Molecular machines based on metal ion translocation

Transition metal ions can be moved reversibly between the two coordinativel y unequivalent compartments A and B of a ditopic ligand, using as an input the variation of a bulk solution parameter, either pH or redox potential. I n a redox-driven translocation, the metal moves reversibly from A to B on c ycling between two consecutive oxidation states (e.g., Cu-II/Cu-I; Fe-III/F e-II) by means of auxiliary oxidation and reduction reactions. In a pH-driv en process, one compartment displays also acid-base properties (AH,, c A(n- ) + nH(+)), and the Mn+ ion is translocated between B and A(n-) through con secutive addition of base and acid.