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Breaking the Kasha Rule for More Efficient Photochemistry

This paper provides a systematic review and analysis of different phenomena that violate a basic principle, Kasha’s rule, when applied to photochemical reactions. In contrast to the classical route of ultrafast transition to the lowest energy excited state and photochemical reaction starting therein, in some cases, these reactions proceed directly from high-energy excited states. Nowadays, this phenomenon can be observed for a number of major types of excited-state reactions: harvesting product via intersystem crossing; photoisomerizations; bond-breaking; and electron, proton, and energy transfers. We show that specific conditions for their observation are determined by kinetic factors. They should be among the fastest reactions in studied systems, competing with vibrational relaxation and radiative or nonradiative processes occurring in upper excited states. The anti-Kasha effects, which provide an important element that sheds light on the mechanisms of excited-state transformations, open new possibiliti...

Authors:   Alexander P. Demchenko; Vladimir I. Tomin; Pi-Tai Chou
Journal:   Chemical Reviews
Year:   2017
DOI:   10.1021/acs.chemrev.7b00110
Publication date:   09-Oct-2017
Facts, background information, dossiers
  • excited states
  • Energy
  • relaxation
More about American Chemical Society Publications
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