Substituent effects in the electrochemical behaviour of some mixed-ligand copper(II) chelates containing β-ketoenols and 1,2-diamines

✍ Scribed by Chris Tsiamis; Panos D. Jannakoudakis; Niki Sachsinger; Horst Hennig

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 779 KB
• Volume: 38
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(93)80161-r

✦ Synopsis

The electrochemical behaviour of a series of bis(Bdionato)copper((II) compounds, Cu(/L dionato), and mixed-ligand cationic chelates containing N,Ndiiethyl-N-ethyl-1,2diaminoethane, [Cu@-dionato)dmeen]', was investigated in diiethylsulphoxide solutions at carbon fibre electrodes in the presence of 0.1 mol dme3 NaNO, at 25°C. Two cathodic peaks are observed and the irreversibility of the second is due to the instability and decomposition of the reduced species. The one-electron reduction potentials and the reversibility of the heterogeneous electron transfer depends on the substituents within the /3dionato moiety. Despite the strong influence of the substituents, the linear correlation with the ionization energies of the Cu(Bdionato), chelates suggest that the electron transfer processes are associated with the singly occupied molecular orbital which is essentially localized on the copper(H) ion. The interdependence of the El,* values on the pK, of the j?-ketoenols and the Hammett D functions of the substituents indicates that inner-sphere electronic effects are operative even when other ligands are present.