Even though lead is a well-known toxicant widely scattered throughout the world since antiquity, its chemistry is poorly documented at the molecular level. Here we investigate the hydration of the Pb2+ ion by means of first-principles molecular dynamics (Car–Parrinello molecular dynamics, CPMD). We found that the hydrated cation is heptacoordinated in a dynamically holodirected arrangement roughly corresponding to a fluxional distorted pentagonal bipyramid. The time-averaged PbO bond length is especially large and amounts to 2.70 Å with an associated root-mean-square deviation of 0.26 Å. This results from a dynamic exchange between short (<2.6 Å), intermediate (2.6–3.0 Å) and long (>3.0 Å) PbO bonds. The latter very long PbO distance implies that the determination of the coordination number nc from experimental work may not necessarily yield values directly comparable to the theoretical value of nc=7, since not all experimental techniques would recognize such a long distance as a bond to the metal cation. Pronounced disorders are evidenced in the second shell, characteristic of a chaotropic cation, and exchanges between the first and second shells cannot be excluded on a timescale of a few tens of picoseconds.
If you can't find a tool you're looking for, please click the link at the top of the page to "Go to old article view". Alternatively, view our Knowledge Base articles for additional help. Your feedback is important to us, so please let us know if you have comments or ideas for improvement.