Both trimethylaminomethylferrocene (TMAFc(+)) and the corresponding ferrocenium species can be encapsulated by calix[6]arene-p-sulfonate in water as solvent. Selective encapsulation of the TMAFc(2+) form provides a basis for electrostatic acceleration of the TMAFc(2+/+) self-exchange kinetics. Encapsulation of both redox forms by the anionic host, however, eliminates the reactivity enhancement effect. [GRAPHICS] ucture of this homoleptic dication is square pyramidal rather than the classically expected trigonal bipyramid.4톈??