The wavelength-dependent photochemistry of the endoperoxide of 1,4,9,10-tetraphenylanthracene: indirect evidence for the existence of several reaction channels leading to cycloreversion
1983; Elsevier BV; Volume: 23; Issue: 3 Linguagem: Inglês
10.1016/0047-2670(83)87010-5
ISSN1873-2658
Autores Tópico(s)Organic Chemistry Cycloaddition Reactions
ResumoThe wavelength dependence of the quantum yield Q1 for the cycloreversion of the endoperoxide of 1,4,9,10-tetraphenylanthracene (TPAPO) reveals that this reaction originates from the thermalized S2 state, which is also the case for other anthracene endoperoxides. However, a second increase in Q1 with decreasing wavelength is observed for an endoperoxide for the first time. This surprising result indicates the existence of several thermally equilibrated upper singlet states Sn (n ⩾ 2) leading to cycloreversion. A comparison of the Q1 values for TPAPO and other related endoperoxides demonstrates that its magnitude for these compounds is determined essentially by internal conversion and hence by the energy gap S2 S1. The quantum yield Qdec for the rearrangement of TPAPO was also determined. The influence on Qdec of the type and position of the substituents on the anthracene moiety is discussed.
Referência(s)