Triplet Energy Transfer Photocatalysis: Unlocking the Next Level

Energy transfer can leverage the enormous potential of excited-state reactivity. Through indirect excitation'' of substrates, otherwise elusive reactivitymodes can be switched on, allowing for, e.g., cycloadditions, fragmentations, rearrangements, or challenging organometallic steps. This perspective recaps almost 70 years of energy transfer in organic chemistry, highlighting the way it evolved, as well as recent developments in the field of visible-light photocatalysis. Building upon the photophysical fundamentals, diverse applications and directions of energy transfer catalysis are pointed out.