Computational Calculations on Novel Plutonium Sequestering Agents

The use of actinides such as Pu in energy and weapons production has resulted in major environmental and health concerns. Chelation therapy is the approach currently used to treat actinide poisoning.  In order to effectively respond and treat actinide poisoning on a massive scale it is crucial to have access to effective, nontoxic chelating agents that can be orally administered, that are easily produced and safely stored. Specific sequestering agents have been designed and synthesized to bind actinides. Our study focuses on determining the structures and molecular properties of four hydroxypyridinone (HOPO)-based sequestering agents (2,2-Dime-3LI(1,2-HOPO), 3LI-(1,2-HOPO), 4LI(1,2-HOPO) and 5LI(1,2-HOPO) which have been shown to strongly and specifically bind plutonium at physiological pH. Our calculations were performed using density functional theory (DFT) with the B3LYP functional applied in conjunction with three basis sets (3-21G, 6-31G, and 6-311G) to obtain the equilibrium geometries, vibrational frequencies, and IR spectra for the ligands. The highest occupied molecular orbital (HOMO) – lowest occupied molecular orbital (LUMO) energy gap values for all compounds are greater than 4 eV suggesting that the ligands are chemically stable.  The ligands exhibit two hydrogen bonds which we suspect contribute to their chemical stability. The compounds exhibit dipole moments ranging between 3 to 4 Debye indicating they possess polar character.  Our computed vibrational frequencies were found in excellent agreement with the experimental values, suggesting our proposed models are good representations of the actual molecular structures.