Friday, May 26, 2023 - 2:00pm

Abstract: This dissertation describes efforts to expand the area of low oxidation state chemistry for the rare-earth metals and the actinides. The use of the spherically encapsulating 2.2.2-cryptand (crypt) for the isolation of new complexes of +3 and +2 ions of these metals was explored. In addition, X-ray photoelectron spectroscopy (XPS) was used to evaluate the electron configurations of Gd(II) complexes by comparison with Gd(III) analogs. Specifically, Chapter 2 describes the isolation of complexes of Sm(III) and Nd(III) with crypt, [Sm(crypt)(OTf)2][OTf] and [Nd(crypt)(OTf)2][OTf], and their reduction chemistry. The [Ln(crypt)(OTf)2][OTf] complexes reacted with KC8 in THF to form the LnII(crypt)(OTf)2 counterparts. Chapter 3 describes the synthesis and attempted reduction of [Ln(crypt)(OTf)2][OTf] complexes for Ln = La, Ce, and Pr. Unlike their Sm and Nd counterparts, neither chemical nor electrochemical reduction was observed for La and Ce. Chapter 4 describes the extension of the crypt ligand to actinides in collaboration with Dr. Andrew Gaunt and Dr. Conrad Goodwin at Los Alamos National Laboratory (LANL) for An = U, Np, and Pu. Small scale reactions with uranium to make [U(crypt)(OTf)2][OTf] were conducted and used as a method to extend this chemistry to Np and Pu, which are of limited availability. Chapter 5 describes methods using liquid ammonia and sodium metal to attempt reductions of smaller Ln metals encapsulated in the cryptand ligand. This method was explored because Ln-in-crypt complexes of the smaller lanthanides later in the series are not soluble in THF. Chapter 6 describes the exploration of borohydride, (BH4)1-, and thexylborohydride, (H3BCMe2CMe2H)1-, ligands to make THF-soluble LnII-in-crypt complexes. These ligands were used for both Sm and Dy. While evidence suggests that a THF-soluble SmII(crypt)(H3BCMe2CMe2H)2 can be generated, Dy-in-crypt complexes with borohydrides were still not THF-soluble. Chapter 7 describes the isolation of a SmII ion encapsulated in a 2.2.1-cryptand (221crypt) ligand environment, [Sm(221crypt)(OTf)][OTf].  A cryptand with a smaller pocket was explored to see if this could affect the solubility of these cryptand complexes. Instead of making complexes more soluble in THF, the opposite was observed. Chapter 8 describes the isolation of a [TmII(crypt)(OTf)][OTf]2 complex. In comparison to the reductions described in Chapter 2, this complex was not isolated by chemical reduction of a TmIII-in-crypt complex, but rather the reduction of TmIII(OTf)3 with KC8 followed by the addition of crypt. Chapter 9 describes X-ray photoelectron spectroscopy (XPS) measurements made on Gd complexes in different coordination environments, specifically, Gd[(NSiMe3)2]3, Cptet3Gd, [K(crypt)][Gd[(NSiMe3)2]3], and [K(crypt)][Cptet3Gd] and a comparison with cyclopentadienyl analogs.


Sierra Ciccone


Evan's Group


NS1 4112