Interplay of condensation and chelation in binary and ternary Th(iv) systems

Abstract

Th(IV) readily undergoes hydrolysis and condensation in aqueous solutions to form polynuclear molecular species and the system becomes increasingly complicated when organic chelators or other metals are present in solution, leading to the formation of complexes with vastly different structural topologies. Five compounds containing binary and ternary Th(IV) complexes have been synthesized and structurally characterized using single-crystal X-ray diffraction, including Na 4 [Th 6 O 2 (C 10 O 7 N 2 H 14) 6 ]·20.5H 2 O (Th 6 hedta), [Th(C 9 O 6 NH 12)(H 2 O)(NO 3)]·1.5H 2 O (Th(ntp)), [Th 2 Al 8 (OH) 14 (H 2 O) 12 (C 6 O 5 NH 8) 4 ](NO 3) 6 ·17.5H 2 O (Th 2 Al 8 heidi), (C 4 N 2 H 12) [Th 2 Fe 2 (OH) 2 (H 2 O) 2 (C 6 O 7 H 4) 2 (C 6 O 7 H 5) 2 ]·6H 2 O (Th 2 Fe 2 cit), (C 4 N 2 H 12) [ThFe 2 O(H 2 O) 3 (C 11 O 9 N 2 H 13) 2 ]·6H 2 O (ThFe 2 dhpta). Additional chemical characterization by infrared spectroscopy and thermogravimetric analysis provides information on the chelation by the organic ligands and thermal stability. These molecular complexes can be utilized to understand aqueous speciation in mixed-metal solutions and also provide information regarding contaminant adsorption on iron(III) and aluminum(III) oxide surfaces.