Stabilities and Structures of Cu(II) Complexes with Linear Pentadentate Ligands by EPR Spectroscopy

✍ Scribed by Harald Gampp

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: German
• Weight: 656 KB
• Volume: 67
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19840670817

✦ Synopsis

Abstract

The pH‐dependent equilibria between Cu(II) and the potentially pentadentate ligands 4,7,10‐triazatridecane‐1,13‐diamine (1) and 1,9bis(2‐hydroxyphenyl)‐2,5,8‐triazanonane (2) have been studied in aq. solution at 298 K by EPR titration. Each ligand forms complexes CuLH~x~ (x=1,2,3) with strongly overlapping spectra. By using a recently developed algorithm, which does not need nay information with regard to the spectra of the species, stability constants and spectra were calculated from the EPR titration data. The anisotropic EPR spectra of the complexes were measured at 153 K and display axial or nearly axial symmetry (g∥ > g⊥) in each case. Based on the spectral parameters the assignment of the structures of the complexes was possible. With 1 and 2 the protonated complexes are equatorially coordinated, whereas in the fully deprotonated complexes an additional axial interaction occurs which is stronger with 2 than with 1.

The results of this study show that EPR spectroscopy is a useful method for investigating equilibrium systems of Cu^2+^ even in complicated cases where minor species occur and where the individual spectra are unknown and strongly overlapping.