Kinetic Selectivity in Reactions of Rare Earth Coordination Compounds Emergent From Differential Excited State Quenching by 4F-States Kevin Parker Ruoff

Format:

Book

Thesis/Dissertation

Author/Creator:

Ruoff, Kevin Parker, author.

Contributor:

University of Pennsylvania. Chemistry., degree granting institution.

Language:

English

Subjects (All):

0485.

0488.

0494.

Local Subjects:

0485.

0488.

0494.

Physical Description:

1 electronic resource (261 pages)

Contained In:

Dissertations Abstracts International 87-07B

Place of Publication:

Ann Arbor : ProQuest Dissertations and Theses, 2025

Language Note:

English

Summary:

Rare earth elements (REs; yttrium, scandium, and the lanthanides) have electronic structures that engender them with optical and magnetic properties useful in advanced technologies. Increasing demand for REs raises concerns about their unstable supply chains, which are hindered by challenging separations chemistry. Industry standard processes exploit small differences in ionic radii to affect separations, rendering similarly sized element separations inefficient. It is of great interest to develop new separations methods that rely on a property other than size, such as electronic structure. The progressive filling of the 4f-subshell across the lanthanide series manifests metal-specific excited states and energy transfer to these states can disrupt photochemical reactions and lead to reaction-dampening based on competitive energy transfer rates. In this dissertation, three photochemical reactions are discussed that exemplify this concept. Chapter 1 presents a perspective on the idea of rare earth separations by excited state quenching (SES-Q). In Chapter 2, a novel light-induced oxygen-atom transfer reaction is described to proceed at different rates for the similarly-sized REs dysprosium and yttrium. The diversion of reactive NMMO* excited state energy by Dy3+-based f-states is shown to be the cause of the reaction rate attenuation for that cation by transient absorption spectroscopy. In Chapter 3, a series of kinetically inert RE coordination compounds appended with a photoreactive anthracene arm is described and the kinetics of photodimerization of the complexes are studied. Two mechanisms are postulated to be in competition: a singlet pathway and a triplet pathway that can be eliminated by the addition of a triplet quencher. The rate of the singlet-exclusive pathway correlates well with singlet excited state lifetimes, providing a methodology for screening potential reaction candidates using excited state dynamics studies. In Chapter 4, the photoisomerization rate of a merocyanine photoswitch bound to early lanthanides is found to proceed at element-dependent rates using in situ illumination UV-Vis spectroscopy. Neodymium attenuates the reaction significantly relative to praseodymium, which is notable because of the similar sizes of these cations. These three reactions are discussed with regard to their candidacy for kinetically selective reactive separations of REs

Notes:

Advisors: Schelter, Eric J. Committee members: Walsh, Patrick J.; Berry, Donald H.; Subotnik, Joseph E.

Source: Dissertations Abstracts International, Volume: 87-07, Section: B.

Ph.D. University of Pennsylvania 2025

Vendor supplied data

Local Notes:

School code: 0175

ISBN:

9798276005744

Access Restriction:

Restricted for use by site license