Augmenting the effect of solvents on optical nonlinearity by spectroscopic, DFT, solvatochromism and z-scan studies of push-pull chalcone: (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one.

In this article, the structural and nonlinear optical behaviour of a chalcone derivative, (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one have been studied. FT-IR, FT-Raman, and NMR spectroscopy were analyzed to validate the molecular structure. To predict the nonlinear optical characteristics of the chalcone, the DFT approach was used and the experimental results were corroborated by the computations. The bathochromic shift is obtained in linear absorbance spectra and is validated using TD-DFT. Also, the broad emission in the blue region demonstrates the blue light emission property of the sample. Using the finite-field method, the dipole moments, polarizability, first-order and second-order hyperpolarizability parameters have been computed. Ground and excited state dipole moments were quantified by solvatochromism. The third-order nonlinear optical characteristics of chalcone in polar and non-polar solvent media were examined using the open/closed-aperture z-scan technique. The chalcone displayed considerable two-photon absorption with a positive nonlinear absorption coefficient and a positive index of refraction due to the self-focussing effect. Furthermore, the optical limiting study manifests that the investigated chalcone might well be favourable for NLO applications.

Structural activity, fungicidal activity and molecular dynamics simulation of certain triphenyl methyl imidazole derivatives by experimental and computational spectroscopic techniques.

The main objective of the study is to analyze the structural behaviour and fungicidal activity of clotrimazole by experimental and theoretical spectroscopic techniques. Its computational results are correlated with three triphenyl imidazole derivative compounds. The clotrimazole-water complexes formed by hydrogen bonding interactions are investigated at the B3LYP/6-311G(d,p) level. The distributions of the vibrational bands are carried out with the help of normal coordinate analysis (NCA). Hirshfeld surface analysis of clotrimazole is done and the obtained finger print plots reveal the interactions within the compound. The stability of the compounds in water has been investigated by using molecular dynamics simulation (MDS). Molecular docking is done on the compounds in comparison with the native ligand (Lanosterol 14α-demethylase) and standard drug (fluconazole) to study the hydrogen bond energy interaction. The antifungal activity of clotrimazole is analyzed by using two fungal pathogens.

In-silico analysis of substituent effect on the static first order hyperpolarizability of electron donating mono substituted Chalcone derivatives.

Noncentrosymmetric π conjugated systems with suitable electron donor acceptor groups play a crucial role in material NLO activity. The influence of an electron donating mono substituent at the para position of the phenylene ring of chalcone was investigated as a resource for second harmonic generation. The geometrical optimization of 11 electron donating group substituted chalcones were performed using density functional theory at the B3LYP/6-311G(d,p) level and compared with experimental geometrical parameters of five reported chalcones. All the derivatives are transparent to visible radiation as shown by the electronic absorption spectra investigated by the TDDFT-CAM B3LYP/6-311G(d,p) method, and the maximum absorption wavelength was due to the πPhB → π* transition. The first order hyperpolarizability ßtot, calculated using the CAM B3LYP/6-311G(d,p) method, increases with the electron donating ability of the substituent, and the largest ßtot was observed for dimethylamino substituent. The Hammett substituent constant (σp) shows good linear correlation with ß, λmax, and Egap in the ground state. The Brown constant (σp+) was better correlated indicating the polarization of carbonyl group in the excited state. Frontier molecular orbitals also reveal the valence electron excitation. Correlation of σp with various parameters was analyzed to assess the property interrelationship with electronic reorganization in the molecule. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intramolecular interactions.

Structure and nonlinear optical property analysis of L-Methioninium oxalate: a DFT approach.

Infrared and FT-Raman spectra of the nonlinear optical material l-Methioninium Oxalate were recorded and analyzed. The optimized geometry, first-order hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of density functional theory method. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis followed by scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions leading to its nonlinear optical activity and charge delocalization were analyzed using natural bond orbital technique. Mulliken atomic charge and molecular electrostatic potential are also predicted. HOMO-LUMO energy gap value suggests the possibility of charge transfer within the molecule. The thermodynamic properties at different temperatures are also calculated.

FT-IR and FT-Raman spectra, MEP and HOMO-LUMO of 2,5-dichlorobenzonitrile: DFT study.

The experimental FT-IR and FT-Raman spectra of 2,5-dichlorobenzonitrile molecule were recorded at room temperature, and the results compared with quantum chemical theoretical values using MP2 and DFT methods. Molecular geometry, vibrational wavenumbers and thermodynamic parameters were calculated. With the help of specific scaling procedures for the computed wavenumbers, the experimentally observed FTIR and FT-Raman bands were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range and the error obtained was in general very low. Several general conclusions were deduced. The NBO analysis has been done and Molecular Electrostatic Potential (MEP) has been plotted.

Spectroscopic analysis and charge transfer interaction studies of 4-benzyloxy-2-nitroaniline insecticide: a density functional theoretical approach.

A widespread exploration on the intra-molecular charge transfer interaction through an efficient π-conjugated path from a strong electron-donor group (amino) to a strong electron-acceptor group (nitro) has been carried out using FTIR, FT-Raman, UV-Vis, fluorescence and NMR spectra on insecticide compound 4-benzyloxy-2-nitroaniline. Density functional theory method is used to determine optimized molecular geometry, harmonic vibrational wavenumbers and intensities using 6-311G(d,p) basis set by means of Gaussian 09W program suit. A comprehensive investigation on the sp(2) to sp(3) hybridization and non-planarity property has been performed. Natural bond orbital analysis is used to study the existence of C-H⋯O, N-H⋯O and C-H⋯π proper and improper hydrogen bonds. The HOMO and LUMO analysis reveals the possibility of charge transfer within the molecule. A complete assignment of the experimental absorption peaks in the ultraviolet region has also been performed. Isotropic chemical shifts of (13)C, (1)H, (15)N and (18)O NMR and nuclear spin-spin coupling constants have been computed using the gauge-invariant atomic orbital method. The biological activity of substituent amino and nitro groups are evident from the hydrogen bonds through which the target amino acids are linked to the drug as evidenced from molecular docking.

Vibrational spectroscopic studies and DFT computation of the nonlinear optical molecule L-Valinium formate.

The Fourier Transform Infrared and Raman spectra of the L-Valinium formate have been recorded and analyzed. The assignments of the bands of the vibrational spectra have been carried out with the aid of Normal Coordinate Analysis following the calculated quantum mechanical force field methodology. Optimized geometry of the molecule has computed using of Density Functional Theory method. Natural Bond Orbital Analysis, Mulliken's net charges and the atomic natural charges are also predicted. HOMO and LUMO energy gap value suggest the possibility of charge transfer within the molecule. The thermodynamic properties at different temperatures are also calculated.

FT-IR, FT-Raman spectra and other molecular properties of 3,5-dichlorobenzonitrile: a DFT study.

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.

Normal coordinate analysis and Nonlinear Optical Response of cross-conjugated system 4,4-Dimethyl Benzophenone.

FT-Raman and IR spectra of the nonlinear optical active crystal, 4,4-Dimethyl Benzophenone (4DMBP) have been recorded and analyzed The equilibrium geometry, harmonic vibrational wavenumbers of 4DMBP investigated with the help of density functional theory (DFT) method. 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 calculated hyperpolarizability value shows the nonlinear optical activity of the molecule. The value of HOMO-LUMO energy, Mulliken and the natural charges are calculated and analyzed. The Natural bond orbital analysis confirms the occurrence of intramolecular charge transfer interaction.

Vibrational spectral investigation and natural bond orbital analysis of pharmaceutical compound 7-Amino-2,4-dimethylquinolinium formate - DFT approach.

The molecular geometry, the normal mode frequencies and corresponding vibrational assignments, natural bond orbital analysis and the HOMO-LUMO analysis of 7-Amino-2,4-dimethylquinolinium formate in the ground state were performed by B3LYP levels of theory using the 6-31G(d) basis set. The optimised bond lengths and bond angles are in good agreement with the X-ray data. The vibrational spectra of the title compound which is calculated by DFT method, reproduces vibrational wave numbers and intensities with an accuracy which allows reliable vibrational assignments. The possibility of N-H⋯O hydrogen bonding was identified using NBO analysis. Natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction.

Structural conformations and density functional study on the intramolecular charge transfer based on vibrational spectra of 2,4-dihydroxy-N'-(4-methoxybenzylidene)benzohydrazide.

The NIR-FT Raman and FT-IR spectra of 2,4-dihydroxy-N'-(methoxybenzylidene) benzohydrazide (DMBBH) molecule have been recorded and analyzed. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level has been used to compute energies of different conformers of DMBBH to find out their stability, the optimized geometry of the most stable conformer and its vibrational spectrum. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra and calculated vibrational modes and potential energy distribution over the internal coordinates. The vibrational analysis confirm the charge transfer interaction between the phenyl rings through C=N-N skeleton. The broadening of the band at 1631 cm(-1) and the appearance of the band at 1556 cm(-1) strongly suggests the existence of proton equilibrium.

Simulation of a tetramer form of 5-chlorouracil: the vibrational spectra and molecular structure in the isolated and in the solid state by using DFT calculations.

A Raman and FT-IR study of the biomolecule 5-chlorouracil in the solid state was carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify the assignments of the experimentally observed bands in the spectra. Calculations in the monomer form and comparisons with the experimental data in Ar matrix were also carried out. The error in the calculated frequencies was analyzed and reduced by using scaling equations and scaling factors deduced from the uracil molecule. The calculations with the B3LYP method and with the 6-31G(d,p) and 6-311+G(2d,p) basis set, appear in general to be useful, when combining with a scaling equation procedure or with the specific scale factors, for interpretation of the general features of the IR and Raman spectra. The scaled values were used in the reassignment of the IR and Raman experimental bands. Comparison of the results with those determined in uracil and 5-halogenated derivatives were performed. The substitution at 5-position of the uracil ring by a chlorine atom has a little effect on the geometric parameters.

DFT computation and experimental analysis of vibrational and electronic spectra of phenoxy acetic acid herbicides.

An absolute vibrational analysis has been attempted on the basis of experimental FTIR and NIR-FT Raman spectra with calculated vibrational wavenumbers and intensities of phenoxy acetic acids. The equilibrium geometry, bonding features and harmonic vibrational wavenumbers have been calculated with the help of B3LYP method with Dunning correlation consistent basis set aug-cc-pVTZ. The electronic structures of molecular fragments were described in terms of natural bond orbital analysis, which shows intermolecular O-H···O and intramolecular C-H···O hydrogen bonds. The electronic absorption spectra with different solvents have been investigated in combination with time-dependent density functional theory calculation. The pKa values of phenoxy acetic acids were compared.

Molecular structure and vibrational spectral investigation of charge transfer NLO crystal naphthalene picrate for THz application.

Molecular structure and the vibrational spectra of Naphthalene Picrate have been calculated using density functional theoretical computation and compared with the experimental. The dipole moments (µ), polarizability (α), first hyperpolarizabilities (ß) second hyperpolarizability (γ) and frontier molecular orbital energies are computed at the DFT level. The frontier molecular orbital calculation shows the inverse relationship of HOMO-LUMO gap with the total static hyperpolarizability. The hyperpolarizability value reveals that these classes of organic compounds show very large non-linear optical properties. Natural Bond Orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction. Terahertz time-domain spectroscopy has been used to detect the absorption spectra in the frequency range from 0.2 to 1.5 THz.

Growth and vibrational spectral investigation of nonlinear optical crystal L-Argininum Perchlorate-DFT study.

Nonlinear optical active L-Argininum Perchlorate single crystals are grown by slow evaporation technique. The second-order NLO properties of the molecule are studied by Kurtz-Perry powder technique. FT-IR, FT-Raman spectra have been recorded and analyzed. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability have been calculated with the aid of density functional theoretical method. The NBO analysis explains the intramolecular interactions, electron densities within the molecule. It also confirms the presence of weak intermolecular C-H···O hydrogen bonding in the molecule. The blue-shift in CH stretching wavenumbers is due to the C-H···O hydrogen bonding. The Mulliken population analysis on atomic charges and the HOMO, LUMO energies were also calculated.

Vibrational spectral investigation and Natural Bond Orbital analysis of anti-rheumatoid drug ethyl 4-nitrophenylacetate--DFT approach.

Vibrational analysis of ethyl 4-nitrophenylacetate (ENPA) molecule was carried out using FT-IR and FT-Raman spectroscopic techniques. The equilibrium geometry, harmonic vibrational wave numbers, various bonding features have been computed using density functional theory. The calculated molecular geometry parameters have been compared with XRD data. The detailed interpretation of the vibrational spectra has been carried out by computing Potential Energy Distribution (PED). Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. The results show that the charge in the electron density (ED) in the σ(*) and π(*) antibonding orbitals and second order delocalization energies (E(2)) confirm the occurrence of ICT (intramolecular charge transfer) within the molecule. The simulated spectra satisfactorily coincide with the experimental spectra.

Vibrational spectra and density functional theoretical calculations on the anti-neurodegenerative drug: Orphenadrine hydrochloride.

Vibrational spectral analysis and quantum chemical computations based on density functional theory have been performed on the anti-neuro-degenerative drug Orphenadrine hydrochloride. The geometry, intermolecular hydrogen bond, and harmonic vibrational frequencies of the title molecule have been investigated with the help of B3LYP method. The calculated molecular geometry has been compared with the experimental data. The various intramolecular interactions have been exposed by natural bond orbital analysis. The distribution of Mulliken atomic charges and bending of natural hybrid orbitals also reflect the presence of intramolecular hydrogen bonding. The analysis of the electron density of HOMO and LUMO gives an idea of the delocalization and low value of energy gap indicates electron transport in the molecule and thereby bioactivity. Effective docking of the drug molecule with NMDA receptor subunit 3A also enhances its bioactive nature.

Vibrational spectra and natural bond orbital analysis of organic crystal L-prolinium picrate.

Vibrational spectral analysis and quantum chemical computations based on density functional theory (DFT) have been performed on the organic crystal L-prolinium picrate (LPP). The equilibrium geometry, various bonding features and harmonic vibrational wavenumbers of LPP have been investigated using B3LYP method. The calculated molecular geometry has been compared with the experimental data. The detailed interpretation of the vibrational spectra has been carried out with the aid of VEDA 4 program. The various intramolecular interactions confirming the biological activity of the compound have been exposed by natural bond orbital analysis. The distribution of Mulliken atomic charges and bending of natural hybrid orbitals associated with hydrogen bonding also reflects the presence of intramolecular hydrogen bonding thereby enhancing bioactivity. The analysis of the electron density of HOMO and LUMO gives an idea of the delocalization and low value of energy gap indicates electron transport in the molecule and thereby bioactivity. Vibrational analysis reveals the presence of strong O-H···O and N-H···O interaction between L-prolinium and picrate ions providing evidence for the charge transfer interaction between the donor and acceptor groups and is responsible for its bioactivity.

Electronic absorption and vibrational spectra and nonlinear optical properties of L-valinium succinate.

FT-Raman and FTIR techniques have been applied to investigate the potential nonlinear optical material l-valinium succinate. A detailed interpretation of the vibrational spectra was carried out with the aid of potential energy distribution analysis. Density functional theory is applied to explore the nonlinear optical properties of the molecule. Good consistency is found between the calculated results and the experimental data for IR and Raman spectra. The natural bond orbital analysis confirms the occurrence of strong intramolecular N-H⋯O hydrogen bonding.

DFT-based molecular modeling, NBO analysis and vibrational spectroscopic study of 3-(bromoacetyl)coumarin.

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.