Photohomolysis and Photoionization of Substituted Tetraphenylethanes and C-C Fragmentation of 1,1,2,2-Tetra(p-R-phenyl)ethane Radical Cations (R=H, CH3, OCH3, Cl)

Two parallel reactions occur on photolysis of a series of tetraphenylethanes in 2,2,2-trifluoroethanol (below): one-photon homolysis of the central C–C bond yields the corresponding substituted diphenylmethyl radicals, but under conditions of high photon fluxes, biphotonic photoionization produces a radical cation, which subsequently undergoes efficient C–C scission of the aliphatic central bond to yield the radical and carbocation fragments.