The origin of the photochromic properties of diarylethenes is a conical intersection (which we have located computationally), but we show that dynamics calculations are necessary to explain why the conical intersection is accessible, because the excited-state reaction path is not contained in the branching space defining the intersection. Four different systems have been studied: 1,2-di(3-furyl)ethene, 1,2-di(3-thienyl)ethene, 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, and a model hydrocarbon system. Critical points on the ground- and excited-state potential energy surfaces were calculated using complete active space self-consistent field (CASSCF) theory; dynamics calculations were carried out using the molecular mechanics-valence bond (MMVB) method. The main experimental observations (i.e., picosecond time domain, quantum yield, temperature dependence, and fluorescence) can be interpreted on the basis of our results.
Can Diarylethene Photochromism Be Explained by a Reaction Path Alone? A CASSCF Study with Model MMVB Dynamics
RAVAGLIA, Marcella;
2003
Abstract
The origin of the photochromic properties of diarylethenes is a conical intersection (which we have located computationally), but we show that dynamics calculations are necessary to explain why the conical intersection is accessible, because the excited-state reaction path is not contained in the branching space defining the intersection. Four different systems have been studied: 1,2-di(3-furyl)ethene, 1,2-di(3-thienyl)ethene, 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene, and a model hydrocarbon system. Critical points on the ground- and excited-state potential energy surfaces were calculated using complete active space self-consistent field (CASSCF) theory; dynamics calculations were carried out using the molecular mechanics-valence bond (MMVB) method. The main experimental observations (i.e., picosecond time domain, quantum yield, temperature dependence, and fluorescence) can be interpreted on the basis of our results.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
