Theses and Dissertations

ORCID

https://orcid.org/0000-0002-4207-4206

Issuing Body

Mississippi State University

Advisor

Creutz, Sidney E.

Committee Member

Hollis, Thedford K.

Committee Member

Webster, Charles E.

Committee Member

Scott, Colleen

Committee Member

Emerson, Joseph P.

Date of Degree

8-8-2023

Document Type

Dissertation - Open Access

Major

Chemistry

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Arts and Sciences

Department

Department of Chemistry

Abstract

Cooperativity between the metal center and the ligand has been shown in nature to be an important feature of systems that catalyze two-electron processes that first-row transition metals usually cannot catalyze on their own. In these cases, the ligand acts as a site of reactivity that in many instances can store electrons or react directly with substrates in solution. The design and study of systems where there is synergy between the metal and the ligand have been leveraged to catalyze polymerization and hydrogenation-type reactions as well as the activation of small molecules such as dihydrogen. Specifically, the pyridine(diimine) ligand scaffold has been reported to store up to three electrons on the ligand backbone that can later be used in catalysis. Wanting to expand on this work, we have designed and synthesized a new pincer that has redox-noninnocent properties similar to pyridine(diimine) ligands but incorporates a pyrazine ring instead of a pyridine ring to give rise to new electronic properties. Pyrazine(diimines) also have an uncoordinated 4-position nitrogen that can be further functionalized to fine-tune the electronic properties of the ligand. In Chapter II we will discuss bisligated iron(II) pyrazine(diimine) (PZDI) complexes in three different oxidation states where we used spectroscopic and computational techniques as well as comparison to known pyridine(diimine) iron(II) complexes to support our assignments of ligand-based reduction. Chapter III will focus on monoligated pyrazine(diimine) iron(II) complexes as compared to analogous pyrazine(diimine) systems where the central metal is manganese, cobalt, or nickel, as well as compare our pyrazine(diimine) iron(II) complexes to reported pyridine(diimine) iron(II) analogs. We have also synthesized a new inverted pyridine(diimine) ligand scaffold that has an NCN binding pocket, which will be discussed in Chapter IV. In the design of the inverted pyridine(diimine) ligand we have left in place the 4-position nitrogen from our previously described pyrazine(diimine) ligand, maintaining a Lewis basic site for functionalization. Overall, we hope to describe the results we observed with both monoligated and bisligated iron(II) pyrazine(diimine) complexes as well as discuss our approach to the design of and progress towards a new inverted pyridine(diimine) ligand scaffold.

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