• gold oxide;
  • oxidation state;
  • superhalogen;
  • complex compounds;
  • density functional theory

Theoretical density functional calculations are performed on AuOnq species for q = 0–3 and n = 1–4 in various spin states. AuOn species are found to be relatively more stable in their mono-anionic forms and behave as superhalogens for n ≥ 2. The maximum oxidation state of Au is found to be +7 in these species, but limited to +5. This fact is explained by considering interactions of AuOn superhalogens with K atom and which leads to the formation of more stable KAuOn complex up to n = 3, only. Thus, the present study is expected not only to motivate the synthesis of a new class of salts but also to assign the maximum oxidation state of gold. © 2013 Wiley Periodicals, Inc.