BONDING IN SILVER-OXYGEN COMPOUNDS FROM AG-L3 XANES SPECTROSCOPY

Compounds containing cations with a valence electron configuration that can formally be described as (n-1)d10ns0 (Cu+, Ag+, Au+, Hg2+) exhibit a variety of unusual structural properties, e.g. low coordination numbers and short cation-cation distances. The incorporation of d electrons from the closed d10 sub-shell has been debated for a long time as a reason for this extraordinary behaviour. Ag L3 XANES spectra of oxidic silver(I) compounds exhibit a prominent peak at the rising edge. By comparison with the XANES spectrum of a Ag(III) periodate complex this peak is assigned to a transition from initial 2p states to 4d final states, proving that in oxidic Ag(I) compounds the closed-shell configuration 4d10 is broken. The intensity of the peak signalling unoccupied 4d states is related to the degree of covalent bonding in a compound.