The photochemical properties of derivatives of 10-methylacridinium ion that have been modified by substitution with anilide moieties (e.g., -C6H4NHCO-) at the 9-position have been examined. Intramolecular electron transfer involving the anilide group as electron donor and the acridinium ring as electron acceptor was verified by observation of the quenching of fluorescence associated with the local acridinium chromophore and by the recording of electron transfer phototransient spectra in the picosecond time domain. The amidobiphenyl linkage was a superior electron donor and displayed rapid forward and reverse photoinduced electron transfer with rate constants for the latter reaching 5.2 x 10(11) s(-1) (CH3CN solvent).