SPIN INVERSION IN THE 1,4-DIRADICAL DERIVED FROM 2,4,6-TRIISOPROPYLBENZOPHENONE: IMPORTANCE OF LONE-PAIR ORBITAL ROTATION.

Article abstract of DOI:10.1021/ja00354a010

,6-Diisopropyl-2,2-dimethyl-1-phenyl-1,2-dihydrobenzocyclobuten-1-ol (2) was submitted to direct (254 nm) and sensitized photolysis and thermolysis in the absence or presence of oxygen. Direct photolysis (313 nm) of 2,4,6-triisopropylbenzophenone (1) was also performed in the absence or presence of oxygen. Interconversion between 1 and 2 and production of 1,3-diisopropyl-10,10-dimethylanthrone (3) and ,4-dihydro-1-hydroxy-6,8-diisopropyl-4,4-dimethyl-1-phenyl-2,3-benzo dioxin (4) happened in various quantum yields depending upon the reaction conditons. It is concluded that DR, which is generated from the direct photolysis of 1, is spin protected and its lifetime is determined by the rate of intersystem crossing.