Thiol-thione tautomeric analysis, spectroscopic (FT-IR, Laser-Raman, NMR and UV-vis) properties and DFT computations of 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule.

In this study, the 5-(3-pyridyl)-4H-1,2,4-triazole-3-thiol molecule (C7H6N4S) molecule has been characterized by using FT-IR, Laser-Raman, NMR and UV-vis spectroscopies. Quantum chemical calculations have been performed to investigate the molecular structure (thione-thiol tautomerism), vibrational wavenumbers, electronic transition absorption wavelengths in DMSO solvent and vacuum, proton and carbon-13 NMR chemical shifts and HOMOs-LUMOs energies at DFT/B3LYP/6-311++G(d,p) level for all five tautomers of the title molecule. The obtained results show that the calculated vibrational wavenumbers, NMR chemical shifts and UV-vis wavelengths are in a good agreement with experimental data.

The new Schiff base 4-[(4-Hydroxy-3-fluoro-5-methoxy-benzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one: experimental, DFT calculational studies and in vitro antimicrobial activity.

The synthesized Schiff base, 4-[(4-Hydroxy-3-fluoro-5-methoxy-benzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (I), has been characterized by (13)C NMR, (1)H NMR, 2D NMR ((1)H-(1)H COSY and (13)C APT), FT-IR, UV-vis and X-ray single-crystal techniques. Molecular geometry of the compound I in the ground state, vibrational frequencies and chemical shift values have been calculated by using the density functional method (DFT) with 6-311++G(d,p) basis set. The obtained results indicate that optimized geometry can well reflect the crystal structural parameters. The differences between experimental and calculated results of FT-IR and NMR have supported the existence of intermolecular (O-H⋯O type) and intramolecular (C-H⋯O type) hydrogen bonds in the crystal structure. Molecular electrostatic potential (MEP), frontier molecular orbital analysis (HOMO-LUMO) and electronic absorption spectra were carried out at B3LYP/6-311G++(d,p). HOMO-LUMO electronic transition of 3.92eV is due to contribution of the bands the n→π∗. The antimicrobial activity of the compound I was determined against the selected 11 bacteria and 8 fungi by microdilution broth assay with Alamar Blue. In vitro studies showed that the compound I has no antifungal effect for selected fungal isolates. However, the compound I shows remarkable antibacterial effect for the bacteria; Streptococcus pneumoniae, Haemophilus influenzae and Enterococcus faecalis.

DFT calculations, spectroscopy and antioxidant activity studies on (E)-2-nitro-4-[(phenylimino)methyl]phenol.

We have reported synthesis and characterization of (E)-2-nitro-4-[(phenylimino)methyl]phenol by using X-ray crystallographic method, FT-IR and UV-vis spectroscopies and density functional theory (DFT). Optimized geometry and vibrational frequencies of the title compound in the ground state have been computed by using B3LYP with the 6-311G+(d,p) basis set. HOMO-LUMO energy gap, Non-linear optical properties and NBO analysis of the compound are performed at B3LYP/6-311G+(d,p) level. Additionally, as remarkable properties, antioxidant activity of the title compound (CMPD) has been determined by using different antioxidant test methods i.e. ferric reducing antioxidant power (FRAP), hydrogen peroxide scavenging (HPSA), free radical scavenging (FRSA) and ferrous ion chelating activities (FICA). When compared with standards (BHA, BHT, and α-tocopherol), we have concluded that CPMD has effective FRAP, HPSA, FRSA and FICA.

Isolation, characterization, spectroscopic properties and quantum chemical computations of an important phytoalexin resveratrol as antioxidant component from Vitis labrusca L. and their chemical compositions.

In this study, isolation and characterization of trans-resveratrol (RES) as an antioxidant compound were carried out from VLE, VLG and VLS. Furthermore, antioxidant activities were evaluated by using six different methods. Finally, total phenolic, flavonoid, ascorbic acid, anthocyanin, lycopene, ß-carotene and vitamin E contents were carried out. In addition, the FT-IR, (13)C and (1)H NMR chemical shifts and UV-vis. spectra of trans-resveratrol were experimentally recorded. Quantum chemical computations such as the molecular geometry, vibrational frequencies, UV-vis. spectroscopic parameters, HOMOs-LUMOs energies, molecular electrostatic potential (MEP), natural bond orbitals (NBO) and nonlinear optics (NLO) properties of title molecule have been calculated by using DFT/B3PW91 method with 6-311++G(d,p) basis set in ground state for the first time. The obtained results show that the calculated spectroscopic data are in a good agreement with experimental data.

Experimental and theoretical investigation of the molecular and electronic structure of 3-ethoxy-4-isopropylaminocyclobut-3-ene-1,2-dione.

The title compound, 3-ethoxy-4-isopropylaminocyclobut-3-ene-1,2-dione (EIAC) has been synthesized and characterized by NMR, FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. The (1)H NMR spectra were recorded at 300 K and 315 K in CDCl(3) to determine syn/anti conformers of the compound EIAC. Density functional theory (DFT) calculations, optimized geometrical parameters, vibrational frequencies and chemical shift values of syn/anti conformer in CDCl(3) have been performed at B3LYP/6-311G(d) level, and compared with the experimental data. The values provided with the calculations support the experimental data of the compound EIAC. The presence of NH⋯O type intermolecular H bond can be perceived from the difference between experimental calculations and results of FT-IR and NMR calculations. In addition, B3LYP/6-311G(d) basis set has been used to calculate the molecular electrostatic potential, frontier molecular orbitals and electronic absorption spectra. HOMO-LUMO electronic transition of 5.12 eV is derived from the contribution of the bands n→σ(*) or π→π(*). FT-IR, NMR and X-ray spectral results and additionally DFT calculations exhibit that the compound EIAC exists in keto-enamine tautomeric form. The experimental (1)H NMR spectra recorded at 300 K and 315 K and theoretical (1)H NMR data indicate that the compound EIAC is in syn conformer.

Experimental (13C NMR, 1H NMR, FT-IR, single-crystal X-ray diffraction) and DFT studies on 3,4-bis(isoproylamino)cyclobut-3-ene-1,2-dione.

In this work, 3,4-bis(isoproylamino)cyclobut-3-ene-1,2-dione C(10)H(16)N(2)O(2) (I), was synthesized and characterized by (13)C NMR, (1)H NMR, FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. DFT method with 6-31G(d,p) basis set has been used to calculate the optimized geometrical parameters, atomic charges, vibrational frequencies and chemical shift values. The calculated vibrational frequencies and chemical shift values are compared with experimental FT-IR and NMR spectra. The results of the calculation shows good agreement between experimental and calculated values of the compound I. The existence of N-H⋯O type intermolecular ve C-H⋯O type intramolecular hydrogen bonds can be deduced from differences between experimental and calculated results of FT-IR and NMR. In addition, the molecular electrostatic potential map and frontier molecular orbitals and electronic absorption spectra were performed at B3LYP/6-31G(d,p) level of theory. HOMO-LUMO electronic transition of 4.90 eV are derived from the contribution of the bands π→π* and n→π* The spectral results obtained from FT-IR, NMR and X-ray of I revealed that the compound I is in predominantly enamine tautomeric form, which was supported by DFT calculations.