Abstract

Intersystem crossing plays a critical role in defining the intramolecular dynamics of aromatic carbenes and thereby directly affects their spin state dependent chemistry. For example, the chemistry of diphenylcarbene (DPC) depends on the rapid thermal equilibration which takes place between its ground state and its low-lying singlet state (eqn. 1). In fluid solution, at room temperature, the singlet to triplet conversion step has been found to proceed at a rate on the order of 10¹⁰S⁻¹, while the reverse triplet to singlet conversion step is roughly three orders of magnitude slower. Beyond this information little is actually known about the intersystem crossing rates associated with the carbene system. The problem of. characterizing the factors which include both intermolecular and intramolecular effects on the intersystem crossing dynamics of the carbene reamains an outstanding issue. In particular, an extremely important question is the extent to which the environment can affect the intramolecular spin conversion dynamics of the carbene. At this conference we wish to report on the role of the solvent and in particular the observation of a novel solvent polarity effect on the singlet to triplet intersystem crossing rate (k_ST) in arylcarbenes.

© 1984 Optical Society of America