Encontrados 9 documentos, a visualizar página 1 de 1
A chemical understanding for the enhanced hydrogen tunnelling in hydroperoxidat...
Barroso, Mónica; Arnaut, Luís G.; Formosinho, Sebastião J.The reaction path of the Interacting-State Model (ISM) is used with the Transition-State Theory (TST) and the semiclassical correction for tunnelling (ISM/scTST) to calculate the rates of H-atom abstraction from C(11) of linoleic acid catalysed by soybean lipoxygenase-1 (SLO), as well as of an analogous uncatalysed reaction in solution. The calculated hydrogen-atom transfer rates, their temperature dependency a...
Absolute Rate Calculations. Proton Transfers in Solution
Barroso, Mónica; Arnaut, Luís G.; Formosinho, Sebastião J.The reaction path of the intersecting-state model is used in transition-state theory with the semiclassical correction for tunneling (ISM/scTST) to calculate the rates of proton-transfer reactions from hydrogen-bond energies, reaction energies, electrophilicity indices, bond lengths, and vibration frequencies of the reactive bonds. ISM/scTST calculations do not involve adjustable parameters. The calculated prot...
Tunnelling in low-temperature hydrogen-atom and proton transfers
Arnaut, Luís G.; Formosinho, Sebastião J.; Barroso, MónicaThe reaction path of the interacting-state model with the Lippincott-Schroeder potential for hydrogen bonds, is used in transition-state theory calculations with the semiclassical correction for tunnelling (LS-ISM/scTST) to estimate proton and hydrogen-atom transfer rates at low temperatures. Down to 100 K, the semiclassical correction leads to semi-empirical rates and isotope effects that are in good agreement...
Dramatic Pressure-Dependent Quenching Effects in Supercritical CO2 Assessed by ...
Barroso, Mónica; Chattopadhyay, Nitin; Klymchenko, Andrey S.; Demchenko, Alexander P.; Arnaut, Luís G.; Formosinho, Sebastião J.Steady-state fluorescence of 4‘-dimethylamino-3-hydroxyflavone (DMA3HF) was observed in supercritical carbon dioxide (scCO2). Excited-state intramolecular proton transfer (ESIPT) occurs resulting in two well-separated emission bands corresponding to the normal and tautomer forms. As the scCO2 density exceeds 0.7 g/mL, the relative intensity of the two bands tends to a constant value, comparable to that observed...
Absolute Rate Calculations: Atom and Proton Transfers in Hydrogen-Bonded Systems13
Barroso, Mónica; Arnaut, Luis G.; Formosinho, Sebastião J.We calculate energy barriers of atom- and proton-transfer reactions in hydrogen-bonded complexes in the gas phase. Our calculations do not involve adjustable parameters and are based on bond-dissociation energies, ionization potentials, electron affinities, bond lengths, and vibration frequencies of the reactive bonds. The calculated barriers are in agreement with experimental data and high-level ab initio calc...
Fluorescence from the second excited singlet state of 3-hydroxyflavone in super...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Arnaut, Luís G.; Formosinho, Sebastião J.Fluorescence from the second excited singlet state (S2) of 3-hydroxyflavone (3HF) has been observed for the first time in supercritical carbon dioxide (sc-CO2) environment. Steady-state experiments reveal that the intramolecular proton transfer is less effective from the S2 state of 3HF compared to that from the S1 state. ; http://www.sciencedirect.com/science/article/B6TFN-4BVP7G9-5/1/fe6fe6a663b47e1a622241...
Photophysics of 3-hydroxyflavone in supercritical CO2: a probe to study the mic...
Chattopadhyay, Nitin; Barroso, Mónica; Serpa, Carlos; Isilda Silva, M.; Arnaut, Luís G.; Formosinho, Sebastião J.The excitation of 3-hydroxyflavone (3HF) to its second excited singlet state (S2) gives rise to dual fluorescence in supercritical carbon dioxide. The ultraviolet fluorescence originated from the S2 state of 3HF is well separated from the green emission emanating from the tautomeric form, produced via the excited state intramolecular proton transfer. The relative intensity of the S2 to the tautomer fluorescence...
Absolute Rate Calculations for Atom Abstractions by Radicals: Energetic, Struc...
Arnaut, Luís G.; Pais, Alberto A. C. C.; Formosinho, Sebastião J.; Barroso, MonicaWe calculate transition-state energies of atom-transfer reactions from reaction energies, electrophilicity indices, bond lengths, and vibration frequencies of the reactive bonds. Our calculations do not involve adjustable parameters and uncover new patterns of reactivity. The generality of our model is demonstrated comparing the vibrationally adiabatic barriers obtained for 100 hydrogen-atom transfers with the ...
Intersecting-state model calculations on fast and ultrafast excited-state proto...
Barroso, Mónica; Arnaut, Luís G.; Formosinho, Sebastião J.The intersecting-state model (ISM) is applied to the calculation of absolute rate constants for proton-transfer reactions of naphthols and substituted naphthols in the first singlet state and for ground states. ISM incorporates quantum-mechanical tunnelling, zero-point energy corrections and an electrophilicity parameter to account for the lowering of the binding energy of transition states. Good agreement with...
| Financiadores do RCAAP | |||||||
|
|
|
|
|
|
||