PNNL

Abstract

ESI of 1:1 mixtures of Th(ClO4)4 and ligand TMOGA in acetonitrile resulted in the observation of the TMOGA supported tetracation, Th(L)34?, in the gas phase. Three TMOGA ligands are necessary to stabilize the tetrapositive thorium ion; no Th(L)24? or Th(L)44? was observed. Theoretical calculations reveal that the Th(L)34? complex possesses C3 symmetry with the thorium center coordinated by nine oxygen atoms from three ligands, which forms a twisted TPP geometry. Actinide compounds with such a geometry feature a nine-coordinate chiral actinide center. The Th-L binding energy and bond orders of Th(L)n4? decrease as the coordination number increases, consistent with the trend of concurrently increasing Th-O distances. The Th-O bonding is mainly electrostatic in nature, but the covalent interactions are not negligible. CID of the Th(L)34? complex mainly resulted in charge reduction to form Th(L)2(L-86)³?oss of neutral TMOGA was not observed. The protic ligand methanol stabilized only tri- and dications of ligated thorium. The intensity of the Th(L)34? peak was reduced as the percentage of water increased in the Th(ClO4)4/TMOGA solution.