Anomalous chemical shifts in X-ray photoelectron spectra of sulfur-containing compounds of silver (I) and (II)

• Published in: Journal of electron spectroscopy and related phenomena Vol. 202; pp. 38 - 45
• Main Authors: Grzelak, A., Jaroń, T., Mazej, Z., Michałowski, T., Szarek, P., Grochala, W.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2015
• Subjects: High oxidation state; Oxidizer; Silver; Sulfur; XPS; Silver; XPS; Oxidizer; Sulfur; High oxidation state
• ISSN: 0368-2048; 1873-2526
• DOI: 10.1016/j.elspec.2015.02.013

•Ag 3d5/2 binding energy for Ag(II)SO4 is as large as 370.1eV.•This is the largest value ever measured for a silver (II) compound.•Large shift is connected with the extreme oxidizing nature of Ag(II) species.•Ag(I)2S2O7 exhibits both positive and negative shifts with respect to metallic Ag.•Two distinct Ag(I) sites are responsible for large BE difference of 3.6eV.
Anomalous chemical shifts, i.e. cases when binding energy decreases with the increase of the oxidation state, have been well-documented for selected compounds of silver, and well understood based on analysis of initial- and final-state effects in the XPS spectra. Here we report two examples of even more exotic behaviour of chemical shifts for two silver compounds. The first one is Ag2S2O7 which exhibits both positive and negative substantial shifts with respect to metallic Ag for two distinct Ag(I) sites in its crystal structure, which differ by as much as 3.6eV. Another is AgSO4, a rare example of oxo silver (II) salt, which exhibits “normal” chemical shift but the Ag 3d5/2 binding energy takes the largest value measured for a silver (II) compound (370.1eV). This property is connected predominantly with the extremely strongly oxidizing nature of Ag(II) species.