Novel green synthesis of S-doped TiO2 nanoparticles using Malva parviflora plant extract and their photocatalytic, antimicrobial and antioxidant activities under sunlight illumination.

Visible-light-responsible S-doped TiO2(GST) nanoparticles (NPs) are synthesized via sol-gel process, and an aqueous extract of Malva parviflora (MP) plant is used as the green and versatile medium with excellent reducing and capping properties to facilitate the S-doping and crystal growth of anatase. Compared with the counterpart (CST) derived from the conventional organic solvent. GST show a smaller average particle size (20.3 vs. 29.5 nm) with a larger surface area (135 vs 95 m2/g), together with the more significant red shift to longer wavelength in the visible light region. XPS analysis shows Ti4+ cations are substituted by S6+ ions into the lattice structure of TiO2 for both samples. The photodynamics of CST and GST catalysts are examined by electron paramagnetic resonance (EPR) spectroscopy, which shows the surface Ti3+ sites can be oxidized easily by the surface adsorbed O2 molecules, forming O2- radicals. Their photocatalytic activities (PCA) are evaluated by degrading methyl orange (MO) dye under the visible light irradiation. GST exhibit higher PCA in MO bleaching and chemical oxygen demand (COD) reduction. In addition, antimicrobial and antioxidant assays of CST and GST NPs also show that the irradiated NPs samples show higher antibacterial activities. GST NPs have a higher antibacterial activity than CST NPs against all tested bacteria and the minimum inhibitory concentration (MIC) is optimized to 25 µg/mL. The in-vitro antioxidant activity evaluated by the radical cation de-colorization test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) further demonstrates that GST NPs give a better antioxidant activity.

Raman, infrared and NMR spectral analysis, normal coordinate analysis and theoretical calculations of 5-(methylthio)-1,3,4-thiadiazole-2(3H)-thione and its thiol tautomer.

Raman (3400-100 cm(-1)) and infrared (4000-200 cm(-1)) spectra of 5-(methylthio)-1,3,4-thiadiazole-2(3H)-thione (C3H4N2S3; MTT) were measured in the solid state, and the (1)H/(13)C NMR spectra were obtained in DMSO-d6. Initially, twelve structures were proposed as a result of thiol-thione tautomerism and the internal rotation about the C-S bonds. The energies and vibrational frequencies of the optimized structures were calculated using the 6-31G(d) basis set with the methods of MP2 and DFT/B3LYP with Gaussian 98 quantum calculations. Additionally, (1)H/(13)C NMR chemical shifts were predicted for the thiol (structure 5) and thione (structure 9) tautomers by means of B3LYP/6-311+G(d,p) calculations utilizing the GIAO approximation and the PCM solvation model. After complete relaxation of twelve candidate isomers, the thione tautomer (structure 9) was favored owing to its low energy and its predicted real spectral frequencies. These results agree with the recorded infrared and Raman results, in addition to the observed/calculated (1)H and (13)C NMR spectra. Aided by normal coordinate analysis and potential energy distributions (PEDs), complete vibrational assignments have been proposed for all observed fundamentals for the thione tautomer. With the aid of MP2/6-31G(d) potential surface scans, CH3, CH3S, and SH barriers to internal rotations were estimated with the optimized structural parameters from the MP2 method with the 6-31G(d) basis set. The results are discussed herein and compared with similar model compounds whenever appropriate.

Analysis of UV and vibrational spectra (FT-IR and FT-Raman) of hexachlorocyclotriphosphazene based on normal coordinate analysis, MP2 and DFT calculations.

The Raman (1400-100 cm(-1)) and infrared (4000-400 cm(-1)) of solid hexachlorocyclotriphosphazene, P(3)N(3)Cl(6) (HCCTP) were recorded. The conformational energies were calculated using MP2 and DFT (B3LYP and B3PW91) methods utilizing a variety of basis sets up to 6-311+G(d). On the basis of D(3h) symmetry, the simulated vibrational spectra of P(3)N(3)Cl(6) from MP2 and DFT methods were in excellent agreement with those obtained experimentally. Additionally, Frontier Molecular Orbitals and electronic transitions were predicted using steady state and time dependent DFT(B3LYP)/PCM calculations respectively, each employing the 6-311+G(d,p) optimized structural parameters. The predicted wavelengths were in excellent agreement with experimental values when CH(2)Cl(2) was used as solvent. The (14)N and (31)P chemical shifts were predicted with B3LYP/6-311+G(2d,p) calculations using the GIAO technique with solvent effect modeled using the PCM method. The computed structural parameters of the planar P(3)N(3)Cl(6) (D(3h)) agree well with experimental values from both X-ray and electron diffraction data with slight distortions observed due to lattice defects in the solid phase. The experimental/computational results favor a slightly distorted D(3h) symmetry for the title compound in the gas and solid phases and in solution (τPNPN and τNPNP ranged from 0.018° to 0.90°). Aided by normal coordinate analysis, and the simulated vibrational spectra utilizing MP2, B3LYP and B3PW91 methods at 6-31G(d) basis set, revised and complete vibrational assignments for all fundamentals are provided herein.

Vibrational assignments, normal coordinate analysis, B3LYP calculations and conformational analysis of methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate.

The Raman and infrared spectra of solid methyl-5-amino-4-cyano-3-(methylthio)-1H-pyrazole-1-carbodithioate (MAMPC, C7H8N4S3) were measured in the spectral range of 3700-100 cm(-1) and 4000-200 cm(-1) with a resolution of 4 and 0.5 cm(-1), respectively. Room temperature 13C NMR and (1)H NMR spectra from room temperature down to -60 °C were also recorded. As a result of internal rotation around C-N and/or C-S bonds, eighteen rotational isomers are suggested for the MAMPC molecule (Cs symmetry). DFT/B3LYP and MP2 calculations were carried out up to 6-311++G(d,p) basis sets to include polarization and diffusion functions. The results favor conformer 1 in the solid (experimentally) and gaseous (theoretically) phases. For conformer 1, the two -CH3 groups are directed towards the nitrogen atoms (pyrazole ring) and CS, while the -NH2 group retains sp2 hybridization and C-CN bond is quasi linear. To support NMR spectral assignments, chemical shifts (δ) were predicted at the B3LYP/6-311+G(2d,p) level using the method of Gauge-Invariant Atomic Orbital (GIAO) method. Moreover, the solvent effect was included via the Polarizable Continuum Model (PCM). Additionally, both infrared and Raman spectra were predicted using B3LYP/6-31G(d) calculations. The recorded vibrational, 1H and 13C NMR spectral data favors conformer 1 in both the solid phase and in solution. Aided by normal coordinate analysis and potential energy distributions, confident vibrational assignments for observed bands have been proposed. Moreover, the CH3 barriers to internal rotations were investigated. The results are discussed herein are compared with similar molecules whenever appropriate.

Conformational stability, vibrational assignmenents, barriers to internal rotations and ab initio calculations of 2-aminophenol (d 0 and d3).

The Raman (3700-100 cm(-1)) and infrared (4000-400 cm(-1)) spectra of solid 2-aminophenol (2AP) have been recorded. The internal rotation of both OH and NH2 moieties produce ten conformers with either Cs or C1 symmetry. However, the calculated energies as well as the imaginary vibrational frequencies reduce rotational isomerism to five isomers. The molecular geometry has been optimized without any constraints using RHF, MP2 and B3LYP levels of theory at 6-31G(d), 6-311+G(d) and 6-31++G(d,p) basis sets. All calculations predict 1 (cis; OH is directed towards NH2) to be the most stable conformation except RHF/6-31++G(d,p) basis set. The 1 (cis) isomer is found to be more stable than 8 (trans; OH is away from the NH2 moiety and the NH bonds are out-of-plane) by 1.7 kcal/mol (598 cm(-1)) as obtained from MP2/6-31G(d) calculations. Aided by experimental and theoretical vibrational spectra, cis and trans 2AP are coexist in solution but cis isomer is more likely present in the crystalline state. Aided by MP2 and B3LYP frequency calculations, molecular force fields, simulated vibrational spectra utilizing 6-31G(d) basis set as well as normal coordinate analysis, complete vibrational assignments for HOC6H4NH2 and DOC6H4ND2 have been proposed. Furthermore, we carried out potential surface scan, to determine the barriers to internal rotations of NH2 and OH groups. All results are reported herein and compared with similar molecules when appropriate.