| Abstract: | The effect of temperature, concentration, external magnetic fields and paramagnetic quenchers on the lifetime of biradicals produced in the Norrish Type II reaction has been examined. Analysis of this data and that available from earlier reports leads to the conclusion that in addition to controlling the biradical lifetimes, intersystem crossing in triplet-derived biradicals plays a critical role in determining the behaviour and products which result from singlet biradical reactions. The effect is attributed to conformational memory in the singlet biradical which reflects its short lifetime. |
