Non-hormonal isoflavone derivative 7-Isopropoxy-3-phenyl-4H-1-benzopyran-4-one (7I3P4H) is used f... more Non-hormonal isoflavone derivative 7-Isopropoxy-3-phenyl-4H-1-benzopyran-4-one (7I3P4H) is used for prevention and treatment of postmenopausal osteoporosis. It is also used for reducing bone loss caused by chronic kidney diseases and paralysis associated with stroke. Optimized geometry and Natural Bond Orbital (NBO) analysis of 7I3P4HB carried out to demonstrate the various intra-molecular interactions that are responsible for the stabilization of this molecule leading to its medicinal activity. Ultraviolet Absorption (UV) spectra have been recorded and analyzed. Energy gap has been calculated from Frontier Molecular Orbital Analysis with the help of B3LYP/6-311++G (d, p) method.
Naphthalene 2-sulfonic acid (NSA) and its derivatives are the most important class of organic com... more Naphthalene 2-sulfonic acid (NSA) and its derivatives are the most important class of organic compounds and are important products of industrial chemical processes.. Bioactive molecule NSA was performed by means of Density Functional Theoretical (DFT) method using standard B3LYP/6-31G (d,p) basis set implemented with Gaussian'09 software package. NBO analysis were performed to provide valuable information about various intermolecular interactions. Optical properties of the NSA molecule were studied using UV-Vis spectral analysis. In addition, Molecular docking was performed for the different receptors for calculating binding affinities and predicting binding sites.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
The IR and Raman spectra of 3,5-dichlorobenzonitrile (3,5-DCBN) molecule were recorded at room te... more The IR and Raman spectra of 3,5-dichlorobenzonitrile (3,5-DCBN) molecule were recorded at room temperature and then the assignment of the observed fundamental bands were achieved by the aid of the theoretical vibrational spectral data obtained from a quantum chemical study carried out for the free molecule case. In the calculations performed to determine the molecular geometry, vibrational spectral data and thermodynamic parameters, Møller-Plesset second order perturbation theory (MP2) and hybrid Density Functional Theory (DFT) types of electronic structure methods, B3LYP and B3PW91, were used. The overestimations of the calculated harmonic wavenumbers were efficiently corrected by the aid of a specific scaling procedure. This empirical scaling process significantly increased the reliability of our assignments and analyses on the observed bands due to different vibrational normal modes of the molecule. For the majority of the normal modes, the deviations between the corresponding experimental and scaled theoretical wavenumbers have located in the expected range. A correct characterization of the normal modes is of vital importance in the assignment of the observed bands, and this was successfully done by the aid of the Potential Energy Distributions (PEDs) separately calculated for each normal mode of 3,5-DCBN.
The NIR-FT Raman and FT-IR spectral analysis of chloramphenicol, a potential antibacterial drug f... more The NIR-FT Raman and FT-IR spectral analysis of chloramphenicol, a potential antibacterial drug for the treatment of typhoid fever, is carried out along with ab initio computations. Presence of blue-shifting H-bonds, and influence of intra-molecular charge transfer interactions, πelectron delocalization and H-bonding are discussed based on the vibrational spectrum. Chloramphenicol (CLM), now synthesized chemically, but originally isolated from cultures of the bacterium streptomyces venezuelae, achieves its antibacterial effect by interfering with protein synthesis in microorganisms. It is effective against bacteria causing diseases, such as rickettsioses, influenza, meningitis and mycoplasma, but is the preferred treatment only for typhoid fever [1]. As part of recent interest in this compound, studies on its fluorescence mechanism have been reported [2]. The present contribution reports the FT-IR and NIR-FT Raman spectral analysis of the molecule supported by ab initio computations...
Single crystals of (RS)-phenylsuccinic acid (RSPSA) were grown by the slow evaporation technique ... more Single crystals of (RS)-phenylsuccinic acid (RSPSA) were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. The density functional ...
Acemetacin is a non-opioid analgesic which belongs to the class, the non-steroidal anti-inflammat... more Acemetacin is a non-opioid analgesic which belongs to the class, the non-steroidal anti-inflammatory drug. The bioactive conformer was identified through potential energy surface scan studies. Spectral features of acemetacin have been probed by the techniques of Fourier transform infrared, Raman and Nuclear magnetic resonance combined with density functional theory calculations at the B3LYP level with 6-311 þ G(d,p) basis set. The detailed interpretation of vibrational spectral assignments has been carried out on the basis of potential energy distribution method. Geometrical parameters reveal that the carbonyl substitution in between chlorophenyl and indole ring leads to a significant loss of planarity. The red-shifted C]O stretching wavenumber describe the conjugation between N and O atoms. The shifted CeH stretching wavenumbers of OeCH 3 and OeCH 2 groups depict the back-donation and induction effects. The substitution of halogen atoms on the title molecule influences the charge distribution and the geometrical parameters. Drug activity and binding affinity of halogen substitution in title molecule with target protein were undertaken by molecular docking study. This study enlightens the effects of bio-efficiency due to the halogen substitution in the molecule.
L-Histidine Potassium Chloride (LHPC) crystals were grown by slow evaporation technique. The grow... more L-Histidine Potassium Chloride (LHPC) crystals were grown by slow evaporation technique. The grown crystals were characterized by powder X-ray diffraction and analyzed by FT-IR and FT-Raman techniques. The geometry optimization, harmonic vibrational wavenumbers, natural bond orbital and thermodynamical analysis have been carried out using density functional theory (DFT) method at B3LYP/6-311++G(d,p) basis set. Optimized geometry values show a small deviation between the experimental and theoretical values, which reveals the inter-and intra-molecular hydrogen bonding in the crystal. Normal coordinate analysis has been performed on the basis of potential energy distribution analysis using MOLVIB program. The potential energy distribution analysis is useful to predict the vibrational modes, unambiguously. The natural bond orbital analysis has been performed in order to study the intramolecular bonding interactions among bonds and delocalization of unpaired electrons. HOMO and LUMO energies, molecular electrostatic potential and the first-order hyperpolarizability have been also studied. The scaled wavenumbers are in good agreement with the experimental wavenumbers. The first-order hyperpolarizability (β) of the title compound is found to be 9.50x10-30 e.s.u. The large hyperpolarizability and lowering of HOMO-LUMO energy gap supported the nonlinearility of the LHPC crystal. On the basis of vibrational analysis the thermodynamic properties of LHPC at different temperatures have been calculated, revealing the correlations between heat capacity, enthalpy and entropy.
The FT-IR and FT-Raman spectra of 2-amino-5-chlorobenzophenone have been recorded and analyzed. S... more The FT-IR and FT-Raman spectra of 2-amino-5-chlorobenzophenone have been recorded and analyzed. Structural geometry, vibrational wavenumbers and first-order hyperpolarizability were computed using density functional theory method. N-H … O distance shows the possibility of intramolecular hydrogen bonding. Natural bond orbital analysis confirms the presence of the N-H … O hydrogen bonding. The computed first-order hyperpolarizability value suggests that 2-amino-5chlorobenzophenone has a potential for producing the second harmonic generation.
Bioactive molecules are playing essential role in the field of drug discovery and various pharmac... more Bioactive molecules are playing essential role in the field of drug discovery and various pharmaceutical applications. Vibrational spectral investigations of the anti-Candida agent ({[(1E)-3-(1H-imidazol-1-yl)-1-phenylpropylidene]amino}oxy)(4-methylphenyl)methanone ((1E)-IPMM) have been recorded and analyzed to understand its structural geometry, inter-and intra-molecular interactions. The equilibrium geometry, harmonic vibrational wavenumber, natural bond orbital (NBO) and Frontier orbital energy analyses have been carried out with the help of density functional theory with B3LYP/6-311++G(d,p) level of theory. The detailed vibrational assignments for the title molecule were performed on the basis of potential energy distribution analysis in order to unambiguously predict its modes. The calculated wavenumbers had good agreement with the experimental values. NBO analysis has confirmed the intramolecular charge transfer interactions. The predicted docking binding energy gave insight into the possible biological activity of the title molecule.
Heterocyclic Schiff bases are related to first row transition elements is beyond the ambit of our... more Heterocyclic Schiff bases are related to first row transition elements is beyond the ambit of our imagination. However, multidenadate Schiff bases have been widely used as ligands, because they can easily attach to metal ions due to the formation of high stability coordination compounds. Metal complexes of S, N and O containing ligands have attracted considerable attention because of their interesting physico-chemical properties and pounced biological actions. Schiff bases and their
The Fourier Transform Raman and infrared spectra of the crystallized herbicide (2-methylphenoxy)a... more The Fourier Transform Raman and infrared spectra of the crystallized herbicide (2-methylphenoxy)acetic acid (MPA) have been recorded in the region 4000-400 cm À1. The geometry, intermolecular hydrogen bond, and harmonic vibrational frequencies of MPA have been investigated with the help of B3LYP density functional theory (DFT) methods. The calculated molecular geometry has been compared with the experimental data obtained from XRD data. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The strong doubly hydrogen bonded interface of the dimerized system is well demonstrated by the red shift in OH stretching frequency concomitant with the elongation of bond length. The most stable structure of the dimer possesses center of symmetry and interaction energy of À83.642 kJ mol À1 after the basis set superposition error (BSSE) correction by the counterpoise (CP) method. The natural bond orbital analysis (NBO) ascertains that the delocalization of unpaired electron of oxygen atom onto the CO bond causes double bond character.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011
The NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded a... more The NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded and analyzed. Density functional theory (DFT) calculation of two BAC conformers has been performed to find the optimized structures and computed vibrational wavenumbers of the most stable one. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Characteristic vibrational bands of the pyrone ring and methylene and carbonyl groups have been identified. The lowering of HOMO-LUMO energy gap clearly explains the charge transfer interactions taking place within the molecule.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2004
The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational ... more The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational spectral analysis is carried out using NIR-FT Raman and FT-IR spectra. The ab initio quantum computations are also performed at HF/6-31 G(d) level to derive the optimized geometry, atomic charges and vibrational frequencies of the glycinium oxalate molecule. Vibrational analysis indicates the presence of peculiar intermolecular C-H• • • O hydrogen bonding interaction producing 'blue shift' of C-H stretching frequency. The vibrational spectra confirm the existence of NH 3 + in glycinium oxalate. Hydroxyl vibrations with different inter and intra molecular H-bonding are analysed, supported by computed results.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis subs... more The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis substance comprestatin A-4 prodrug (CA4P) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of CA4P have been investigated with the help of B3LYP density functional theory (DFT) method. The most preferred cis-configuration for its bioactivity has been demonstrated on the basis of torsional potential energy surface (PES) scan studies. Stability of the molecule arising from hyperconjugative interactions leading to its bioactivity, charge delocalization and mesomeric effects have been analyzed using natural bond orbital (NBO) analysis. Detailed assignments of the vibrational spectra have been made with the aid of theoretically predicted vibrational frequencies. The optimized geometry shows near-planarity of phenyl rings and perpendicular conformation of meta substituted methoxy group. The vibrational analysis confirms the differently acting ring modes, steric repulsion, pi conjugation and back-donation.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
FT Raman and IR spectra of the crystallized biologically active molecule, L-alanylglycine (L-Ala-... more FT Raman and IR spectra of the crystallized biologically active molecule, L-alanylglycine (L-Ala-Gly) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies of L-Ala-Gly have been investigated with the help of B3LYP density functional theory (DFT) method. The calculated molecular geometry has been compared with the experimental data. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The optimized geometry shows the non-planarity of the peptide group of the molecule. Potential energy surface (PES) scan studies has also been carried out by ab initio calculations with B3LYP/6-311+G** basis set. The red shifting of NH3+ stretching wavenumber indicates the formation of N-H...O hydrogen bonding. The change in electron density (ED) in the sigma* antibonding orbitals and E2 energies have been calculated by natural bond orbital analysis (NBO) using DFT method. The NBO analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
FT-IR and Raman techniques were employed for the vibrational characterization of the food additiv... more FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and pi-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H ...O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.
ABSTRACT The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Fluoro-phenyl)-1H-imidazole ... more ABSTRACT The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Fluoro-phenyl)-1H-imidazole (4-FPI) were recorded and analyzed. Density functional method (B3LYP level with the 6–311G(d, p) and 6–311++G(d, p) and cc-pVQZ as basis sets) has been used to compute optimized geometry, vibrational wavenumbers of the 4-FPI. Only one tautomeric form was found most stable by using DFT/B3LYP. The detailed interpretation of the vibrational spectra was carried out with the aid of total energy distribution following the scaled quantum mechanical force field methodology. Potential Energy Surface scan studies has also been carried out by ab initio calculations with the same basis sets.
Abstract Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporati... more Abstract Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies ...
Amalanathan, M., Hubert Joe, I. and Kostova, I.(2010), Density functional theory calculation and ... more Amalanathan, M., Hubert Joe, I. and Kostova, I.(2010), Density functional theory calculation and vibrational spectral analysis of 4-hydroxy-3-(3-oxo-1-phenylbutyl)-2H-1-benzopyran-2-one. Journal of Raman Spectroscopy, 41: 1076–1084. doi: 10.1002/jrs. 2543
Non-hormonal isoflavone derivative 7-Isopropoxy-3-phenyl-4H-1-benzopyran-4-one (7I3P4H) is used f... more Non-hormonal isoflavone derivative 7-Isopropoxy-3-phenyl-4H-1-benzopyran-4-one (7I3P4H) is used for prevention and treatment of postmenopausal osteoporosis. It is also used for reducing bone loss caused by chronic kidney diseases and paralysis associated with stroke. Optimized geometry and Natural Bond Orbital (NBO) analysis of 7I3P4HB carried out to demonstrate the various intra-molecular interactions that are responsible for the stabilization of this molecule leading to its medicinal activity. Ultraviolet Absorption (UV) spectra have been recorded and analyzed. Energy gap has been calculated from Frontier Molecular Orbital Analysis with the help of B3LYP/6-311++G (d, p) method.
Naphthalene 2-sulfonic acid (NSA) and its derivatives are the most important class of organic com... more Naphthalene 2-sulfonic acid (NSA) and its derivatives are the most important class of organic compounds and are important products of industrial chemical processes.. Bioactive molecule NSA was performed by means of Density Functional Theoretical (DFT) method using standard B3LYP/6-31G (d,p) basis set implemented with Gaussian'09 software package. NBO analysis were performed to provide valuable information about various intermolecular interactions. Optical properties of the NSA molecule were studied using UV-Vis spectral analysis. In addition, Molecular docking was performed for the different receptors for calculating binding affinities and predicting binding sites.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
The IR and Raman spectra of 3,5-dichlorobenzonitrile (3,5-DCBN) molecule were recorded at room te... more The IR and Raman spectra of 3,5-dichlorobenzonitrile (3,5-DCBN) molecule were recorded at room temperature and then the assignment of the observed fundamental bands were achieved by the aid of the theoretical vibrational spectral data obtained from a quantum chemical study carried out for the free molecule case. In the calculations performed to determine the molecular geometry, vibrational spectral data and thermodynamic parameters, Møller-Plesset second order perturbation theory (MP2) and hybrid Density Functional Theory (DFT) types of electronic structure methods, B3LYP and B3PW91, were used. The overestimations of the calculated harmonic wavenumbers were efficiently corrected by the aid of a specific scaling procedure. This empirical scaling process significantly increased the reliability of our assignments and analyses on the observed bands due to different vibrational normal modes of the molecule. For the majority of the normal modes, the deviations between the corresponding experimental and scaled theoretical wavenumbers have located in the expected range. A correct characterization of the normal modes is of vital importance in the assignment of the observed bands, and this was successfully done by the aid of the Potential Energy Distributions (PEDs) separately calculated for each normal mode of 3,5-DCBN.
The NIR-FT Raman and FT-IR spectral analysis of chloramphenicol, a potential antibacterial drug f... more The NIR-FT Raman and FT-IR spectral analysis of chloramphenicol, a potential antibacterial drug for the treatment of typhoid fever, is carried out along with ab initio computations. Presence of blue-shifting H-bonds, and influence of intra-molecular charge transfer interactions, πelectron delocalization and H-bonding are discussed based on the vibrational spectrum. Chloramphenicol (CLM), now synthesized chemically, but originally isolated from cultures of the bacterium streptomyces venezuelae, achieves its antibacterial effect by interfering with protein synthesis in microorganisms. It is effective against bacteria causing diseases, such as rickettsioses, influenza, meningitis and mycoplasma, but is the preferred treatment only for typhoid fever [1]. As part of recent interest in this compound, studies on its fluorescence mechanism have been reported [2]. The present contribution reports the FT-IR and NIR-FT Raman spectral analysis of the molecule supported by ab initio computations...
Single crystals of (RS)-phenylsuccinic acid (RSPSA) were grown by the slow evaporation technique ... more Single crystals of (RS)-phenylsuccinic acid (RSPSA) were grown by the slow evaporation technique and vibrational spectral analysis was carried out using near-IR Fourier transform Raman and Fourier transform IR spectroscopy. The density functional ...
Acemetacin is a non-opioid analgesic which belongs to the class, the non-steroidal anti-inflammat... more Acemetacin is a non-opioid analgesic which belongs to the class, the non-steroidal anti-inflammatory drug. The bioactive conformer was identified through potential energy surface scan studies. Spectral features of acemetacin have been probed by the techniques of Fourier transform infrared, Raman and Nuclear magnetic resonance combined with density functional theory calculations at the B3LYP level with 6-311 þ G(d,p) basis set. The detailed interpretation of vibrational spectral assignments has been carried out on the basis of potential energy distribution method. Geometrical parameters reveal that the carbonyl substitution in between chlorophenyl and indole ring leads to a significant loss of planarity. The red-shifted C]O stretching wavenumber describe the conjugation between N and O atoms. The shifted CeH stretching wavenumbers of OeCH 3 and OeCH 2 groups depict the back-donation and induction effects. The substitution of halogen atoms on the title molecule influences the charge distribution and the geometrical parameters. Drug activity and binding affinity of halogen substitution in title molecule with target protein were undertaken by molecular docking study. This study enlightens the effects of bio-efficiency due to the halogen substitution in the molecule.
L-Histidine Potassium Chloride (LHPC) crystals were grown by slow evaporation technique. The grow... more L-Histidine Potassium Chloride (LHPC) crystals were grown by slow evaporation technique. The grown crystals were characterized by powder X-ray diffraction and analyzed by FT-IR and FT-Raman techniques. The geometry optimization, harmonic vibrational wavenumbers, natural bond orbital and thermodynamical analysis have been carried out using density functional theory (DFT) method at B3LYP/6-311++G(d,p) basis set. Optimized geometry values show a small deviation between the experimental and theoretical values, which reveals the inter-and intra-molecular hydrogen bonding in the crystal. Normal coordinate analysis has been performed on the basis of potential energy distribution analysis using MOLVIB program. The potential energy distribution analysis is useful to predict the vibrational modes, unambiguously. The natural bond orbital analysis has been performed in order to study the intramolecular bonding interactions among bonds and delocalization of unpaired electrons. HOMO and LUMO energies, molecular electrostatic potential and the first-order hyperpolarizability have been also studied. The scaled wavenumbers are in good agreement with the experimental wavenumbers. The first-order hyperpolarizability (β) of the title compound is found to be 9.50x10-30 e.s.u. The large hyperpolarizability and lowering of HOMO-LUMO energy gap supported the nonlinearility of the LHPC crystal. On the basis of vibrational analysis the thermodynamic properties of LHPC at different temperatures have been calculated, revealing the correlations between heat capacity, enthalpy and entropy.
The FT-IR and FT-Raman spectra of 2-amino-5-chlorobenzophenone have been recorded and analyzed. S... more The FT-IR and FT-Raman spectra of 2-amino-5-chlorobenzophenone have been recorded and analyzed. Structural geometry, vibrational wavenumbers and first-order hyperpolarizability were computed using density functional theory method. N-H … O distance shows the possibility of intramolecular hydrogen bonding. Natural bond orbital analysis confirms the presence of the N-H … O hydrogen bonding. The computed first-order hyperpolarizability value suggests that 2-amino-5chlorobenzophenone has a potential for producing the second harmonic generation.
Bioactive molecules are playing essential role in the field of drug discovery and various pharmac... more Bioactive molecules are playing essential role in the field of drug discovery and various pharmaceutical applications. Vibrational spectral investigations of the anti-Candida agent ({[(1E)-3-(1H-imidazol-1-yl)-1-phenylpropylidene]amino}oxy)(4-methylphenyl)methanone ((1E)-IPMM) have been recorded and analyzed to understand its structural geometry, inter-and intra-molecular interactions. The equilibrium geometry, harmonic vibrational wavenumber, natural bond orbital (NBO) and Frontier orbital energy analyses have been carried out with the help of density functional theory with B3LYP/6-311++G(d,p) level of theory. The detailed vibrational assignments for the title molecule were performed on the basis of potential energy distribution analysis in order to unambiguously predict its modes. The calculated wavenumbers had good agreement with the experimental values. NBO analysis has confirmed the intramolecular charge transfer interactions. The predicted docking binding energy gave insight into the possible biological activity of the title molecule.
Heterocyclic Schiff bases are related to first row transition elements is beyond the ambit of our... more Heterocyclic Schiff bases are related to first row transition elements is beyond the ambit of our imagination. However, multidenadate Schiff bases have been widely used as ligands, because they can easily attach to metal ions due to the formation of high stability coordination compounds. Metal complexes of S, N and O containing ligands have attracted considerable attention because of their interesting physico-chemical properties and pounced biological actions. Schiff bases and their
The Fourier Transform Raman and infrared spectra of the crystallized herbicide (2-methylphenoxy)a... more The Fourier Transform Raman and infrared spectra of the crystallized herbicide (2-methylphenoxy)acetic acid (MPA) have been recorded in the region 4000-400 cm À1. The geometry, intermolecular hydrogen bond, and harmonic vibrational frequencies of MPA have been investigated with the help of B3LYP density functional theory (DFT) methods. The calculated molecular geometry has been compared with the experimental data obtained from XRD data. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The strong doubly hydrogen bonded interface of the dimerized system is well demonstrated by the red shift in OH stretching frequency concomitant with the elongation of bond length. The most stable structure of the dimer possesses center of symmetry and interaction energy of À83.642 kJ mol À1 after the basis set superposition error (BSSE) correction by the counterpoise (CP) method. The natural bond orbital analysis (NBO) ascertains that the delocalization of unpaired electron of oxygen atom onto the CO bond causes double bond character.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011
The NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded a... more The NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded and analyzed. Density functional theory (DFT) calculation of two BAC conformers has been performed to find the optimized structures and computed vibrational wavenumbers of the most stable one. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Characteristic vibrational bands of the pyrone ring and methylene and carbonyl groups have been identified. The lowering of HOMO-LUMO energy gap clearly explains the charge transfer interactions taking place within the molecule.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2004
The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational ... more The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational spectral analysis is carried out using NIR-FT Raman and FT-IR spectra. The ab initio quantum computations are also performed at HF/6-31 G(d) level to derive the optimized geometry, atomic charges and vibrational frequencies of the glycinium oxalate molecule. Vibrational analysis indicates the presence of peculiar intermolecular C-H• • • O hydrogen bonding interaction producing 'blue shift' of C-H stretching frequency. The vibrational spectra confirm the existence of NH 3 + in glycinium oxalate. Hydroxyl vibrations with different inter and intra molecular H-bonding are analysed, supported by computed results.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis subs... more The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis substance comprestatin A-4 prodrug (CA4P) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of CA4P have been investigated with the help of B3LYP density functional theory (DFT) method. The most preferred cis-configuration for its bioactivity has been demonstrated on the basis of torsional potential energy surface (PES) scan studies. Stability of the molecule arising from hyperconjugative interactions leading to its bioactivity, charge delocalization and mesomeric effects have been analyzed using natural bond orbital (NBO) analysis. Detailed assignments of the vibrational spectra have been made with the aid of theoretically predicted vibrational frequencies. The optimized geometry shows near-planarity of phenyl rings and perpendicular conformation of meta substituted methoxy group. The vibrational analysis confirms the differently acting ring modes, steric repulsion, pi conjugation and back-donation.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
FT Raman and IR spectra of the crystallized biologically active molecule, L-alanylglycine (L-Ala-... more FT Raman and IR spectra of the crystallized biologically active molecule, L-alanylglycine (L-Ala-Gly) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies of L-Ala-Gly have been investigated with the help of B3LYP density functional theory (DFT) method. The calculated molecular geometry has been compared with the experimental data. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The optimized geometry shows the non-planarity of the peptide group of the molecule. Potential energy surface (PES) scan studies has also been carried out by ab initio calculations with B3LYP/6-311+G** basis set. The red shifting of NH3+ stretching wavenumber indicates the formation of N-H...O hydrogen bonding. The change in electron density (ED) in the sigma* antibonding orbitals and E2 energies have been calculated by natural bond orbital analysis (NBO) using DFT method. The NBO analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2009
FT-IR and Raman techniques were employed for the vibrational characterization of the food additiv... more FT-IR and Raman techniques were employed for the vibrational characterization of the food additive Carmoisine (E122). The equilibrium geometry, various bonding features, and harmonic vibrational wavenumbers have been investigated with the help of density functional theory (DFT) calculations. A good correlation was found between the computed and experimental wavenumbers. Azo stretching wavenumbers have been lowered due to conjugation and pi-electron delocalization. Predicted electronic absorption spectra from TD-DFT calculation have been analysed comparing with the UV-vis spectrum. The first hyperpolarizability of the molecule is calculated. Intramolecular charge transfer (ICT) responsible for the optical nonlinearity of the dye molecule has been discussed theoretically and experimentally. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and C-H ...O, improper, blue shifted hydrogen bonds have been analysed using natural bond orbital (NBO) analysis.
ABSTRACT The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Fluoro-phenyl)-1H-imidazole ... more ABSTRACT The FT-IR, FT-Raman and FT-NMR spectra of the compound 4-(4-Fluoro-phenyl)-1H-imidazole (4-FPI) were recorded and analyzed. Density functional method (B3LYP level with the 6–311G(d, p) and 6–311++G(d, p) and cc-pVQZ as basis sets) has been used to compute optimized geometry, vibrational wavenumbers of the 4-FPI. Only one tautomeric form was found most stable by using DFT/B3LYP. The detailed interpretation of the vibrational spectra was carried out with the aid of total energy distribution following the scaled quantum mechanical force field methodology. Potential Energy Surface scan studies has also been carried out by ab initio calculations with the same basis sets.
Abstract Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporati... more Abstract Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies ...
Amalanathan, M., Hubert Joe, I. and Kostova, I.(2010), Density functional theory calculation and ... more Amalanathan, M., Hubert Joe, I. and Kostova, I.(2010), Density functional theory calculation and vibrational spectral analysis of 4-hydroxy-3-(3-oxo-1-phenylbutyl)-2H-1-benzopyran-2-one. Journal of Raman Spectroscopy, 41: 1076–1084. doi: 10.1002/jrs. 2543
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