S. Balachandran

Nonplanar property study of antifungal agent tolnaftate-spectroscopic approach.

Vibrational analysis of the thionocarbamate fungicide tolnaftate which is antidermatophytic, antitrichophytic and antimycotic agent, primarily inhibits the ergosterol biosynthesis in the fungus, was carried out using NIR FT-Raman and FTIR spectroscopic techniques. The equilibrium geometry, various bonding features, harmonic vibrational wavenumbers and torsional potential energy surface (PES) scan studies have been computed using density functional theory method. The detailed interpretation of the vibrational spectra has been carried out with the aid of VEDA.4 program. Vibrational spectra, natural bonding orbital (NBO) analysis and optimized molecular structure show the clear evidence for electronic interaction of thionocarbamate group with aromatic ring. Predicted electronic absorption spectrum from TD-DFT calculation has been compared with the UV-vis spectrum. The Mulliken population analysis on atomic charges and the HOMO-LUMO energy were also calculated. Vibrational analysis reveals that the simultaneous IR and Raman activation of the C-C stretching mode in the phenyl and naphthalene ring provide evidence for the charge transfer interaction between the donor and acceptor groups and is responsible for its bioactivity as a fungicide.

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.

Spectroscopic investigation and hydrogen-bonding analysis of triazinones.

AbstractNIR FT-Raman, FTIR and UV-vis spectra of the herbicide metamitron were recorded and analyzed. The aromaticities, equilibrium geometries, bonding features, electrostatic potentials, and harmonic vibrational wavenumbers of the monomers and dimers of triazinone derivatives were also investigated with the aid of BLYP/6-311 G(df, p) density functional theory. Features in the vibrational spectra were assigned with the aid of the VEDA.4 program. The calculated results were a good match to the experimental data obtained from FTIR, Raman, and electronic absorption spectra. Mulliken population analysis was performed on the atomic charges and the HOMO–LUMO energies were also calculated. NBO analysis highlighted the intra- and intermolecular N–H…O and C–H…O hydrogen bonds in the crystal structures of the triazinones. The solvent effect was calculated using time-dependent density functional theory in combination with the polarizable continuum model. FigureFT-Raman and IR, UV-Vis spectra were used to investigate bioactivity of triazinone derivatives. The vibrational analysis expounds the charge transfer interaction of the molecule. The solvent effects have been calculated using the time-dependent density functional theory in combination with the polarized continuum model. The intra and intermolecular N-H…O and C-H…O hydrogen bonds in the crystal structures of triazinone herbicides are also investigated.

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.