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Title: A Macrocyclic Chelator That Selectively Binds Ln 4+ over Ln 3+ by a Factor of 10 29

A tetravalent cerium macrocyclic complex (CeLK 4) was prepared with an octadentate terephthalamide ligand comprised of hard catecholate donors and characterized in the solution state by spectrophotometric titrations and electrochemistry and in the crystal by X-ray diffraction. The solution-state studies showed that L exhibits a remarkably high affinity toward Ce 4+, with log β 110 = 61(2) and ΔG = -348 kJ/mol, compared with log β 110 = 32.02(2) for the analogous Pr 3+ complex. In addition, L exhibits an unusual preference for forming CeL 4- relative to formation of the analogous actinide complex, ThL 4- , which has β 110 = 53.7(5). The extreme stabilization of tetravalent cerium relative to its trivalent state is also evidenced by the shift of 1.91 V in the redox potential of the Ce 3+/Ce 4+ couple of the complex (measured at -0.454 V vs SHE). The unprecedented behavior prompted an electronic structure analysis using L 3 - and M 5,4-edge X-ray absorption near-edge structure (XANES) spectroscopies and configuration interaction calculations, which showed that 4f-orbital bonding in CeLK 4 has partial covalent character due to ligand-to-metal charge transfer (LMCT) in the ground state. The experimental results are presented in the context of earlier measurementsmore » on tetravalent cerium compounds, indicating that the amount of LMCT for CeLK 4 is similar to that observed for [Et 4N] 2[CeCl 6] and CeO 2 and significantly less than that for the organometallic sandwich compound cerocene, (C 8H 8) 2Ce. A simple model to rationalize changes in 4f orbital bonding for tri- and tetravalent lanthanide and actinide compounds is also provided.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [3] ;  [3] ;  [5] ;  [3] ;  [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); California State Polytechnic Univ., Pomona, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Canadian Light Source (CLS), Saskatoon, SK (Canada)
Publication Date:
Report Number(s):
LA-UR-16-23578
Journal ID: ISSN 0020-1669; ark:/13030/qt921839xr
Grant/Contract Number:
AC02-05CH11231; AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 55; Journal Issue: 20; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Inorganic and Physical Chemistry
OSTI Identifier:
1377540
Alternate Identifier(s):
OSTI ID: 1407873