The rhodizonate anion, C6O62-, is the six-carbon member of a family of cyclical compounds known as oxocarbons. The most well-known application of rhodizonate is as a colorimetric test for Pb. The sodium rhodizonate test for Pb is a well-documented forensic test for determination of trace Pb(II) presence from firearm discharge, yet the details behind the coordination chemistry involved in this test, and the chemical explanation of the observed color changes are largely unknown. Our group has recently investigated the Pb(II) coordination chemistry of rhodizonate and we are now expanding toward structural and spectroscopic characterization of the complexes involved in the sodium rhodizonate test, in a variety of buffer conditions. Furthermore, rhodizonate has been shown to coordinate with a variety of transition metal cations, as well as to uranyl (UO22+) cations. Considering the importance of separating minor actinides from spent nuclear fuel and for use in environmental cleanup of radioisotopes, rhodizonate could potentially be a new ligand framework for addressing problems in nuclear processing. Using lanthanides as surrogates for actinides, we have shown by UV-Vis Spectroscopy and applying the Job Plot method that rhodizonate exhibits a variety of complexation ratios when coordinated to different lanthanides. Specifically, we have shown that rhodizonate coordinates with Sm(III), Gd(III) and Nd(III) in a 1:1 ratio, but with a 2:1 ratio for Ce(III), and a 1:2 ratio for Y(III). Using FT-IR spectroscopy, mass spectrometry, and X-ray crystallography, the coordination chemistry of rhodizonates with lanthanides will be further investigated.

Coordination chemistry of the rhodizonate anion with Pb(II) and lanthanides: From understanding complexation to analytical applications

253rd National Meeting (2017)

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