Photochemical reactions in doped fluorene single crystals involving hydrogen abstraction in different reaction geometries

Irreversible hydrogen abstraction reactions have been observed in dihydrophenazine doped single crystals of fluorene after photoexcitation of the guest molecules. Additional hydrogen abstraction from one fluorene host molecule in any of several inequivalent nearest‐neighbor sites leads to the production of stable phenazinyl–fluorenyl radical pairs in the triplet state. Their electron paramagnetic resonance spectra have been analyzed for the different reaction geometries. There are indications that the abstracted hydrogen atoms remain in the crystal as an integral part of the radical pair geometry.