Monday, March 24, 2014

Surprising Article about Californium Chemistry

I just saw an interesting article from the RSC at Chemistry World based on this article in Nature Chemistry about the chemistry of californium. Researchers at Florida State University were supplied by the U.S. Department of Energy with several milligrams of 249Cf which was reported as being worth over a million dollars(!). They proceeded to synthesize a californium borate compound and they report on their experimental findings and electronic structure explanations of said findings.

The authors claim that "...there are, in fact, few parallels between lanthanide and actinide chemistry." The article continues that actinide chemistry (or californium-highly polarizable ligand chemistry, at any rate) in many respects is actually more similar to d-block behavior than expected f-block behavior.

What was particularly interesting was that the f-orbitals where also involved in bonding. The original article in Nature Chemistry discusses some DFT calculations on the californium borate, using a "60-electron core quasi-relativistic pseudopotential" for the californium. As far as I can tell, the authors where primarily concerned with scalar relativistic effects (i.e. s- and p-shell contraction and d- and f-shell expansion) rather than spin-orbit coupling. If so, the explanation for their results should be that the higher degree of s-orbital contraction in the actinides versus the lanthanides results in substantially larger f-orbitals, which are better able to form covalent bonds.

In any event, this article opens some interesting questions about heavy element chemistry, and I'm excited to seeing where it will lead.