Influence of the platform in multicoordinate ligands for actinide partitioning

Multicoordinate ligands based on the trityl, C-pivot, and CTV platforms and the ligating groups CMPO, DGA, PICO, and MPMA were synthesized and studied for their extraction properties. The extraction efficiencies of these multicoordinate ligands are largely influenced by the properties of the platform. The DAm values follow the order CTV6 > trityl ≈ C-pivot > CTV3 > CTV0 with a maximum for CTV6CMPO of DAm = 30 (SAm/Eu = 1.4, cL = 10–4 M, 3 M HNO3). There is a strong relationship between the DAm values, increasing in the order of CTV0CMPO < CTV3CMPO < CTV6CMPO, and the ‘mobility’ of their CMPO groups. The SAm/Eu values are less influenced by the platform and range between 0.2 and 2.0, though they can reverse under the influence of the HNO3 concentration (CTV6PICOSAm/Eu = 0.7 at 0.001 M HNO3 to 1.2 at 0.01 M HNO3) or by changing the platform (CTV(0, 3 or 6)MPMA from SAm/Eu = 0.4 to 1.6 for tritMPMA both at 0.001 M HNO3). For the CMPO derivatives the SAm/Eu values are most consistent, ranging from 1.4 to 1.8.