X-ray-Induced Photoreduction of Hg(II) in Aqueous Frozen Solution Yields Nearly Monatomic Hg(0).

We use X-ray-induced photochemistry, which is well known to cause changes in a number of systems, to reduce Hg(II) to Hg(0) in frozen aqueous solution with added glycerol maintained at 10 K. X-ray absorption spectroscopy was used to monitor the extent of the reaction and to characterize the species. An analysis of the extended X-ray absorption fine structure (EXAFS) of the photochemical product indicated a nearly monatomic Hg(0) species bound only by long, weak bonds to oxygens at ∼3.5 Å. The results of the EXAFS analysis agree quantitatively with the results of density functional theory calculations using the meta-GGA approximation with the M11-L functional. This is the first structural characterization of nearly monatomic Hg(0) bound by hard ligands similar to those expected in aqueous environmental systems. We conclude that Hg(0) is expected to exist in solution as a nearly monatomic entity.