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Nonlinear optical active L-leucinium squarate monohydrate single crystals were grown using the slow evaporation technique. The crystal structure was determined using the single crystal X-ray diffraction technique. FT-IR and FT-Raman spectra were recorded and analyzed. Meanwhile, the thermal characteristics of the sample were analyzed using TGA-DTA techniques. In addition, the equilibrium geometry, vibrational wavenumbers and first-order hyperpolarizability were calculated with the aid of the density functional theoretical method. The red-shift of NH 3 + stretching wavenumbers indicates the formation of inter- and intra-molecular hydrogen bonding in the molecule. Similarly, the blue-shift in the C-H stretching wavenumbers is due to the presence of C-H ⋯ O hydrogen bonding. The natural bond orbital analysis confirms the occurrence of a strong intermolecular hydrogen bonding that is responsible for the stabilization of the molecule. Molecular electrostatic potential maps help to predict the electrophilicity and nucleophilicity groups in the molecule. The HOMO-LUMO energy gap value suggests the possibility of charge transfer within the molecule. The SHG conversion efficiency was investigated using the Kurtz and Perry method and was found to be higher than that of urea. The intercontacts in the crystal structure were analyzed using the Hirshfeld surfaces analysis method. The thermodynamic properties at different temperatures were also calculated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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 OO and intramolecular CO hydrogen bonds. The electronic absorption spectra with different solvents have been investigated in combination with time-dependent density functional theory calculation. The pK a values of phenoxy acetic acids were compared. [Copyright &y& Elsevier]

Abstract The drug action of ester type local anesthetic (LA) procaine hydrochloride (PRC HCl) is activated by blocking Na+ ion flow when it binds to the ion channel in the ligand gated sodium ion channel protein. Büchi's model, explains binding action of ester type LA drug with receptor in terms of charge transfer, dipole-dipole, hydrogen bonding and van der Waals interactions through lipophilic, ester and hydrophilic moieties. The present work investigates molecular structural and vibrational spectral features of para amino benzoate group, ester part and tertiary amino group respectively belonging to lipophilic, ester and hydrophilic moieties, accountable for the binding of drug to sodium channel. The electron transport mechanism through the ring responsible for structural deviation from benzenoid to quinonoid form and consequent dipolar nature of carbonyl group have been investigated, based on the analysis of XRD, DFT computed molecular structure, 8a ring mode and NBO charges. The characteristic UV absorption peaks and vibrational marker bands of LA drugs have been identified and the charge transfer interaction responsible for lipophilic binding has been investigated. The blocking of Na+ in the ion channel has been probed using attractive and repulsive energy profile. The molecular polarizability has been computed to substantiate the correlation between the structure activity relationship of LA drug molecule and molecular polarizability. The low toxicity of PRC HCl was evaluated using in vitro cytotoxicity study, confirming it as a potential short acting local anesthetic. Graphical Abstract Unlabelled Image Highlights • Vibrational spectral account of Büchi's model for local anesthetic drug action • Role of electron transport in benzenoid to quinonoid change and carbonyl activity • Blocking of Na+ ion in channel probed with attractive and repulsive energy profile • Charge transfer interaction responsible for lipophilic binding analyzed • IR and Raman spectral markers for ester type local anesthetics identified [ABSTRACT FROM AUTHOR]