Theoretical and vibrational spectral investigation of sodium salt of acenocoumarol

The FT‐IR and FT‐Raman spectra of sodium salt of 4‐hydroxy‐3[1‐(4‐nitrophenyl)‐3‐oxobutyl]‐2H‐1‐benzopyran‐2‐one (acenocoumarol sodium salt) in solid phase have been recorded and analyzed. The optimization geometry, intramolecular hydrogen bonding, and harmonic vibrational wavenumbers of acenocoumarol sodium salt have been investigated with the help of B3LYP density functional theory (DFT) methods. The infrared and Raman spectra were predicted theoretically from the calculated intensities. Natural bond orbital (NBO) analysis indicates the presence of C H···O hydrogen bonding in the molecule. The first static hyperpolarizability of the molecule has been computed. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopic investigations and computational study of 2‐[acetyl(4‐bromophenyl)carbamoyl]‐4‐chlorophenyl acetate

The Fourier transform Raman (FT‐Raman) and Fourier transform infrared (FT‐IR) spectra of 2‐[acetyl(4‐bromophenyl)carbamoyl]‐4‐chlorophenyl acetate were studied. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes, and the normal modes were assigned by potential energy distribution (PED) calculations. The simultaneous Raman and infrared (IR) activations of the CO stretching mode in the carbamoyl moiety show a charge transfer interaction through a π‐conjugated path. From the optimized structure, it is clear that the hydrogen bonding decreases the double bond character of the CO bond and increases the double bond character of the C N bonds. The first hyperpolarizability and predicted IR intensities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar structures, which makes this compound an attractive object for future studies of nonlinear optics. Optimized geometrical parameters of the compound are in agreement with similar reported structures. Copyright © 2009 John Wiley & Sons, Ltd.     

Molecular structure,spectroscopic (FTIR,FTIR gas phase,FT‐Raman) first‐order hyperpolarizability and HOMO–LUMO analysis of 4‐methoxy‐2‐methyl benzoic acid

Vibrational spectral analysis was carried out for 4‐methoxy‐2‐methyl benzoic acid (4M2MBA) by using Fourier transform infrared (FT‐IR) (solid, gas phase) and FT‐Raman spectroscopy in the range of 400–4000 and 10–3500 cm⁻¹ respectively. The effects of molecular association through O H···O hydrogen bonding have been described by the single dimer structure. The theoretical computational density functional theory (DFT) and Hatree‐Fock (HF) method were performed at 6–311++G(d,p) levels to derive the equilibrium geometry, vibrational wavenumbers, infrared intensities and Raman scattering activities. The scaled theoretical wavenumbers were also shown to be in good agreement with experimental data. The first‐order hyperpolarizability (β₀) of this novel molecular system and related properties (β, α₀ and Δα) of 4M2MBA are calculated using the B3LYP/cc‐pvdz basis set, based on the finite‐field approach. A detailed interpretation of the infrared and Raman spectra of 4M2MBA is reported. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule were also constructed and compared with the experimental one. Copyright © 2010 John Wiley & Sons, Ltd.     

FT‐IR,FT‐Raman and DFT calculations of the salicylanilide derivate 4‐chloro‐2‐(4‐bromophenylcarbamoyl)phenyl acetate

FT‐IR and FT‐Raman spectra of 4‐chloro‐2‐(4‐bromophenylcarbamoyl)phenyl acetate were recorded and analyzed. The vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes. The red shift of the NH stretching wavenumber in the infrared (IR) spectrum from the computed wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighbouring oxygen atom. The simultaneous IR and Raman activations of the CO stretching mode give the charge transfer interaction through a π‐conjugated path. Optimized geometrical parameters of the title compound are in agreement with similar reported structures. From the optimized structure, it is clear that the hydrogen bonding decreases the double bond character of CO bond and increases the double bond character of the C N bonds. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non‐linear optics. The assignments of the normal modes are done by potential energy distribution (PED) calculations. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Raman spectroscopic investigation of a new self‐assembly monolayer material 4‐[N‐phenyl‐N‐(3‐methylphenyl)‐amino]‐benzoic acid for organic light‐emitting devices

We have synthesized 4‐[N‐phenyl‐N‐(3‐methylphenyl)‐amino]‐benzoic acid (4‐[PBA]) and investigated its molecular vibrations by infrared and Raman spectroscopies as well as by calculations based on the density functional theory (DFT) approach. The Fourier transform (FT) Raman, dispersive Raman and FT‐IR spectra of 4‐[PBA] were recorded in the solid phase. We analyzed the optimized geometric structure and energies of 4‐[PBA] in the ground state. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital analysis. The results show that change in electron density in the σ* and π* antibonding orbitals and E₂ energies confirm the occurrence of intramolecular charge transfer within the molecule. Theoretical calculations were performed at the DFT level using the Gaussian 09 program. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution. The good agreement between the experimental and theoretical spectra allowed positive assignment of the observed vibrational absorption bands. Finally, the calculation results were applied to simulate the Raman and IR spectra of the title compound, which show agreement with the observed spectra. Copyright © 2011 John Wiley & Sons, Ltd.     

Density functional theory calculation and vibrational spectral analysis of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one

The Fourier transform infrared (4000–400 cm⁻¹) and Fourier transform Raman (3500–500 cm⁻¹) spectra of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one (Warfarin) have been measured and calculated. The structure optimization has been made using density functional theory (DFT) calculations. Complete vibrational assignments of the observed spectra have been compared with theoretical wavenumbers. The wavenumber increasing in the methyl group shows the electronic hyperconjugation effect. The natural bond orbital (NBO) analysis reveals the hyperconjugation interaction and the intramolecular hydrogen bonding. The first‐order hyperpolarizability has been calculated. Copyright © 2009 John Wiley & Sons, Ltd.     

Electron–phonon coupling and vibrational modes contributing to linear electro‐optic effect of the efficient NLO chromophore 4‐(N,N‐dimethylamino)‐N‐methyl‐4′‐toluene sulfonate (DAST) from their vibrational spectra

The optimized geometry and structural features of the most prospective electro‐optic crystal 4‐(N,N‐dimethylamino)‐N‐methyl‐4′‐toluene sulfonate (DAST), and the vibrational spectral investigations have been comprehensively described with the near infrared Fourier transform (NIR FT) Raman and Fourier transform infrared (FT‐IR) spectra supported by the density functional theoretical (DFT) computations to elucidate the contribution of vibrational modes to the linear electro‐optic (LEO) effect. Mulliken population analysis and natural bond orbital (NBO) analysis have also been carried out to analyze the effects of intramolecular charge transfer (ICT), intramolecular hydrogen bonding and hyperconjugative interactions on the geometries. The influence of CT interaction between the phenyl ring and the dimethylamino group of the nonlinear optical (NLO) chromophore on the endocyclic and exocyclic angles, and the electronic effects such as hyperconjugation and back‐donation on the methyl hydrogen atoms have been examined. The concurrent intense activation of Raman and IR activities of the effective conjugation vibrational coordinate, which significantly contributes to the LEO effect resulting from the strong electron–phonon (e/ph) coupling, has been analyzed in detail. The effects of frontier orbitals, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), transition of electron density (ED) transfer and the influence of planarity in the stilbazolium ring on the first hyperpolarizability are also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Electronic and structural effects on the nonlinear optical behavior in π‐conjugated structure bis(4‐nitrophenyl) carbonate: a vibrational spectroscopic approach

Fourier transform (FT)‐Raman and infrared (IR) spectra of the nonlinear optical (NLO) material bis(4‐nitrophenyl) carbonate were recorded and analyzed. The geometry, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of Becke3–Lee–Yang–Parr density functional theory method. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. The second‐order NLO properties of the molecule were studied by the Kurtz and Perry powder reflection technique. Stability of the molecule arising from hyperconjugative interactions leading to its NLO activity and charge delocalization were analyzed using natural bond orbital analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of structure and vibrational spectra of 2,5‐dihydroxybenzoicacid based on density functional theory calculations

The spectra of 2,5‐dihydroxybenzoic acid (DHBA) have been recorded using Fourier transform‐infrared spectroscopy (FT‐IR) and FT‐Raman measurements. The total energy calculations of DHBA were evaluated for various possible conformers. The spectra were interpreted with the help of normal coordinate analysis based on density functional theory (DFT) using standard B3LYP/6–31G* method for the most optimized geometry. The effect of intramolecular hydrogen bonding was discussed. Normal coordinate calculations were performed with the DFT force field corrected by a recommended set of scaling factors, yielding fairly good agreement between observed and calculated frequencies. On the basis of the comparison between calculated and experimental results, assignments of fundamental modes were examined. Copyright © 2009 John Wiley & Sons, Ltd.     

NIR‐FT Raman and FT‐IR spectral investigations of the nonlinear optical chromophore p‐bromoacetanilide

Vibrational spectral analysis of the hydrogen‐bonded nonlinear optical (NLO) material p‐bromo acetanilide (PBA) was carried out using NIR‐FT‐Raman and FT‐IR spectroscopy. Ab initio molecular orbital computations were performed at HF/6‐31G (d) level to derive equilibrium geometry, vibrational wavenumbers, intensities and first hyperpolarizability. The lowering of the imino stretching wavenumbers suggests the existence of strong intermolecular N H···O hydrogen bonding, which was substantiated by the natural bond orbital (NBO) analysis. The vibrational spectra confirm that the charge‐transfer interaction between the  NHCOCH₃ group and—Br through phenyl ring is responsible for simultaneous strong IR and Raman activation of the ring mode 8a. Vibrational analysis indicates that the lowering of stretching wavenumbers of methyl group due to electronic effects simultaneously caused by induction and hyperconjugation is due to the presence of the oxygen atom. The presence of blue‐shifting H‐bonds of CH stretching wavenumbers, simultaneous activation of carbonyl stretching mode, the strong activity of low‐wavenumber H‐bond stretching vibrations and the role of intramolecular charge transfer in making the molecule NLO active have been analyzed on the basis of the vibrational spectral features. Copyright © 2007 John Wiley & Sons, Ltd.     

Vibrational spectra and structural studies of nonlinear optical crystal ammonium D,L‐tartrate: a density functional theoretical approach

Single crystals of ammonium D , L ‐tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single‐crystal X‐ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH₄⁺ stretching wavenumbers indicate the formation of inter‐ and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular structure,NMR and vibrational spectral analysis of 2,4‐difluorophenol by ab initio HF and density functional theory

Quantum chemical calculations of energies, geometries and vibrational wavenumbers of 2,4‐difluorophenol (2,4‐DFP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6‐311G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with related molecules. The best level of theory in order to reproduce the experimental wavenumbers is the B3LYP method with the 6‐311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of 2,4‐DFP is also reported. The entropy of the title compound was also performed at HF/6‐311G(d,p) and B3LYP/6‐311G(d,p) levels of theory. The isotropic chemical shift computed by ¹H, ¹³C NMR analyses also shows good agreement with experimental observations. The theoretical spectrograms for FT‐IR and FT‐Raman spectra of the title molecule have been constructed. Copyright © 2009 John Wiley & Sons, Ltd.     

FT‐IR,FT‐Raman,and computational calculations of 4‐chloro‐2‐(3‐chlorophenyl carbamoyl)phenyl acetate

FT‐IR and FT‐Raman spectra of 4‐chloro‐2‐(3‐chlorophenylcarbamoyl) phenyl acetate were studied. Vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes and the normal modes are assigned by potential energy distribution (PED) calculations. Simultaneous IR and Raman activation of the CO stretching mode shows the charge transfer interaction through a π‐conjugated path. Optimized geometrical parameters of the title compound are in agreement with the reported values. Analysis of the phenyl ring modes shows that C C stretching mode is equally active as strong bands in both IR and Raman, which can be interpreted as the evidence of intramolecular charge transfer via conjugated ring path and is responsible for hyperpolarizability enhancement leading to nonlinear optical activity. The red‐shift of the NH‐stretching wavenumber in the infrared spectrum from the computed wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectroscopy investigation using density functional theory on 7‐chloro‐3‐methyl‐2H‐1,2,4‐ benzothiadiazine 1,1‐dioxide

The solid phase Fourier transform infrared (FTIR) and Fourier transform (FT) Raman spectral analysis of 7‐chloro‐3‐methyl‐2H‐1,2,4‐benzothiadiazine 1,1‐dioxide (diazoxide), an antihypertensive agent was carried out along with density functional computations. The optimized geometry, wavenumber and intensity of the vibrational bands of diazoxide were obtained by DFT‐B3LYP level of theory with complete relaxation in the potential energy surface using 6‐31G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational wavenumbers calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated wavenumbers are found to be in good agreement. The experimental spectra coincide satisfactorily with those of calculated spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectral studies on charge transfer and ionic hydrogen‐bonding interactions of nonlinear optical material L‐arginine nitrate hemihydrate

The near infrared Fourier‐transform (NIR FT)‐Raman and Fourier‐transform infrared (FT‐IR) spectroscopies supported by HF/6‐31G(d) computations have been employed to derive equilibrium geometry, vibrational wavenumbers and the first hyperpolarizability of the nonlinear optical (NLO) material, L ‐arginine nitrate (LAN) hemihydrate. The reasonable NLO efficiency, predicted for the first time in this novel compound, has been confirmed by Kurtz–Perry powder second harmonic generation (SHG) experiments. The changes in the atomic charge distribution among different groups due to the presence of strong electronegative atoms and the shrinking of N O bonds of nitrate anion and C N bonds of guanidyl group have been analyzed. The splitting of the carboxylate stretching modes, blue shifting of methine vibrations and the electronic effects such as backdonation and induction on the methylene hydrogen atoms have also been examined in detail. The intense low wavenumber H‐bond Raman vibrations due to electron–phonon coupling and nonbonded interactions in making the LAN molecule NLO active have been discussed based on the vibrational spectral features. The natural bond orbital (NBO) analysis and HF computations confirm the occurrence of strong intra‐ and intermolecular N H·O and O H·O ionic hydrogen bonding between charged species providing the noncentrosymmetric structure in the LAN crystal. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐IR,FT‐Raman,SERS spectra and computational calculations of 4‐ethyl‐N‐(2′‐hydroxy‐5′‐nitrophenyl)benzamide

Fourier transform infrared (FT‐IR) and FT‐Raman spectra of 4‐ethyl‐N‐(2′‐hydroxy‐5′‐nitrophenyl)benzamide were recorded and analyzed. A surface‐enhanced Raman scattering (SERS) spectrum was recorded in silver colloid. The vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes. The red shift of the NH stretching wavenumber in the infrared spectrum from the computational wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighboring oxygen atom. The simultaneous IR and Raman activation of the CO stretching mode gives the charge transfer interaction through a π‐conjugated path. The presence of methyl modes in the SERS spectrum indicates the nearness of the methyl group to the metal surface, which affects the orientation and metal molecule interaction. The first hyperpolarizability and predicted infrared intensities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive subject for future studies of nonlinear optics. Optimized geometrical parameters of the title compound are in agreement with reported structures. Copyright © 2009 John Wiley & Sons, Ltd.     

DFT simulations and vibrational analysis of FTIR and FT‐Raman spectra of 2‐amino‐4,6‐dihydroxypyrimidine

This work deals with the vibrational spectroscopy of 2‐amino‐4,6‐dihydroxy pyrimidine (ADHP) by means of quantum chemical calculations. The mid‐ and far FTIR and FT‐Raman spectra were measured in the condensed state. The fundamental vibrational wavenumbers and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6‐311 + G** methods and basis set combinations, and were scaled using various scale factors, which yielded good agreement between the observed and calculated wavenumbers. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on the scaled density functional force field. The results of the calculations were applied to simulate the infrared and Raman spectra of the title compound, which showed excellent agreement with the observed spectra. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐Raman,FT‐IR spectral and DFT studies on 6, 8‐dichloroflavone and 6, 8‐dibromoflavone

In this study, experimental and theoretical vibrational spectral results of the molecular structures of 6,8‐dichloroflavone (6,8‐dcf) and 6,8‐dibromoflavone (6,8‐dbf) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together between 4000 and 400 cm⁻¹ and 3500–5 cm⁻¹ regions, respectively. The molecular geometry and vibrational wavenumbers of 6,8‐dcf and 6,8‐dbf in their ground state have been calculated by using DFT/B3LYP functional, with 6‐31 + + G(d,p) basis set used in calculations. All calculations were performed with Gaussian03 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities are also reported. Copyright © 2009 John Wiley & Sons, Ltd.     

Structural and vibrational analyses of 2‐(2‐benzofuranyl)‐2‐imidazoline

We have studied 2‐(2‐benzofuranyl)‐2‐imidazoline (BFI) and characterized it by using infrared and Raman spectroscopies. The density functional theory (DFT) method together with Pople's basis set shows that two conformers exist for the title molecule as have been theoretically determined in the gas phase and that, probably, an average of both conformations is present in the solid phase. The harmonic vibrational wavenumbers for the optimized geometry of the latter conformer were calculated at the B3LYP/6‐31G* level in the proximity of the isolated molecule. For a complete assignment of the IR and Raman spectra in the compound in the solid phase, DFT calculations were combined with Pulay's scaled quantum mechanics force field (SQMFF) methodology in order to fit the theoretical wavenumbers to the experimental ones. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecular structure,vibrational spectroscopic,first‐order hyperpolarizability and HOMO,LUMO studies of 3‐hydroxy‐2‐naphthoic acid hydrazide

The Fourier‐transform infrared spectrum of 3‐hydroxy‐2‐naphthoic acid hydrazide (3H2NAH) was recorded in the region 4000–400 cm⁻¹. The Fourier‐transform Raman spectrum of 3H2NAH was also recorded in the region 3500–10 cm⁻¹. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 3H2NAH were carried out by density functional theory (DFT/B3LYP) method with 6‐31G(d,p) as basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The values of the electric dipole moment (µ) and the first‐order hyperpolarizability (β) of the investigated molecule were computed using ab initio quantum mechanical calculations. The UV spectrum was measured in ethanol solution. The calculation results also show that the 3H2NAH molecule might have microscopic nonlinear optical (NLO) behavior with non‐zero values. A detailed interpretation of the infrared and Raman spectra of 3H2NAH is also reported based on total energy distribution (TED). 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 also been constructed. Copyright © 2009 John Wiley & Sons, Ltd.