The intracluster proton transfer in aniline-amine complex ions is investigated by infrared photodissociation spectroscopy and density functional theory calculations. The proton acceptors include ammonia, methylamine, dimethylamine and trimethylamine in ascending order of proton affinity. The spectra of (aniline-ammonia)- and (aniline-methylamine)(+) demonstrate the persistence of the aniline ion unit in the complexes. For (aniline-dimethylamine)- and (aniline-trimethylamine)-, the spectra imply the transformation to the anilino radical (C6H5NH) unit, suggesting the occurrence of the proton transfer. (C) 2002 Published by Elsevier Science B.V.