Mechanism of an exceptional class of photostabilizers: A seam of conical intersection parallel to excited state intramolecular proton transfer (ESIPT) in o-hydroxyphenyl-(1,3,5)-triazine

Martin Paterson, M A Robb, L Blancafort, A D DeBellis

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

We present a detailed CASSCF study of the mechanism of excited-state intramolecular proton transfer (ESIPT) in the o-hydroxyphenyl triazine class of photostabilizers. The valence-bond analysis of the ground state and the two pi pi* excited states permits a simple chemical interpretation of the mechanistic information. Our results show that the barrier to enol-keto tautomerism on the ground-state adiabatic surface is high. Following photoexcitation to the charge-transfer state, the ESIPT is predicted to take place without a barrier. Radiationless decay to the ground state is associated with an extended seam of conical intersection, with a sloped topology lying parallel to the ESIPT path, which can be accessed at any point along the reaction path. Our results show that the triazine class of photostabilizers has the photochemical and photophysical qualities associated with exceptional photostability.

Original languageEnglish
Pages (from-to)7527-7537
Number of pages11
JournalJournal of Physical Chemistry A
Volume109
Issue number33
DOIs
Publication statusPublished - 25 Aug 2005

Keywords

  • ELECTRON-TRANSFER
  • UV ABSORBERS
  • BENZOTRIAZOLE
  • DEACTIVATION
  • STABILIZERS
  • MOLECULES
  • DECAY
  • BOND

Cite this