Synthesis and evaluation of ¹⁰⁵Rhodium (III) complexes of phosphine chelate systems

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] ¹⁰⁵Rh has attractive nuclear and chemical properties to be investigated as a nuclide for development of potential radiopharmaceuticals. ¹⁰⁵Rh decays by [beta]- emission, 0.566 MeV (75%) and 0.248 MeV (19.7%), with an associated [gamma] emission of 0.319 MeV (19%), and a half-life of 35.4 hours. Complexes of Rh(III) are kinetically inert with respect to ligand exchange. ¹⁰⁵Rh is produced by neutron irradiation of an enriched ¹⁰⁴Ru (99.21%) target at the University of Missouri Research Reactor (MURR) in high specific activity, by separation from the target material. Chelate systems comprised of tertiary phosphines may serve as internal reducing agents, thus limiting the amount of ethanol and decreasing the temperatures required for labeling ¹⁰⁵Rh. The chelate systems PS₂, P₂N₂, and P₂S₂ have been investigated for use as bifunctional chelates (BFCAs). Ligands were synthesized and evaluated as potential chelates for ¹⁰⁵Rh. Labeling was investigated using both [superscript-nat]Rh as well as ¹⁰⁵Rh produced at MURR. These systems focus on differences in chelating atoms and hydrophobicity as methods for optimization of labeling conditions for ¹⁰⁵Rh.