The Role of Intersystem Crossing Steps in Singlet Oxygen Chemistry and Photo-oxidations

Atict-Singlet oxygen chemistry and photo-oxidation reactions, in general, often require one or more critical reaction steps that involve an intersystem crossing from a singlet state to a triplet state or vice versa. This paper considers two important intersystem crossing mechanisms, electron spin+lectron orbit (spinorbit) coupling and electron spin-nuclear spin (spin-spin) coupling, and how they may be involved : (1) in the deactivation of ‘0, lo 30, ; (2) in the thermal catalytic conversion of ‘0, to IO2 ; and (3) in the fragmentation of aromatic endoperoxides to yield 0, and an aromatic substrate.