The molecular structure of aqueous Hg(II)-EDTA as determined by X-ray absorption spectroscopy

The widespread presence and persistence of ethylenediaminetetraacetic acid (EDTA) in aquatic environments can lead to the formation of metal-EDTA complexes that influence metal bioavailability and mobility. Recently, the Hg(II)-EDTA complex was observed to slightly promote the biouptake of Hg(II) to the bacterium Escherichia coli and to undergo a relatively quick ligand exchange reaction with thiols at the bacterial cell membrane. The reactivity of a metal complex depends on its molecular structure; however, the molecular structure of aqueous Hg(II)-EDTA has yet to be reported. Here, we use X-ray absorption spectroscopy to determine the molecular structure of aqueous Hg(II)-EDTA. Our results suggest that aqueous Hg(II)-EDTA displays distorted octahedral geometry with one water molecule in the coordination sphere.