title: New insights into the by-product fatigue mechanism of the photo-induced ring-opening in diarylethenes.
abstract: The photochromic properties of diarylethenes, some of the most studied class of molecular switches, are known to be controlled by non-adiabatic decay at a conical intersection seam. Nevertheless, as their fatigue-reaction mechanism - leading to non-photochromic products - is yet to be understood, we investigate the photo-chemical formation of the so-called by-product isomer using three complementary computational methods (MMVB, CASSCF and CASPT2) on three model systems of increasing complexity. We show that for the ring-opening reaction a transition state on S1(2A) involving bond breaking of the penta-ring leads to a low energy S1(2A)/S0(1A) conical intersection seam, which lies above one of the transition states leading to the by-product isomer on the ground state. Therefore, radiationless decay and subsequent side-product formation can take place explaining the photo-degradation responsible for the by-product generation in diarylethene-type molecules. The effect of dynamic electron correlation and the possible role of inter-system crossing along the penta-ring opening coordinate are discussed as well.
authors: Chimie Et Interdisciplinarité, Synthèse, Analyse, Modélisation (CEISAM), UMR CNRS no. 6230, BP 92208, Université de Nantes, 2, Rue de la Houssinière, 44322 Nantes, Cedex 3, France. denis.jacquemin@univ-nantes.fr david.mendive@univ-nantes.fr.
authors: David
authors: D
authors: Mendive-Tapia
authors: Aurélie
authors: A
authors: Perrier
authors: Michael J
authors: MJ
authors: Bearpark
authors: Michael A
authors: MA
authors: Robb
authors: Benjamin
authors: B
authors: Lasorne
authors: Denis
authors: D
authors: Jacquemin