A theory ofnonverticaltriplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π* triplet donors to 1,3,5,7-cyclooctatetraene
| Autor: | A. Ulises Acuña, Jose L. Andres, Obis Castaño, Manuela Merchán, Luis Manuel Frutos |
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| Rok vydání: | 2004 |
| Předmět: |
Arrhenius equation
General Physics and Astronomy Triplet state Molecular configurations Acceptor Potential energy Ground states UNESCO::FÍSICA::Química física Cyclooctatetraene chemistry.chemical_compound symbols.namesake Transition state theory Organic compounds Potential energy surfaces chemistry symbols Molecule Physics::Chemical Physics Physical and Theoretical Chemistry Atomic physics FÍSICA::Química física [UNESCO] Adiabatic process |
| Zdroj: | A theory of nonvertical triplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π∗ triplet donors to 1,3,5,7-cyclooctatetraene RODERIC. Repositorio Institucional de la Universitat de Valéncia instname |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.1631418 |
| Popis: | Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of "nonvertical" behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion parameter gamma=(2g(2)/kappa(1))(1/2) in which g stands for the norm of the energy gradient in the PES of the acceptor triplet state and kappa(1) is a combination of vibrational force constants of the ground-state acceptor in the gradient direction. The application of the model to existing experimental data for the triplet energy transfer reaction to COT from a series of pi,pi(*) triplet donors, provides a detailed interpretation of the parameters that determine the transfer rate constant. In addition, the model shows that the observed decrease of the acceptor electronic excitation energy is due to thermal activation of C=C bond stretchings and C-C bond torsions, which collectively change the ground-state COT bent conformation (D(2d)) toward a planar triplet state (D(8h)). |
| Databáze: | OpenAIRE |
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