Ditopic receptors for transition-metal ions: a heterobimetallic nickel(II)-copper(II) bis(macrocyclic) complex and its stepwise oxidation to the tervalent state

Ditopc ligand I was prepd. by B2H4-redn. of the parent bisdioxocyclam. I reacted successively with Ni(NO3)2 and Cu(NO3)2 to give Ni2L(ClO4)4, Cu2L(ClO4)4, and CuNiL(ClO4)4, sepd. by ion-exchange chromatog. CuNiL(ClO4)4 is electrochem. oxidized stepwise; the 1st step is the Ni(II)/Ni(III) oxidn. and the 2nd step is the 1-electron oxidn. of the Cu(II) center. Cu2L(ClO4)4 and Ni2L(ClO4)4 also exhibit 2-electron oxidn. behavior.