Intramolecular energy transfer in rigid model compounds. Triplet transfer from cyclopentenone to spiro-linked fluorene

Abstract

The photochemical rearrangement of a spirocyclopropane-fluorene to a dibenzofulvene was used to determine the transfer efficiency from cyclopentenone to spiro-linked fluorene in an inflexible model compound in which the donor and the acceptor are connected to a norbornane frame. The quantum yield under direct fluorene excitation was compared with that obtained on selective n→π* excitation of the cyclopentenone donor. The results show that efficient partial transfer of energy takes place from the spectroscopic triplet level of the ketone to the T₁ state of the acceptor. The identity of the excited states and the kinetics of the overall energy migration process are discussed.