N. Sundaraganesan

The spectroscopic (FT-IR, FT-IR gas phase, FT-Raman and UV) and NBO analysis of 4-Hydroxypiperidine by density functional method.

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational spectra, NBO and UV-spectral analysis of 4-Hydroxypiperidine (4-HP). The FT-IR solid phase (4000-400 cm(-1)), FT-IR gas phase (5000-400 cm(-1)) and FT-Raman spectra (3500-50 cm(-1)) of 4-HP was recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 4-HP in the ground-state have been calculated by using the density functional methods (BLYP, 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 Methodology (SQMFF). Stability of the molecule arising from hyperconjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the sigma* antibonding orbitals and E (2) 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) result complements the experimental findings. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulated infrared and Raman spectra of the title compound which show good agreement with observed spectra.

Molecular structure, spectroscopic (FT-IR, FT-Raman, NMR, UV) studies and first-order molecular hyperpolarizabilities of 1,2-bis(3-methoxy-4-hydroxybenzylidene)hydrazine by density functional method.

Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 1,2-bis(3-methoxy-4-hydroxybenzylidene)hydrazine [vanillin azine (VA)] were carried out by using density functional (DFT/B3LYP) method with 6-31G(d) as basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The vibrational spectral data obtained from solid phase FT-IR and FT-Raman spectra are assigned based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with calculated values. The electric dipole moment (mu) and the first hyperpolarizability (beta) values of the investigated molecule have been computed using ab initio quantum mechanical calculations. The calculation results also show that the VA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. A detailed interpretation of the infrared and Raman spectra of VA was also reported. 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 show that charge transfer occurs within the molecule. The theoretical NMR chemical shifts complement with experimentally measured ones.

Molecular structure and vibrational spectra of 3-chloro-4-fluoro benzonitrile by ab initio HF and density functional method.

In this work, the experimental and theoretical spectra of 3-chloro-4-fluoro benzonitrile (3C4FBN) were studied. The Fourier transform infrared and Fourier transform Raman spectra of 3C4FBN were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods with 6-311++G(d,p) basis set. The harmonic-vibrational frequencies, infrared intensities and Raman scattering activities of the title compound were performed at and HF/B3LYP/6-311++G(d,p) level of theories. The scaled theoretical wave number showed very good agreement with the experimental values. The thermodynamic functions of the title compound was also performed at HF/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the infrared and Raman spectra of 3C4FBN was reported. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.

FT-IR, FT-Raman, NMR and UV–vis spectra, vibrational assignments and DFT calculations of 4-butyl benzoic acid

The solid phase FTIR and FT-Raman spectra of 4-butyl benzoic acid (4-BBA) have been recorded in the regions 400-4000 and 50-4000cm(-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 6-311++G(d,p) as basis set. The vibrational frequencies were calculated for monomer and dimer by DFT method and were compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. (13)C and (1)H NMR spectra were recorded and (13)C and (1)H 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 200-400nm and the electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. The geometric parameters, energies, harmonic vibrational frequencies, IR intensities, Raman intensities, chemical shifts and absorption wavelengths were compared with the available experimental data of the molecule.

Experimental FTIR, FT-IR (gas phase), FT-Raman and NMR spectra, hyperpolarizability studies and DFT calculations of 3,5-dimethylpyrazole.

In the present study, structural properties of 3,5-dimethylpyrazole (3,5-DMP) have been studied extensively utilizing density functional theory (DFT) employing B3LYP exchange correlation. The Fourier transform infrared (solid phase and gas phase) and Fourier transform Raman spectra of 3,5-DMP were recorded. The Vibrational frequencies of 3,5-DMP in the ground state have been calculated by using density functional method (B3LYP) with 6-31G(d,p), 6-311G(d,p) and 6-311++G(d,p) as basis sets. Comparison of the observed fundamental vibrational frequencies of 3,5-DMP with calculated results show that 6-311++G(d,p) superior to other basis sets for molecular vibrational problems. Non linear optical NLO behavior of the examined molecule was investigated by the determination of the electric dipole moment mu, the polarizability alpha and the hyperpolarizability beta using the B3LYP/cc-pvdz method. The isotropic chemical shifts computed by (13)C and (1)H NMR analysis also show good agreement with experimental observations. The theoretically predicted FTIR and FT-Raman spectra of the title molecule have been constructed.

The spectroscopic (FTIR, FT-IR gas phase and FT-Raman), first order hyperpolarizabilities, NMR analysis of 2,4-dichloroaniline by ab initio HF and density functional methods.

In this work, the experimental and theoretical study on molecular structure and vibrational spectra of 2,4-dichloroaniline (2,4-DCA) were studied. The Fourier transform infrared (gas phase) and Fourier transform Raman spectra of 2,4-DCA were recorded. The molecular geometry and vibrational frequencies of 2,4-DCA in the ground state were calculated by using the Hartree-Fock (HF) and density functional (DF) methods (BLYP, B3LYP and SVWN) with 6-31G(d,p) as basis set. Comparison of the observed fundamental vibrational frequencies of 2,4-DCA with calculated results by HF and density functional methods indicates that BLYP is superior to other methods for molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small. The electric dipole moment (micro) and the first hyperpolarizability (beta) values of the investigated molecule were computed using ab initio quantum mechanical calculations. The calculated results also show that the 2,4-DCA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Natural atomic charges of 2,4-DCA and 4-chloroaniline was calculated and compared. The isotropic chemical shift computed by (13)C NMR analyses also shows good agreement with experimental observations. The theoretically predicted FTIR and FT-Raman spectra of the title molecule have been constructed.

Molecular structure, spectroscopic studies and first-order molecular hyperpolarizabilities of ferulic acid by density functional study

Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of ferulic acid (FA) (4-hydroxy-3-methoxycinnamic acid) were carried out by using density functional (DFT/B3LYP/BLYP) method with 6-31 G(d,p) as basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The vibrational spectral data obtained from solid phase FT-IR and FT-Raman spectra are assigned based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with calculated values. The electric dipole moment (micro) and the first hyperpolarizability (beta) values of the investigated molecule have been computed using ab initio quantum mechanical calculations. The calculation results also show that the FA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. A detailed interpretation of the infrared and Raman spectra of FA was also reported. 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 shows that charge transfer occur within the molecule. The theoretical FT-IR and FT-Raman spectra for the title molecule have been constructed.

Molecular structure, anharmonic vibrational frequencies and NBO analysis of naphthalene acetic acid by density functional theory calculations

In this work, we report anharmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of naphthalene acetic acid (NAA). The optimized geometric bond lengths and bond angles obtained by computation show good agreement with experimental X-ray data. The computed dimer parameters also show good agreement with experimental data. Anharmonic frequencies of NAA were determined and analyzed by DFT level of theory utilizing 6-311+G(d,p) basis set. Good agreement between the calculated and experimental spectra was obtained. Stability of the molecule arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The results show that charge in electron density (ED) in the pi* and sigma* antibonding orbitals and E2 energies. This confirms the occurrence of ICT (Intermolecular Charge Transfer) within the molecule. The calculated HOMO and LUMO energies also show that charge transfer occurs within the molecule.

FT-IR, FT-Raman, NMR spectra and DFT calculations on 4-chloro-N-methylaniline

In this work, the vibrational spectral analysis was carried out by using FT-IR and FT-Raman spectroscopy in the range 400-4000 and 50-3500cm(-1) respectively, for the title molecule. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method using 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments of all the vibrational mode were performed on the basis of the total energy distributions (TED). (13)C and (1)H NMR chemical shifts results were given and are in agreement with the corresponding experimental values. The theoretically constructed FT-IR and FT-Raman spectra exactly coincides with experimental one.

Molecular structure, vibrational, UV and NBO analysis of 4-chloro-7-nitrobenzofurazan by DFT calculations.

In the present work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and NBO analysis of 4-chloro-7-nitrobenzofurazan (NBD-Chloride). The FT-IR (400-4000 cm(-1)) and FT-Raman spectra (50-4000 cm(-1)) of NBD-Chloride were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of NBD-Chloride in the ground-state have been calculated by using the density functional B3LYP method with 6-311++G (d, p) as higher basis set. The energy and oscillator strength calculated by time-dependent density functional theory (TD-DFT) result in DMSO and CDCl3 solvents complements with each other. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. Finally the calculation results were applied to simulate infrared and Raman spectra of the title compound which show good agreement with observed spectra.