PhD Oral Exam - Jean Louis Do, Chemistry

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Supramolecular materials have shown significant potential for their use in targeted applications such as enzyme mimics in homogeneous catalysis, binding of biological molecules for biomedical applications, and most recently as precursors and building blocks to advanced framework materials. The success and continued development of these materials is supported by well-defined chemical concepts, i.e. intermolecular forces including metal-ligand interactions, hydrogen bonding, halogen bonding, etc., as well as rapid advancements in synthetic, supramolecular, and computational chemistry.

In tandem, there is an essential need for developing such new materials at low cost, using non-toxic and abundant precursors, and in an environmentally friendly fashion. Described herein is the design, study, and self-assembly of new supramolecular metallostructures and cocrystals based on the use of salicylic acid and imidazole as versatile and readily modified coordination motifs. It is the aim of this thesis to understand the fundamentals of how the proposed ligands self-assemble with metal cations of interest under both solution and solvent-free conditions.

The initial chapters of this thesis explore the use of commercially available and industrially relevant salicylic acid units, bridged using either aromatic terephthalic acid-based or aliphatic methylene-based struts. These ditopic ligands are subsequently used to develop families of discrete anionic metallostructures, which include homoleptic double and triple helicates, heteroleptic dinuclear complexes, and homoleptic tetrahedral cages. In addition to demonstrating the selective self-assembly of these structures from di- and trivalent metal cations (Cu2+ and Fe3+, respectively) across a wide range of reaction conditions and synthetic methods, this thesis highlights the opportunity for selected systems to undergo noncovalent or covalent post-synthetic modifications.

The latter chapter of this thesis then explores the use of unfunctionalized imidazole in designed accelerated aging experiments with a divalent metal (Ni2+ in the form of NiO) to obtain a coordination complex cocrystal that had not previously been isolated. The use of an oxide starting material and accelerated aging to complement more traditional metal precursors and solution-based syntheses highlights new opportunities in the design and synthesis of cocrystals. Furthermore, the ability to controllably decompose the obtained cocrystal is demonstrated.

The fundamental studies conducted and detailed herein serve as an advancement in the field of supramolecular chemistry, notably demonstrating the viability of utilizing salicylic acids and imidazole as coordination motifs in the design and discovery of new materials.