Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014
FT-IR and FT-Raman spectra of anethole (1-Methoxy-4-(1-propenyl)benzene), a flavoring agent of co... more FT-IR and FT-Raman spectra of anethole (1-Methoxy-4-(1-propenyl)benzene), a flavoring agent of commercial value, have been recorded in the regions 4000-400 and 4000-100cm(-1) respectively. The structure of the title molecule has been optimized and the structural parameters have been calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers as well as their intensities were calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. UV-Vis spectrum of the title compound was recorded in the region 200-500nm and the electronic properties such as HOMO and LUMO energies and associated energy gap were calculated by Time dependent-density functional theory (TD-DFT) approach. Nonlinear optical (NLO) study divulges the nonlinear properties of the molecule. Stability of the title molecule arising from hyper-conjugative interactions and charge delocalization has been investigated using natural bond orbital (NBO) analysis. The theoretical results were found to be in coherence with the measured experimental data.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014
Molecular geometry and vibrational wavenumbers of 2(3H)-Benzothiazolone (C7H5NSO, HBT) was invest... more Molecular geometry and vibrational wavenumbers of 2(3H)-Benzothiazolone (C7H5NSO, HBT) was investigated using density functional (DFT/B3LYP) method with 6-311+G(d,p) basis set. The vibrational wavenumbers are found to be in good agreement with experimental FT-IR spectra. Hydrogen-bonded dimer of HBT, optimized by counterpoise correction, was studied by MP2 and DFT/B3LYP at the 6-311+G(d,p) level and the effects of molecular association through NH---O hydrogen bonding were discussed. A detailed analysis of the nature of the hydrogen bonding, using topological parameters, such as electronic charge density, Laplacian, kinetic and potential energy density evaluated at bond critical points (BCP) has also been presented. The UV absorption spectra of the compound dissolved in ethanol and chloroform solutions were recorded in the range of 200-600 nm. The UV-vis spectrum of the title molecule was also calculated using TD-DFT method. The calculated energy and oscillator strength almost exactly reproduce the experimental data. Total and partial density of state (TDOS, PDOS) of the HBT in terms of HOMOs and LUMOs and molecular electrostatic potential (MEP) were calculated and analyzed. The electric dipole moment, polarizability and the first static hyper-polarizability values for HBT were calculated at the DFT/B3LYP with 6-311+G(d,p) basis set. The results also show that the HBT molecule may have nonlinear optical (NLO) comportment with non-zero values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization was analyzed using natural bond orbital (NBO) analysis.
In the present communication, we report molecular interaction studies in binary systems of N,N-di... more In the present communication, we report molecular interaction studies in binary systems of N,N-dimethylacetamide (DMA) with 1-propanol and methanol. The density (ρm) and ultrasonic velocity (um) have been measured experimentally for binary solutions of DMA with 1-propanol and methanol at varying concentrations and temperatures. The intermolecular interactions present in the mixtures have been investigated through deviation in ultrasonic velocity (Δu), excess acoustic impedance (ZE), and excess intermolecular free length (LfE). Various semi-empirical mixing rules and theories were proposed by Nomoto, Vandeal, Junjie, collision factor theory (CFT), and Flory’s statistical theory (FST) to estimate the ultrasonic velocity of liquid mixtures. Hankinson-Brobst-Thomson (HBT) and Rackett density models have been used to compare the experimental and theoretically calculated density values. The experimental data are in good agreement with the calculated data as obtained by the DFT (B3LYP and CAM-B3LYP) method.
The molecular geometry and vibrational frequencies of Lantadene A in the ground state have been c... more The molecular geometry and vibrational frequencies of Lantadene A in the ground state have been calculated by Semi-empirical AM1 and PM3 parametrizations. Semi-empirical methods can produce reasonable results on relatively large molecules (near 100s of atoms) in a reasonable amount of time. The experimental frequencies of Lantadene A and the frequencies calculated by AM1 and PM3 methods are nearly the same. Quantum chemical calculations have been carried out to understand the dynamical behaviour of the bioactive molecule Lantadene A.
Present work deals with the quantum mechanical study of the molecular structure of two wellknown ... more Present work deals with the quantum mechanical study of the molecular structure of two wellknown voltage sensitive potassium channel blockers: 4, Aminopyridine and 3, 4 Diaminopyridine. The equilibrium geometry, harmonic vibrational frequencies and HOMO-LUMO gap have been calculated by the density functional theory (DFT), employing 6-311++G (2d, 2p) as the basis set. A detailed interpretation of the infrared and Raman spectra of 4, aminopyridine and 3, 4 Diaminopyridine in terms of the potential energy distribution (P.E.D) is reported. The similarities and differences between the vibrational spectra of the two molecules studied have been highlighted. The thermodynamic calculations related to the title compounds were also performed at B3LYP/6-311++G (2d, 2p) level of theory.
A comprehensive investigation of the ground state structural, spectral and electronic properties ... more A comprehensive investigation of the ground state structural, spectral and electronic properties of Pyridine and Pentachloropyridine (PCP) have been performed using B3LYP/6-311++G (d,p) level of theory. The complete vibrational assignment and analysis of the fundamental modes of both molecules were carried out using theoretical and experimental FTIR spectral data. The effect of substitution of electronegative chlorine atoms at the Pyridine ring, on the structural, vibrational and other properties has been analyzed and discussed. The frontier molecular orbitals analysis and molecular electrostatic potential surface (MESP) map have also been calculated to get a better insight of the properties of the title molecules. The mean polarizability of PCP is found to be 3.66 times more than Pyridine, whereas the dipole moment for Pyridine and PCP are calculated to be 2.3654 and 1.5262 Debye respectively.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2015
Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-am... more Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-aminopyridine compound by means of experimental and computational methods. To achieve this, three-dimensional potential energy scan (PES) was performed by varying the selected dihedral angles at B3LYP/6-31+G(d,p) level of theory and thus stable conformers of the title compound were determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Experimentally, vibrational features of title compound were determined by FT-IR and FT-Raman spectroscopic methods in the solid phase while the electronic absorption spectrum was recorded in methanol solution. On the basis of these investigations, the conformational and spectroscopic attributes of 2-acetamido-5-aminopyridine were interpreted.
Abstract Ultrasonic velocity measurements along with derived parameters provide an important info... more Abstract Ultrasonic velocity measurements along with derived parameters provide an important information regarding the nature of miscibility and molecular interactions in polymeric solutions. Experimental measurements on ultrasonic velocity (u), density (ρ), refractive index (n) and viscosity (η) have been made for poly(vinylpyrrolidone) (PVP) with ethanol, 1-propanol, and 1-butanol at varying concentrations ranging from (0.1% to 0.9%) and temperatures (283.15 K to 303.15 K). Thermo-physical parameters viz. intermolecular free length (Lf) and adiabatic compressibility (βα) have been evaluated from the experimental data. On the basis of the variation of these parameters with concentration, the nature of polymer-solvent interaction has been studied which indicates the existence of molecular interaction between the polymer and the alcohols. FT-IR spectrum of pure PVP and their solutions and optical absorption spectra at concentrations (0.3%, 0.4%, 0.5%, 0.6%) have been recorded in the wavenumber range (4000–500 cm−1) and wavelength range (200–400 nm) respectively. The optical band gap has been calculated for PVP solutions. The experimental data are in good agreement with the calculated data as obtained by the DFT/B3LYP method.
ABSTRACT Detailed structural, electronic and spectroscopic study of 4-methylthiadiazole-5-carboxy... more ABSTRACT Detailed structural, electronic and spectroscopic study of 4-methylthiadiazole-5-carboxylic acid, one of the simplest 1,2,3-thiadiazole derivatives has been performed using density functional theory at four different functionals (B3LYP, X3LYP, CAM-B3LYP and M06-2X). The two possible conformers and their dimeric forms have been investigated for the stability and hence for the calculation of molecular properties of the title compound. Vibrational analysis has been performed with the help of experimental FT-IR and FT-Raman spectra. NBO analysis has been performed to estimate the N–H—O=C hydrogen bond strength and to evaluate the intra and inter molecular charge transfer in the system. Intermolecular hydrogen-bond strength has also been computed using Atoms in Molecules (AIM) theory. To visualise spatial domain, key sites of electron transitions and electron density difference between ground as well as excited states, and their 2D and 3D plots have been computed. Solvent effect on the intermolecular hydrogen bonding have also been investigated using solvents of different polarities. Non-linear optical properties, molecular electrostatic potential surface map (MESP), thermodynamic potentials at different temperatures have also been computed and plotted.
Abstract The FT-Raman and FT-IR spectra of N -(adamantan-1-yl)-1,2,3,4-tetrahydroisoquinoline-2-c... more Abstract The FT-Raman and FT-IR spectra of N -(adamantan-1-yl)-1,2,3,4-tetrahydroisoquinoline-2-carbothioamide were recorded and investigated. The DFT/M06-2X/6-311++G(d,p) method was used to compute the vibrational wavenumbers. The effect of solvents (water, carbon tetrachloride and chloroform) on the dipole moment and polarizability has been evaluated. UV–Vis spectrum of the title compound was recorded and compared with the theoretical spectrum calculated by TD-DFT approach. To investigate the movement of electrons within the system when excited, the difference of the excited and ground state densities has also been plotted. The molecular docking studies reveals that the investigated compound may exhibit HIV-1 Protease inhibitory activity.
Abstract Investigation of ground state geometry, molecular properties and electronic structure of... more Abstract Investigation of ground state geometry, molecular properties and electronic structure of methyl 1H-indol-5-carboxylate has been reported for the first time using the implements of density functional theory. The two possible conformers of the title compound were first optimized at B3LYP/6-31G(d) and then further at B3LYP, M06-2X and CAM-B3LYP functionals at 6-311++G(d,p) basis set. A comprehensive vibrational analysis has been performed for both the conformers at B3LYP/6-311++G(d,p). Good agreement between theoretical spectral data with experimental spectra has been obtained. Polarizability and first static hyperpolarizability have been compared at different functionals used in the present study. To estimate the intra-molecular delocalization along with the inter-molecular interaction, the NBO analysis has been done for monomer and dimer of the title molecule. Topological parameters at the bond critical point involved in intermolecular hydrogen-bonding have also been calculated using AIM theory to assess the strength of hydrogen bonding. Effects of solvents (water, carbon tetrachloride and chloroform) on the optimized geometry and the inter-molecular hydrogen bonding have been evaluated. UV–Vis spectrum of the title compound was also recorded and electronic properties such as frontier orbitals and their corresponding energy gap have also been calculated by TD-DFT approach.
Abstract Quantum chemical calculations of geometrical structure, energy and vibrational wavenumbe... more Abstract Quantum chemical calculations of geometrical structure, energy and vibrational wavenumbers of a novel functionalized pyrido-pyrimidine compound (a prospective antibacterial agent), chemically known as 6-Methyl,13,14,15-Trihydro-14-(4-Nitrophenyl)pyrido[1,2-a:1′,2′-a′] pyrido[2″,3″-d:6″,5″-d′]dipyrimidine-13,15-dione (C 24 H 16 N 6 O 4 ), were carried out, using B3LYP/6311++G(d,p) method. Comprehensive interpretation of the infrared and Raman spectra of the compound under study is based on potential energy distribution. A good coherence between experimental and theoretical wavenumbers shows the preciseness of the assignments. NLO properties like the dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface have been calculated to get a better cognizance of the properties of the title compound. Molecular docking results reveal that the title compound exhibit inhibitory activity against Staphylococcus aureus .
Abstract In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyri... more Abstract In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyridinedicarboxylic acid), in zwitterionic and neutral forms, were presented using FT-IR, FT-Raman, NMR, UV experimental techniques and quantum chemical calculations. FT-IR and FT-Raman spectra of 2,3-pyridinedicarboxylic acid (2,3-PDCA) in the solid phase were recorded in the region 4000–400 cm −1 and 3500–0 cm −1 , respectively. The geometrical parameters and energies were obtained for zwitter and neutral forms by using density functional theory (DFT) at B3LYP/6-311++G(d,p) level of theory. 3D potential energy scan was performed by varying the selected dihedral angles using M06-2X and B3LYP functionals at 6-31G(d) level of theory and thus the most stable conformer of the title compound was determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Theoretical vibrational assignment of 2,3-PDCA, using percentage potential energy distribution (PED) was done with MOLVIB program. 13 C and 1 H NMR spectra were recorded in DMSO. Chemical shifts were calculated at the same level of theory. The UV absorption spectra of the studied compound in ethanol and water were recorded in the range of 200–400 nm. The optimized geometric parameters were compared with experimental data.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 15, 2015
Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-am... more Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-aminopyridine compound by means of experimental and computational methods. To achieve this, three-dimensional potential energy scan (PES) was performed by varying the selected dihedral angles at B3LYP/6-31+G(d,p) level of theory and thus stable conformers of the title compound were determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Experimentally, vibrational features of title compound were determined by FT-IR and FT-Raman spectroscopic methods in the solid phase while the electronic absorption spectrum was recorded in methanol solution. On the basis of these investigations, the conformational and spectroscopic attributes of 2-acetamido-5-aminopyridine were interpreted.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014
FT-IR and FT-Raman spectra of anethole (1-Methoxy-4-(1-propenyl)benzene), a flavoring agent of co... more FT-IR and FT-Raman spectra of anethole (1-Methoxy-4-(1-propenyl)benzene), a flavoring agent of commercial value, have been recorded in the regions 4000-400 and 4000-100cm(-1) respectively. The structure of the title molecule has been optimized and the structural parameters have been calculated by DFT/B3LYP method with 6-311++G(d,p) basis set. The fundamental vibrational wavenumbers as well as their intensities were calculated and a good agreement between observed and scaled calculated wavenumbers has been achieved. UV-Vis spectrum of the title compound was recorded in the region 200-500nm and the electronic properties such as HOMO and LUMO energies and associated energy gap were calculated by Time dependent-density functional theory (TD-DFT) approach. Nonlinear optical (NLO) study divulges the nonlinear properties of the molecule. Stability of the title molecule arising from hyper-conjugative interactions and charge delocalization has been investigated using natural bond orbital (NBO) analysis. The theoretical results were found to be in coherence with the measured experimental data.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014
Molecular geometry and vibrational wavenumbers of 2(3H)-Benzothiazolone (C7H5NSO, HBT) was invest... more Molecular geometry and vibrational wavenumbers of 2(3H)-Benzothiazolone (C7H5NSO, HBT) was investigated using density functional (DFT/B3LYP) method with 6-311+G(d,p) basis set. The vibrational wavenumbers are found to be in good agreement with experimental FT-IR spectra. Hydrogen-bonded dimer of HBT, optimized by counterpoise correction, was studied by MP2 and DFT/B3LYP at the 6-311+G(d,p) level and the effects of molecular association through NH---O hydrogen bonding were discussed. A detailed analysis of the nature of the hydrogen bonding, using topological parameters, such as electronic charge density, Laplacian, kinetic and potential energy density evaluated at bond critical points (BCP) has also been presented. The UV absorption spectra of the compound dissolved in ethanol and chloroform solutions were recorded in the range of 200-600 nm. The UV-vis spectrum of the title molecule was also calculated using TD-DFT method. The calculated energy and oscillator strength almost exactly reproduce the experimental data. Total and partial density of state (TDOS, PDOS) of the HBT in terms of HOMOs and LUMOs and molecular electrostatic potential (MEP) were calculated and analyzed. The electric dipole moment, polarizability and the first static hyper-polarizability values for HBT were calculated at the DFT/B3LYP with 6-311+G(d,p) basis set. The results also show that the HBT molecule may have nonlinear optical (NLO) comportment with non-zero values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization was analyzed using natural bond orbital (NBO) analysis.
In the present communication, we report molecular interaction studies in binary systems of N,N-di... more In the present communication, we report molecular interaction studies in binary systems of N,N-dimethylacetamide (DMA) with 1-propanol and methanol. The density (ρm) and ultrasonic velocity (um) have been measured experimentally for binary solutions of DMA with 1-propanol and methanol at varying concentrations and temperatures. The intermolecular interactions present in the mixtures have been investigated through deviation in ultrasonic velocity (Δu), excess acoustic impedance (ZE), and excess intermolecular free length (LfE). Various semi-empirical mixing rules and theories were proposed by Nomoto, Vandeal, Junjie, collision factor theory (CFT), and Flory’s statistical theory (FST) to estimate the ultrasonic velocity of liquid mixtures. Hankinson-Brobst-Thomson (HBT) and Rackett density models have been used to compare the experimental and theoretically calculated density values. The experimental data are in good agreement with the calculated data as obtained by the DFT (B3LYP and CAM-B3LYP) method.
The molecular geometry and vibrational frequencies of Lantadene A in the ground state have been c... more The molecular geometry and vibrational frequencies of Lantadene A in the ground state have been calculated by Semi-empirical AM1 and PM3 parametrizations. Semi-empirical methods can produce reasonable results on relatively large molecules (near 100s of atoms) in a reasonable amount of time. The experimental frequencies of Lantadene A and the frequencies calculated by AM1 and PM3 methods are nearly the same. Quantum chemical calculations have been carried out to understand the dynamical behaviour of the bioactive molecule Lantadene A.
Present work deals with the quantum mechanical study of the molecular structure of two wellknown ... more Present work deals with the quantum mechanical study of the molecular structure of two wellknown voltage sensitive potassium channel blockers: 4, Aminopyridine and 3, 4 Diaminopyridine. The equilibrium geometry, harmonic vibrational frequencies and HOMO-LUMO gap have been calculated by the density functional theory (DFT), employing 6-311++G (2d, 2p) as the basis set. A detailed interpretation of the infrared and Raman spectra of 4, aminopyridine and 3, 4 Diaminopyridine in terms of the potential energy distribution (P.E.D) is reported. The similarities and differences between the vibrational spectra of the two molecules studied have been highlighted. The thermodynamic calculations related to the title compounds were also performed at B3LYP/6-311++G (2d, 2p) level of theory.
A comprehensive investigation of the ground state structural, spectral and electronic properties ... more A comprehensive investigation of the ground state structural, spectral and electronic properties of Pyridine and Pentachloropyridine (PCP) have been performed using B3LYP/6-311++G (d,p) level of theory. The complete vibrational assignment and analysis of the fundamental modes of both molecules were carried out using theoretical and experimental FTIR spectral data. The effect of substitution of electronegative chlorine atoms at the Pyridine ring, on the structural, vibrational and other properties has been analyzed and discussed. The frontier molecular orbitals analysis and molecular electrostatic potential surface (MESP) map have also been calculated to get a better insight of the properties of the title molecules. The mean polarizability of PCP is found to be 3.66 times more than Pyridine, whereas the dipole moment for Pyridine and PCP are calculated to be 2.3654 and 1.5262 Debye respectively.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2015
Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-am... more Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-aminopyridine compound by means of experimental and computational methods. To achieve this, three-dimensional potential energy scan (PES) was performed by varying the selected dihedral angles at B3LYP/6-31+G(d,p) level of theory and thus stable conformers of the title compound were determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Experimentally, vibrational features of title compound were determined by FT-IR and FT-Raman spectroscopic methods in the solid phase while the electronic absorption spectrum was recorded in methanol solution. On the basis of these investigations, the conformational and spectroscopic attributes of 2-acetamido-5-aminopyridine were interpreted.
Abstract Ultrasonic velocity measurements along with derived parameters provide an important info... more Abstract Ultrasonic velocity measurements along with derived parameters provide an important information regarding the nature of miscibility and molecular interactions in polymeric solutions. Experimental measurements on ultrasonic velocity (u), density (ρ), refractive index (n) and viscosity (η) have been made for poly(vinylpyrrolidone) (PVP) with ethanol, 1-propanol, and 1-butanol at varying concentrations ranging from (0.1% to 0.9%) and temperatures (283.15 K to 303.15 K). Thermo-physical parameters viz. intermolecular free length (Lf) and adiabatic compressibility (βα) have been evaluated from the experimental data. On the basis of the variation of these parameters with concentration, the nature of polymer-solvent interaction has been studied which indicates the existence of molecular interaction between the polymer and the alcohols. FT-IR spectrum of pure PVP and their solutions and optical absorption spectra at concentrations (0.3%, 0.4%, 0.5%, 0.6%) have been recorded in the wavenumber range (4000–500 cm−1) and wavelength range (200–400 nm) respectively. The optical band gap has been calculated for PVP solutions. The experimental data are in good agreement with the calculated data as obtained by the DFT/B3LYP method.
ABSTRACT Detailed structural, electronic and spectroscopic study of 4-methylthiadiazole-5-carboxy... more ABSTRACT Detailed structural, electronic and spectroscopic study of 4-methylthiadiazole-5-carboxylic acid, one of the simplest 1,2,3-thiadiazole derivatives has been performed using density functional theory at four different functionals (B3LYP, X3LYP, CAM-B3LYP and M06-2X). The two possible conformers and their dimeric forms have been investigated for the stability and hence for the calculation of molecular properties of the title compound. Vibrational analysis has been performed with the help of experimental FT-IR and FT-Raman spectra. NBO analysis has been performed to estimate the N–H—O=C hydrogen bond strength and to evaluate the intra and inter molecular charge transfer in the system. Intermolecular hydrogen-bond strength has also been computed using Atoms in Molecules (AIM) theory. To visualise spatial domain, key sites of electron transitions and electron density difference between ground as well as excited states, and their 2D and 3D plots have been computed. Solvent effect on the intermolecular hydrogen bonding have also been investigated using solvents of different polarities. Non-linear optical properties, molecular electrostatic potential surface map (MESP), thermodynamic potentials at different temperatures have also been computed and plotted.
Abstract The FT-Raman and FT-IR spectra of N -(adamantan-1-yl)-1,2,3,4-tetrahydroisoquinoline-2-c... more Abstract The FT-Raman and FT-IR spectra of N -(adamantan-1-yl)-1,2,3,4-tetrahydroisoquinoline-2-carbothioamide were recorded and investigated. The DFT/M06-2X/6-311++G(d,p) method was used to compute the vibrational wavenumbers. The effect of solvents (water, carbon tetrachloride and chloroform) on the dipole moment and polarizability has been evaluated. UV–Vis spectrum of the title compound was recorded and compared with the theoretical spectrum calculated by TD-DFT approach. To investigate the movement of electrons within the system when excited, the difference of the excited and ground state densities has also been plotted. The molecular docking studies reveals that the investigated compound may exhibit HIV-1 Protease inhibitory activity.
Abstract Investigation of ground state geometry, molecular properties and electronic structure of... more Abstract Investigation of ground state geometry, molecular properties and electronic structure of methyl 1H-indol-5-carboxylate has been reported for the first time using the implements of density functional theory. The two possible conformers of the title compound were first optimized at B3LYP/6-31G(d) and then further at B3LYP, M06-2X and CAM-B3LYP functionals at 6-311++G(d,p) basis set. A comprehensive vibrational analysis has been performed for both the conformers at B3LYP/6-311++G(d,p). Good agreement between theoretical spectral data with experimental spectra has been obtained. Polarizability and first static hyperpolarizability have been compared at different functionals used in the present study. To estimate the intra-molecular delocalization along with the inter-molecular interaction, the NBO analysis has been done for monomer and dimer of the title molecule. Topological parameters at the bond critical point involved in intermolecular hydrogen-bonding have also been calculated using AIM theory to assess the strength of hydrogen bonding. Effects of solvents (water, carbon tetrachloride and chloroform) on the optimized geometry and the inter-molecular hydrogen bonding have been evaluated. UV–Vis spectrum of the title compound was also recorded and electronic properties such as frontier orbitals and their corresponding energy gap have also been calculated by TD-DFT approach.
Abstract Quantum chemical calculations of geometrical structure, energy and vibrational wavenumbe... more Abstract Quantum chemical calculations of geometrical structure, energy and vibrational wavenumbers of a novel functionalized pyrido-pyrimidine compound (a prospective antibacterial agent), chemically known as 6-Methyl,13,14,15-Trihydro-14-(4-Nitrophenyl)pyrido[1,2-a:1′,2′-a′] pyrido[2″,3″-d:6″,5″-d′]dipyrimidine-13,15-dione (C 24 H 16 N 6 O 4 ), were carried out, using B3LYP/6311++G(d,p) method. Comprehensive interpretation of the infrared and Raman spectra of the compound under study is based on potential energy distribution. A good coherence between experimental and theoretical wavenumbers shows the preciseness of the assignments. NLO properties like the dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface have been calculated to get a better cognizance of the properties of the title compound. Molecular docking results reveal that the title compound exhibit inhibitory activity against Staphylococcus aureus .
Abstract In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyri... more Abstract In this study, molecular structure and vibrational analysis of quinolinic acid (2,3-pyridinedicarboxylic acid), in zwitterionic and neutral forms, were presented using FT-IR, FT-Raman, NMR, UV experimental techniques and quantum chemical calculations. FT-IR and FT-Raman spectra of 2,3-pyridinedicarboxylic acid (2,3-PDCA) in the solid phase were recorded in the region 4000–400 cm −1 and 3500–0 cm −1 , respectively. The geometrical parameters and energies were obtained for zwitter and neutral forms by using density functional theory (DFT) at B3LYP/6-311++G(d,p) level of theory. 3D potential energy scan was performed by varying the selected dihedral angles using M06-2X and B3LYP functionals at 6-31G(d) level of theory and thus the most stable conformer of the title compound was determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Theoretical vibrational assignment of 2,3-PDCA, using percentage potential energy distribution (PED) was done with MOLVIB program. 13 C and 1 H NMR spectra were recorded in DMSO. Chemical shifts were calculated at the same level of theory. The UV absorption spectra of the studied compound in ethanol and water were recorded in the range of 200–400 nm. The optimized geometric parameters were compared with experimental data.
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 15, 2015
Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-am... more Present work aims at identifying the conformational and spectroscopic profile of 2-acetamido-5-aminopyridine compound by means of experimental and computational methods. To achieve this, three-dimensional potential energy scan (PES) was performed by varying the selected dihedral angles at B3LYP/6-31+G(d,p) level of theory and thus stable conformers of the title compound were determined. The most stable conformer was further optimized at higher level and vibrational wavenumbers were calculated. Experimentally, vibrational features of title compound were determined by FT-IR and FT-Raman spectroscopic methods in the solid phase while the electronic absorption spectrum was recorded in methanol solution. On the basis of these investigations, the conformational and spectroscopic attributes of 2-acetamido-5-aminopyridine were interpreted.
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