated using theoretical calculations.

Vibrational spectra and assignments of 3-aminobenzyl alcohol by ab initio Hartree-Fock and density functional method

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of 3-aminobenzyl alcohol. The FT-Raman and FT-IR spectra of 3-aminobenzyl alcohol were recorded in the solid phase. The equilibrium geometry, harmonic vibrational frequencies, infrared intensities, Raman scattering activities, depolarization ratios and reduced masses were calculated by ab initio HF and density functional B3LYP method with 6-311+G(d,p) basis sets. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The thermodynamic functions of the title compound were also performed at HF/6-311+G(d,p) and B3LYP/6-311+G(d,p) levels of theory. A detailed interpretation of the infrared and Raman spectra of 3-aminobenzyl alcohol is reported. The theoretical spectrograms for FT-IR spectra of the title molecule have been constructed.

Vibrational spectra and quantum chemical calculations of 3,4-diaminobenzoic acid

The Fourier Transform Raman and Fourier Transform infrared spectra of 3,4-diaminobenzoic acid (3,4-DABA) were recorded in the solid phase. Geometry optimizations were done without any constraint and harmonic-vibrational wave numbers and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and DFT levels invoking 6-311++G(d,p) basis set. The results were compared with the experimental values with the help of specific scaling procedures, the observed vibrational wavenumbers in FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range, the error obtained was in general very low. The appropriate theoretical spectrograms for the IR and Raman spectra of the title molecule were also constructed.

FTIR, FT-Raman spectra and ab initio DFT vibrational analysis of 2,4-dichloro-6-nitrophenol

The FTIR and FT-Raman spectra of 2,4-dichloro-6-nitrophenol (2,4-DC6NP) has been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of (2,4-DC6NP) were obtained by the ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) and 6-311+G(d,p) basis sets. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

Synthesis, structural and spectral analysis of (E)-N'-(4-Methoxybenzylidene)pyridine-3-carbohydrazide dihydrate by density functional theory

New nonlinear optical crystal, (E)-N'-(4-Methoxybenzylidene)pyridine-3-carbohydrazide dihydrate (MBP3CD 2H2O) has been synthesized and grown as a single crystal by the slow evaporation solution growth technique. The compound was characterized by FTIR (4000-400 cm(-1)), FT-Raman (3500-50 cm(-1)) and UV-Vis (800-200 nm) spectroscopy. The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of MBP3CD 2H2O have been investigated experimentally and theoretically using Gaussian03 software package were performed using B3LYP method with the 6-31G(d,p) basis set. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using Natural Bond Orbital (NBO) analysis. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of nonlinear optics. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. In addition, molecular electrostatic potential (MEP), frontier molecular orbital (FMO) analysis were investigated using theoretical calculations. The chemical reactivity and thermodynamic properties (heat capacity, entropy and enthalpy) of MBP3CD 2H2O at different temperature are calculated.

The spectroscopic (FT-IR, FT-Raman, UV and NMR) first order hyperpolarizability and HOMO-LUMO analysis of dansyl chloride

The solid phase FT-IR and FT-Raman spectra of dansyl chloride (DC) have been recorded in the regions 400-4000 and 50-4000 cm(-1), respectively. The spectra have been interpreted in terms of fundamentals modes, combination and overtone bands. The structure of the molecule has been optimized and the structural characteristics have been determined by density functional theory (B3LYP) method with 6-311++G(d,p) as basis set. The vibrational frequencies were calculated for most stable conformer and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra have also been predicted from the calculated intensities. (1)H and (13)CNMR spectra were recorded and (1)H and (13)C nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-Visible spectrum of the compound was recorded in the region 200-600 nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Nonlinear optical and thermodynamic properties were interpreted. All the calculated results were compared with the available experimental data of the title molecule.