σ and π Effects on the copper(II)/copper(I) redox couple potential in tetraazamacrocyclic complexes

The electrochem. redn. was studied of Cu(II) complexes with 14 membered tetraaza macrocycles with different structural features and different degrees of unsatn. Each complex undergoes a reversible 1-electron redn. at the Hg electrode in MeOH contg. 0.1 M Et4NBF4. The Cu(II)/Cu(I) process in macrocycles systems can be promoted through modification of the ligands that (a) reduce its σ-donor ability by destabilizing Cu(II) and (b) increase its π-acceptor properties by stabilizing Cu(I). Geometrical effects favorable to formation of Cu(I) can be induced in a fixed coplanar array of 4 N atoms by rearranging the system of fused chelate rings.