Stabilities and Redox Properties of Cu(I) and Cu(II) Complexes with Macrocyclic Ligands Containing the N2S2 donor Set

✍ Scribed by Karappulli P. Balakrishnan; Thomas A. Kaden; Liselotte Siegfried; Andreas D. Zuberbühler

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: German
• Weight: 600 KB
• Volume: 67
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19840670419

✦ Synopsis

Abstract

The complexation of Cu(I) and Cu(II) by a series of 12‐, 14‐ and 16‐membered macrocyclic ligands 1–6 containing the N~2~S~2~ donor set has been studied potentiometrically, spectrophotometrically and voltammetrically.

In the case of Cu(II), mononuclear complexes CuL^2+^ with stability constants of 10^10^–10^15^ are formed. In addition, partially hydrolyzed species Cu(L)OH^+^ are observed at pH > 10 for the 12‐membered ligands. For Cu(I), beside the specis CuL^+^ with stabilities of 10^12^–10^14^, the unexpected formation of protonated species CuLH^2+^ was detected. In contrast to the well‐known general trends in coordination chemistry, the stability of these protonated species increases relative to that of the complexes with the neutral ligand when the ring size and concomitantly the distance between neighbouring donor atoms is decreased. From the stability constants of the Cu(I)‐ and Cu(II)‐complexes the redox potentials have been calculated and are compared to the values of E^1/2^ obtained by cyclic voltammetry. Despite the identical donor set the Cu(II)/Cu(I) redox potentials of the complexes are spanning a range of 340 mV or six orders of magnitude in relative stability, reflecting the importance of subtle differences in steric requirements.