On the molecular basis of HO/DMSO eutectic mixtures by using phenol compounds as molecular sensors: a combined NMR and DFT study.

NMR and DFT studies of phenol compounds as molecular sensors were carried out to investigate HO/DMSO eutectic mixtures at a molecular level. The experimental H NMR chemical shifts of the OH groups, δ(OH), of phenol, paracoumaric acid, and vanillic acid show maximum deshielding and, thus, hydrogen bond interactions in the range of mole fractions 0.20 < χ(DMSO) < 0.

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric -Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate.

A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and H-C Heteronuclear Multiple Bond Correlation (HMBC) NMR techniques has been employed for the identification of methyl linolenate primary oxidation products without the need for laborious isolation of the individual compounds. Complex hydroperoxides and diastereomeric -hydroperoxides were identified and quantified. Strongly deshielded C-O-O-H H-NMR resonances of diastereomeric -hydroperoxides in the region of 8.

DFT Calculations of H- and C-NMR Chemical Shifts of Geometric Isomers of Conjugated Linoleic Acid (18:2 ω-7) and Model Compounds in Solution.

A density functional theory (DFT) study of the H- and C-NMR chemical shifts of the geometric isomers of 18:2 ω-7 conjugated linoleic acid (CLA) and nine model compounds is presented, using five functionals and two basis sets. The results are compared with available experimental data from solution high resolution nuclear magnetic resonance (NMR). The experimental H chemical shifts exhibit highly diagnostic resonances due to the olefinic protons of the conjugated double bonds.

The unique catalytic role of water in aromatic C-H activation at neutral pH: a combined NMR and DFT study of polyphenolic compounds.

Direct activation of aromatic C-H bonds in polyphenolic compounds in a single step, without the use of late transition metals, is demonstrated with the use of D2O and common phosphate buffer at neutral pD and near ambient temperatures. Detailed variable temperature and pD 1H NMR studies were carried out to investigate, for the first time, the Gibbs activation energy (ΔG‡), the activation enthalpy (ΔH‡), and activation entropy (TΔS‡) of H/D exchange reactions of the natural product catechin and the model compounds resorcinol and phloroglucinol. NMR and DFT calculations support a catalytic cycle comprising two water molecules in a keto-enol tautomeric process.

-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies.

A number of -pyridinyl oxime carbamate derivatives were prepared upon the reaction of the corresponding oximes with isocyanates. These novel compounds reacted photochemically in the presence of supercoiled plasmid DNA. Structure-activity relationship (SAR) studies revealed that the substituent on the imine group was not affecting the extend of the DNA damage, whereas the substituent of the carbamate group was critical, with the halogenated derivatives to be able to cause extensive single and double stranded DNA cleavages, acting as "synthetic nucleases", independently of oxygen and pH.

Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and H-NMR Chemical Shifts.

Detailed solvent and temperature effects on the experimental H-NMR chemical shifts of the natural products chrysophanol (), emodin (), and physcion () are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.

Ground- and triplet excited-state properties correlation: a computational CASSCF/CASPT2 approach based on the photodissociation of allylsilanes.

Excited-state properties, although extremely useful, are hardly accessible. One indirect way would be to derive them from relationships to ground-state properties which are usually more readily available. Herewith, we present quantitative correlations between triplet excited-state (T₁) properties (bond dissociation energy, D₀(T₁), homolytic activation energy, E(a)(T₁), and rate constant, k(r)) and the ground-state bond dissociation energy (D₀), taking as an example the photodissociation of the C-Si bond of simple substituted allylsilanes CH₂=CHC(R¹R²)-SiH₃ (R¹ and R² = H, Me, and Et).