Experimental and theoretical investigation of the molecular and electronic structure of 5-(4-aminophenyl)-4-(3-methyl-3-phenylcyclobutyl)thiazol-2-amine

A DFT study on the geometry, tautomerism and noncovalent interactions of the Mepivacaine drug with the pristine SWCNT and –COOH functionalized SWCNT

The Mepivacaine drug is used as a local anesthetic in dentistry, which could exist as three different tautomers. Herein, geometry, energy behavior as well as tautomerization of these tautomers have been investigated by employing density functional theory (DFT) and considering the solvent effects with the polarizable continuum model (PCM) model. The most stable tautomer of the Mepivacaine has a carbonyl and an –NH amine groups in its structure. The frontier orbitals and the energy gap of the molecule have been computed using the natural bond orbital analysis (NBO). Also, the armchair (5,5) single wall carbon nanotube (SWCNT) was used for investigation of the noncovalent interactions of the Mepivacaine molecule with the pristine SWCNT and the –COOH functionalized SWCNT in several forms. Geometries of the possible forms have been optimized. The most stable form for noncovalent interactions of the drug with each of the pristine and functionalized SWCNTs have been determined. The intermolecular H-bonds have essential role in energy behavior of the noncovalent interactions between the Mepivacaine drug and the investigated SWCNTs.

Structural and spectroscopic characterization of 4-(3-methyl-3-phenylcyclobutyl)-2-(2-propylidenehydrazinyl)thiazole: A combined experimental and DFT analysis

We investigated the structural and spectroscopic properties of the title compound by means of experimental and DFT quantum chemical methods. The crystal structure of compound was brought to light by single crystal X-ray diffraction method, and were characterized spectroscopically using FT-IR and NMR spectra. FT-IR spectrum in solid state was observed in the region 4000-400 cm(-1). The (1)H and (13)C NMR spectra were recorded in CDCl3 solution. The molecular geometry were those obtained from the X-ray structure determination was optimized using density functional theory (DFT/B3LYP) method with the 6-31G(d, p) and 6-31+G(d, p) basis sets in ground state. From the optimized geometry of the molecule, geometric parameters (bond lengths, bond angles, torsion angles), vibrational assignments and chemical shifts of the title compound have been calculated theoretically and compared with the experimental data. Although theoretical calculations were carried out in gas phase, no significant differences in these values.

A DFT investigation of structure, spectroscopic properties and tautomerism of the anticonvulsant drug Lyrica

The Lyrica (Pregabalin) is a novel anticonvulsant and neuropathic pain drug, which could exist as four possible conformers. Herein, employing density functional theory (DFT), and handling the solvent effects with the PCM model, the structural parameters, energetic behavior, natural bond orbital analysis (NBO), as well as tautomerism mechanization of the Lyrica are investigated. The L1 (-OH form) is the most stable conformer of the Lyrica, which can be tautomerized to the L5 (-NH form) tautomer. The tautomerism reaction includes an intramolecular-proton transfer, which affects considerably the structural parameters and atomic charges of the L1. The DFT-computed NMR chemical shifts and IR vibrational frequencies are good in agreement with the experimental values, confirming suitability of the optimized geometry for the Lyrica.

6-Phenyl-3-(4-pyridyl)-1,2,4-triazolo-[3,4-b][1,3,4]thiadiazole: synthesis, experimental, theoretical characterization and biological activities

The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) (1)H and (13)C NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree-Fock (HF) and density functional theory (DFT) methods with 6-31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters and the theoretical vibrational frequencies, and (1)H and (13)C NMR chemical shift values show good agreement with experimental data. To determine conformational flexibility, molecular energy profile of the title compound was obtained by HF/6-31G(d) and (DFT/B3LYP) calculations with respect to selected degree of torsional freedom, which was varied from -180° to +180° in steps of 10°. The energetic behavior of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provided more stable structure than Onsager's method. The title compound has been tested in vitro for biological effects.