The synthesis and stability of endohedral actinium-225(²²⁵Ac@C₆₀)

Author

Jofa Gideon Mwakisege, University of Tennessee, Knoxville

Date of Award

8-2008

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemistry

Major Professor

George Schweitzer

Committee Members

George Kabalka, Jamie Adcock

Abstract

Due to their chemical and thermodynamic stability, fullerenes could play an important role in encapsulation of radionuclides for applications in radio-immunotherapy. In this thesis, we report the first synthesis of actinium endohedral fullerenes. The alpha-emitter Actinium-225 (²²⁵Ac, t_1/2 =10 d) was trapped in fullerenes by the direct current (D.C) arc discharge-catcher method in a He atmosphere. Endohedral ²²⁵Ac and the bulk of fullerene C₆₀ was dissolved from the catcher electrode (a Pt disk covered with a thin layer of C₆₀) in toluene under N₂, and converted to the malonic ester derivative. Repeated washing of the organic phase with dilute HNO₃ demonstrated that a small fraction of ²²⁵Ac (1.0 %) could not be removed from the organic phase and presumably was inside the fullerenes. The Fr- 221 (the α-decay daughter of ²²⁵Ac), however, was observed to be leaking from the cage probably as a result of nuclear recoil. The cage stability was enhanced significantly by coupling the fullerene surface with organic adducts. After repetitive extractions, a 45% fraction of original activity was still retained in the cage. The radioactivity distribution coefficients {Kd = (²²⁵Ac radioactivity in aqueous- phase)/ (²²⁵Ac radioactivity in organic phase)} were investigated. We propose that, if Kd and back to back extractions, collectively are to be study in timely manner, the rate in which ²²⁵Ac@C₆₀ dissociate into individual components would be obtained.

Recommended Citation

Mwakisege, Jofa Gideon, "The synthesis and stability of endohedral actinium-225(²²⁵Ac@C₆₀). " Master's Thesis, University of Tennessee, 2008.
https://trace.tennessee.edu/utk_gradthes/3685