Structural Demonstration of the Role of Ligand Framework Conformability in Copper(II)/Copper(I) Redox Potentials

Two macrocyclic CuN2S2 complexes are described. In the larger (16-membered) macrocycle, a butylene linkage allows the ligand to accommodate the pseudotetrahedral geometry of the copper(I) form, thus elevating the CuII/CuI E1/2 value in comparison with the 15-membered ring's complex. This is the first crystallographic demonstration of this flexibility factor.