The intermolecular reactivities of amino-substituted perchlorotriphenylmethyl radicals 1−3 werestudied, with particular emphasis on electron transfer (ET) reactions. The natural fluorescencelifetimes and the rates of the electron-transfer quenching were studied with several electron donorsand acceptors. Fluorescence quenching studies demonstrate the importance of the redox potentialsof the ET pair on the observed steric and electronic properties.