Metal complexes with macrocyclic ligands. Part XIX. Synthesis and Cu2+‐complexes of a series of 12‐, 14‐ and 16‐membered cis‐ and trans‐N2S2‐macrocycles

A series of 12‐, 14‐, and 16‐membered N2S2‐macrocycles (9–11 and 19–21) with cis and trans‐arrangement of the heteroatoms have been synthesized by high‐dilution cyclization and subsequent reduction of the amides with B2H6. With these ligands the corresponding Cu2+‐complexes were prepared and their UV/VIS spectra, their electrochemistry and their EPR properties have been studied. Generally three absorption bands at 270–320 nm, 330–370 nm and 530–620 nm can be observed in aqueous solution and these have been assigned to the N→Cu2+ and S→Cu2+ charge‐transfer bands and to the d‐d* transition, respectively. The cyclic voltammetry in CH3CN shows in all cases a reversible or quasi‐reversible Cu2+/Cu+‐transition at potentials of 10–480 mV against SHE. The values of g‖ and A‖ obtained from EPR spectra indicate that the geometry of the Cu2+‐complex of the 14‐membered cis‐N2S2‐macrocycle is less distorted than that of the other complexes.