X-ray photoelectron spectroscopy of copper(II), copper(I), and mixed valence systems

✍ Scribed by Heinz Rupp; Ulrich Weser

• Publisher: Elsevier Science
• Year: 1976
• Weight: 985 KB
• Volume: 6
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(00)80049-6

✦ Synopsis

X-ray photoelectron spectroscopy using copper( copper(I) and the mixed valence Cu(II)/Cu(i) compounds was empIoyed as a means of studying electron transfer reactions in copper proteins_ The X-ray photoelectron spectra of copper(i1) compounds display characteristic satellites of both variable sire and resolution. Some of these satellites could be assigned to specific @and interactions. Unlike electron paramagnetic resonance spectroscopy, the X-ray photoelectron spectroscopic measurements of copper(I) Lumpounds allowed the unequivocai assignment of this oxidation state. No satelhtes at alI could be detected in the Cu(I) spectra. Furthermore, established mixed valence Cu(II)/Cu(I) complexes including Cu2S0, -CuSO, -2H=O and C&Cl, (ethylenediimine)z proved essentially a mixture of distinct portions of Cu(1) and Cu(II)_ This indicates that both oxidation states of copper survive in such complexes. In contrast, all Cu X-ray photoelectron signals of the more tentatively described mixed valence complexes NalCu,S, and the mineral covellite, CuI, CuU 2 (S,), S,, could be attributed exclusively to Cu(I)_ In view of the known binding of copper with sulfur in many copper proteins, it was of utmost importance to study the copper-sulfur interactions_ We have demonstrated the absence of Cu(II) in CM. This indicates strong metal-induced polarization of sulfur resulting in electron transfer to copper to yield Cu(1).