Photoinduced electron transfer (PET) bond cleavage reactions

Abstract

The primary objective of this chapter is to provide a review of the topic of photochemically stimulated electron transfer bond cleavage reactions for approximately the past ten years. PET stimulated bond cleavage reactions are an important way to initiate radical and/or ionic chemistry that can be used in synthesis, imaging, photocuring, and photoresist chemistry. Several inter- and intramolecular photochemical single electron transfer (SET) induced bond cleavage reactions will be reviewed which result from either one-electron oxidation or one-electron reduction. A discussion of onium salt systems that undergo bond cleavage as a direct result of photochemical excitation of an electron from a π highest occupied molecular orbital (HOMO) to a σ* lowest unoccupied molecular orbital (LUMO) will also be provided. Examples of intramolecular rearrangement in, for example, aryldialkylsulfonium salts systems are also discussed. Although, most photochemical SET bond cleavage reactions occur in a stepwise manner through an ion-radical intermediate, if the initial substrate is uncharged, future trends in this field involve the use of concerted bond cleavage processes to eliminate energy wasting back electron transfer.