Tautomer In Solid State Research Articles

DFT Study on the Electronic Properties, Spectroscopic Profile, and Biological Activity of 2-Amino-5-trifluoromethyl-1,3,4-thiadiazole with Anticancer Properties.

Extensive investigation on the molecular and electronic structure of 2-amino-5-trifluoromethyl-1,3,4-thiadiazole in the ground state and in the first excited state has been performed. The energy barrier corresponding to the conversion between imino and amino tautomers has been calculated, which indicates the existence of amino tautomer in solid state for the title compound. The FT–Raman and FT-IR spectra were recorded and compared with theoretical vibrational wavenumbers, and a good coherence has been observed. The MESP map, dipole moment, polarizability, and hyperpolarizability have been calculated to comprehend the properties of the title molecule. High polarizability value estimation of the title compound may enhance its bioactivity. Natural bonding orbital analysis has been done on monomer and dimer to investigate the charge delocalization and strength of hydrogen bonding, respectively. Strong hydrogen bonding interaction energies of 17.09/17.49 kcal mol–1 have been calculated at the B3LYP/M06-2X functional. The UV–vis spectrum was recorded and related to the theoretical spectrum. The title compound was biologically examined for anticancer activity by studying the cytotoxic performance against two human cancer cell lines (A549 and HeLa) along with the molecular docking simulation. Both molecular docking and cytotoxic performance against cancer cell lines show positive outcomes, and the title compound appears to be a promising anticancer agent.

Synthesis, spectral characterization, DFT calculations, antimicrobial activity and molecular docking of 4-bromo-2-((2-hydroxy-5-methylphenylimino)methyl)phenol and its V(V) complex

VO(acac)2 reacted with a new ONO tridentate Schiff base, 4-bromo-2-((2-hydroxy-5-methylphenylimino)methyl)phenol, (H2L) in methanol to afford a new V(V) complex, [VO(L)(MeO)(MeOH)]. Characterization by elemental analysis, molar conductivity, FT-IR, electronic spectroscopy, 1H NMR, single crystal X-ray and TGA studies indicated that the free ligand existed as its keto tautomer in solid state, while in the complex it was coordinated to the regular VO core in its deprotonated form (enol), as a tridentate anionic ligand. The vanadium center was also found to be 6-coordinated, in a distorted octahedral fashion with a deprotonated ligand and an oxygen atom of the methoxy group in the equatorial plane and an oxido ligand and an oxygen from methanol in the apical sites. DFT and NBO calculations were additionally performed and confirmed the experimental data. The synthesized ligand and its oxido-vanadium(V) complex exhibited satisfactory antimicrobial activities against some tested Gram-positive and Gram-negative bacteria, and fungus strain. In addition, the potential of these compounds as antimicrobial agents was investigated using molecular docking to glucosamine-6-phosphate (GlcN-6-P) synthase.

Synthesis, spectral studies of salicylidine-pyridines: Crystal and molecular structure of 2-[(1 E)-2-aza-2-(5-methyl(2-pyridyl)ethenyl)]-4-bromobenzen-1-ol

Schiff bases derived from different meta-substituted salicylaldehyde and 5-methylaminopyridine have been synthesized and characterized by elemental analysis, FT-IR, NMR and UV–vis techniques. NMR assignments were made using 1H, 13C NMR and aided by 2D HETCOR and HMBC heteronuclear correlation techniques. The UV–vis spectra of the compounds were found useful in understanding the existence of tautomeric equilibria [phenol-imine (O–H⋯N) and keto-amine (O⋯H–N) forms] in polar and non-polar solvents. In order to rationalize the stabilization of tautomer in solid state, X-ray structure of 2-[(1 E)-2-aza-2-(5-methyl(2-pyridyl)ethenyl)]-4-bromobenzen-1-ol ( 6) was determined. According to our crystallographic result, it has enol-imine tautomeric form.

Synthesis, crystal structure and spectroscopic study of para substituted 2-hydroxy-3-methoxybenzalideneanilines

Eight Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde and different para substituted anilines have been synthesized and their structures were elucidated by physical measurements and FT-IR. NMR assignments were made using 1H, 13C NMR and aided by 2D COSY homonuclear, HMQC and HMBC heteronuclear correlation techniques. IR spectral analysis of the model compounds was found useful in understanding the degree of stabilization upon this series of enol-imino tautomers, which possess different substituents in the aniline fragment. In order to rationalize the stabilization of tautomer in solid state, the crystallography data of 1-{(4-methylphenylimino)methyl}- and 1-{(4-chlorophenylimino)methyl}-2-hydroxy-3-methoxyphenol were adopted wherein the 4-chloro (4-Cl) and 4-methyl (4-CH 3) containing compounds crystallized into orthorhombic lattice with a non-centrosymmetric space group P2 12 12 1. The relationship between the stabilization of bonding involved in heteronuclear six-membered ring of the tautomer and the conformation of the molecules in crystal phase was reported.

Facile enolisation of α-ketophosphonates

A number of α-ketophosphonate are prepared and shown to be easily enolised. An X-ray crystal structure determination of a β-phenyl-α-ketophosphonate shows the molecule to be present as hydrogen bonded dimers and demonstrates the presence of enol tautomer in solid state. α-ketophosphonate can be converted to the corresponding enolacetate under mild conditions. The enolacetate have the E-configuration exclusively.