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Title: Synthesis and Characterization of the Actinium Aquo Ion

Abstract

Metal aquo ions occupy central roles in all equilibria that define metal complexation in natural environments. These complexes are used to establish thermodynamic metrics (i.e., stability constants) for predicting metal binding, which are essential for defining critical parameters associated with aqueous speciation, metal chelation, in vivo transport, and so on. As such, establishing the fundamental chemistry of the actinium(III) aquo ion (Ac-aquo ion, Ac(H 2O) x 3+) is critical for current efforts to develop 225Ac [t 1/2 = 10.0(1) d] as a targeted anticancer therapeutic agent. However, given the limited amount of actinium available for study and its high radioactivity, many aspects of actinium chemistry remain poorly defined. We overcame these challenges using the longer-lived 227Ac [t 1/2 = 21.772(3) y] isotope and report the first characterization of this fundamentally important Ac-aquo coordination complex. Our X-ray absorption fine structure study revealed 10.9 ± 0.5 water molecules directly coordinated to the Ac III cation with an Ac–O H2O distance of 2.63(1) Å. This experimentally determined distance was consistent with molecular dynamics density functional theory results that showed (over the course of 8 ps) that Ac III was coordinated by 9 water molecules with Ac–O H2O distances ranging from 2.61 to 2.76more » Å. Lastly, the data is presented in the context of other actinide(III) and lanthanide(III) aquo ions characterized by XAFS and highlights the uniqueness of the large Ac III coordination numbers and long Ac–O H2O bond distances.« less

Authors:
ORCiD logo; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1344367
Report Number(s):
LA-UR-16-28891
Journal ID: ISSN 2374-7943; TRN: US1700898
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Central Science
Additional Journal Information:
Journal Volume: 3; Journal Issue: 3; Journal ID: ISSN 2374-7943
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Ferrier, Maryline G., Stein, Benjamin W., Batista, Enrique R., Berg, John M., Birnbaum, Eva R., Engle, Jonathan W., John, Kevin D., Kozimor, Stosh A., Lezama Pacheco, Juan S., and Redman, Lindsay N. Synthesis and Characterization of the Actinium Aquo Ion. United States: N. p., 2017. Web. doi:10.1021/acscentsci.6b00356.
Ferrier, Maryline G., Stein, Benjamin W., Batista, Enrique R., Berg, John M., Birnbaum, Eva R., Engle, Jonathan W., John, Kevin D., Kozimor, Stosh A., Lezama Pacheco, Juan S., & Redman, Lindsay N. Synthesis and Characterization of the Actinium Aquo Ion. United States. doi:10.1021/acscentsci.6b00356.
Ferrier, Maryline G., Stein, Benjamin W., Batista, Enrique R., Berg, John M., Birnbaum, Eva R., Engle, Jonathan W., John, Kevin D., Kozimor, Stosh A., Lezama Pacheco, Juan S., and Redman, Lindsay N. Wed . "Synthesis and Characterization of the Actinium Aquo Ion". United States. doi:10.1021/acscentsci.6b00356. https://www.osti.gov/servlets/purl/1344367.
@article{osti_1344367,
title = {Synthesis and Characterization of the Actinium Aquo Ion},
author = {Ferrier, Maryline G. and Stein, Benjamin W. and Batista, Enrique R. and Berg, John M. and Birnbaum, Eva R. and Engle, Jonathan W. and John, Kevin D. and Kozimor, Stosh A. and Lezama Pacheco, Juan S. and Redman, Lindsay N.},
abstractNote = {Metal aquo ions occupy central roles in all equilibria that define metal complexation in natural environments. These complexes are used to establish thermodynamic metrics (i.e., stability constants) for predicting metal binding, which are essential for defining critical parameters associated with aqueous speciation, metal chelation, in vivo transport, and so on. As such, establishing the fundamental chemistry of the actinium(III) aquo ion (Ac-aquo ion, Ac(H2O)x3+) is critical for current efforts to develop 225Ac [t1/2 = 10.0(1) d] as a targeted anticancer therapeutic agent. However, given the limited amount of actinium available for study and its high radioactivity, many aspects of actinium chemistry remain poorly defined. We overcame these challenges using the longer-lived 227Ac [t1/2 = 21.772(3) y] isotope and report the first characterization of this fundamentally important Ac-aquo coordination complex. Our X-ray absorption fine structure study revealed 10.9 ± 0.5 water molecules directly coordinated to the AcIII cation with an Ac–OH2O distance of 2.63(1) Å. This experimentally determined distance was consistent with molecular dynamics density functional theory results that showed (over the course of 8 ps) that AcIII was coordinated by 9 water molecules with Ac–OH2O distances ranging from 2.61 to 2.76 Å. Lastly, the data is presented in the context of other actinide(III) and lanthanide(III) aquo ions characterized by XAFS and highlights the uniqueness of the large AcIII coordination numbers and long Ac–OH2O bond distances.},
doi = {10.1021/acscentsci.6b00356},
journal = {ACS Central Science},
issn = {2374-7943},
number = 3,
volume = 3,
place = {United States},
year = {2017},
month = {2}
}

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