Application of vibrational correlation formalism to internal conversion rate: case study of Cu(n) (n = 3, 6, and 9) and H2/Cu3.

This work reports non-radiative internal conversion (IC) rate constants obtained for Cun with n = 3, 6, and 9 and H2 on Cu3. The Time-Dependent Density Functional Theory (TDDFT) method was employed with three different functionals in order to investigate the electronic structures and the absorption spectra. The performance of the generalized gradient approximation of Perdew, Burke and Ernzerhof (PBE) and the hybrid B3LYP and PBE0 exchange correlation functionals in combination with the SVP and the def2-TZVP basis sets was examined.

Antioxidant efficiency of oxovitisin, a new class of red wine pyranoanthocyanins, revealed through quantum mechanical investigations.

Oxovitisin is a natural antioxidant present in aged wine and comes from the chemical transformation undergone by anthocyanins and pyranoanthocyanins. Its antioxidant radical scavenging capacity was theoretically explored by density functional theory (DFT)/B3LYP methods. The O-H bond dissociation energy (BDE), the ionization potential (IP), the proton affinity (PA), and the metal-oxovitisin binding energy (BE) parameters were computed in the gas-phase and in water and benzene solutions.

A TDDFT investigation of bay substituted perylenediimides: absorption and intersystem crossing.

The conformational structure and electronic spectra properties of a series of bay substituted perylenediimides (PDI) derivatives have been investigated by means of density functional theory (DFT) and time-dependent DFT. The B3LYP and PBE0 hybrid exchange-correlation functionals were applied in conjunction with the double-ζ quality SVP basis set. These compounds are interesting for organic materials science and as photosensitizers in cancer phototherapy (PDT), because of their intense absorption in the visible region.

Detailed Investigation of the OH Radical Quenching by Natural Antioxidant Caffeic Acid Studied by Quantum Mechanical Models.

The effectiveness of naturally occurring antioxidant caffeic acid in the inactivation of the very damaging hydroxyl radical has been theoretically investigated by means of hybrid density functional theory. Three possible pathways by which caffeic acid may inactivate free radicals were analyzed: hydrogen abstraction from all available hydrogen atoms, hydroxyl radical addition to all carbon atoms in the molecule, and single electron transfer. The reaction paths were traced independently, and the respective thermal rate constants were calculated using variational transition-state theory including the contribution of tunneling.

A Theoretical Study of Brominated Porphycenes: Electronic Spectra and Intersystem Spin-Orbit Coupling.

In this paper, a time-dependent density functional theoretical study (TDDFT) has been carried out for brominated 2,7,12,17-tetra-n-propylporphycenes. Their potential therapeutic use in photodynamic therapy (PDT), a noninvasive medical treatment of cancer diseases, is due to the strong absorbance in the red part of the visible spectrum and the presence of heavy atoms (bromine). The prediction of electronic spectra for photosensitizer molecules can be a valuable tool in the design of drugs for application in PDT.

The inactivation of lipid peroxide radical by quercetin. A theoretical insight.

The effectiveness of naturally occurring antioxidant quercetin in the inactivation of the damaging lipid peroxide radical was investigated by means of hybrid density functional based approach, using the direct dynamics method, where the thermal rate constants were calculated using variational transition-state theory with multidimensional tunneling. H-atom abstraction in quercetin by CH(3)OO peroxide occurs preferentially at the 4'OH phenolic site, from both kinetic and thermodynamic points of view. In principle, the narrowness of the obtained adiabatic potential-energy profile makes the occurrence of a significant tunnelling contribution possible.

One-electron spin-orbit contribution by effective nuclear charges.

Effective nuclear charges of the main group elements from the second up to the fifth row have been developed for the one-electron part of the spin-orbit (SO) coupling Hamiltonian. These parameters, suitable to be used for SO calculations of large molecular systems, provide a useful and remarkably good approximation to the full SO Hamiltonian. We have derived atomic effective nuclear charges by fitting procedure.

Reaction mechanism of molybdoenzyme formate dehydrogenase.

Formate dehydrogenase is a molybdoenzyme of the anaerobic formate hydrogen lyase complex of the Escherichia coli microorganism that catalyzes the oxidation of formate to carbon dioxide. The two proposed mechanisms of reaction, which differ in the occurrence of a direct coordination or not of a SeCys residue to the molybdenum metal during catalysis were analyzed at the density functional level in both vacuum and protein environments. Some DF functionals, in addition to the very popular B3LYP one, were employed to compute barrier heights.