The highly interdisciplinary study of molecular magnetism spans a wide array of topics, ranging from spintronics and quantum computing to
enzyme function and MRI contrast agents. At the core of all these fields is the study of materials whose properties can be controlled through
the rational design of molecules. The chemical tailoring of molecular magnetic properties can only be achieved by understanding the relationship
between the physical and electronic structures. In this dissertation, the interplay between structure and physical properties is probed using a
variety of magnetic resonance techniques. In Chapter 1, we give a succinct overview of the various methods utilized in this dissertation. We
first describe the experimental methods including electron paramagnetic resonance (EPR), 57Fe nuclear gamma resonance (Mössbauer) spectroscopy,
electron double resonance detected nuclear magnetic resonance (ELDOR-NMR), and Fourier transform far-infrared (FTIR) spectroscopy. In addition
to the introduction of each technique, we describe how the data is analyzed and what quantities may be extracted from each method. We also
introduce the quantum chemical methods used to rationalize the spectroscopic parameters. In Chapter 2, we investigate a recently reported Fe-V
triply bonded species, [V(iPrNPPh2)3FeI], using high frequency EPR (HFEPR), field- and temperature-dependent 57Fe Mössbauer spectroscopy, and
high-field ELDOR-NMR. From the use of this suite of physical methods, we probe the electron spin distribution as well as the effects of
spin-orbit coupling on the electronic structure. This is accomplished by measuring the effective g – factors as well as the Fe/V electro –
nuclear hyperfine interaction tensors of the spin S = ½ ground state. We have rationalized these tensors in the context of ligand field theory
supported by quantum chemical calculations. This combined theoretical and experimental analysis suggests that the S = ½ ground state originates
from a single unpaired electron predominately localized on the Fe site. Chapter 3 describes a combined HFEPR and variable-field Mössbauer
spectroscopic investigation of a pair of bimetallic compounds with Fe-Fe bonds, [Fe(iPrNPPh2)3FeR] (R = ≡NtBu and PMe3). Both of these compounds
have high spin ground states, where R= PMe3 (S = 7/2) and the R= ≡NtBu displays (S = 5/2). The ligand set employed in this work encapsulates
each Fe site in a different coordination environment. This results in polarized bonding orbitals which engender each nuclear site with unique
hyperfine tensors as revealed by Mössbauer spectroscopy. Absent the metal-metal bond, the tris-amide bound site in both compounds is expected to
be Fe(II). To gain insight into the local site electronic structure, we have concurrently studied a compound containing a single Fe(II) in a
tris-amide site. Our spectroscopic studies have allowed us to assess the electronic structure via the determination of the zero field splitting
parameters and 57Fe electronuclear-hyperfine tensors for the entire series. Through the insight gained in this study, we propose some strategies
for the design of polymetallic single molecule magnets where the metal-metal interactions are mediated by the formation of covalent bonds
between metal centers. Recently, a great deal of the work in molecular magnetism has moved away from polymetallic compounds and towards
molecules containing only a single magnetic ion. A critical challenge in this endeavor is to ensure the preservation of orbital angular momentum
in the groundstate. The stabilization of the ground state orbital moment generates the strong magnetic anisotropy which is often required for
the design of magnetic materials. The presence of unquenched orbital angular momentum can be identified by significant shifts in the g-value
away from the free ion value. In an initial report of a Ni(I) coordination complex, which was found to exhibit field-induced slow magnetic
relaxation, no EPR signal was observed. Given the expectation that orbital angular momentum can shift the g-values beyond the range expected for
a typical S= ½ system, we have reexamined this compound using multi-frequency EPR and field-dependent FTIR spectroscopy. Through a combined
spectroscopic and theoretical effort, we have characterized the effect of first order spin-orbit coupling on the electronic structure. The final
report, Chapter 5, examines an exciting new class of photomagnetic materials based on bisdithiazolyl radicals. These materials, and others with
magnetic properties that can be modulated via optical excitation, offer enticing opportunities for the development of next generation
technologies. The dimorphic system in this study crystallizes in two phases, one composed of diamagnetic dimers and the other of paramagnetic
radicals. Here we report on the use of high-field electron paramagnetic resonance spectroscopy to characterize both the thermally- and
light-induced transitions in the dimer phase. During the course of this study we show that signals originating from residual radical defects in
the dimer phase can be differentiated from those arising from the radical phase. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the
requirements for the degree of Doctor of Philosophy. / Fall Semester 2018. / October 15, 2018. / Includes bibliographical references. / Stephen Hill, Professor Co-Directing Dissertation; Michael Shatruk, Professor Co-Directing Dissertation;
Peng Xiong, University Representative; A. Eugene DePrince, III, Committee Member; Oliver Steinbock, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_661193 |
| Contributors | Greer, Samuel Michael (author), Hill, S. (professor co-directing dissertation), Shatruk, Mykhailo (professor co-directing dissertation), Xiong, Peng (university representative), Steinbock, Oliver (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Chemistry and Biochemistry (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (144 pages), computer, application/pdf |
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