A Coordination Chemistry Approach to Nano- and Supramolecular Material Design

Coleman, Benjamin

doi:https://doi.org/10.21985/n2-5dw2-pr62

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A Coordination Chemistry Approach to Nano- and Supramolecular Material Design

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The need for complex and sophisticated materials continues to grow as society becomes more advanced. For many chemists, the design of these materials begins by looking towards model molecular systems for the identification of desirable properties and functions. As such, restricting oneself to C, H, N, O, and the other few elements of organic chemistry is inherently limiting to the types of materials that can be achieved. Coordination and organometallic chemistry takes advantage of nearly the entirety of the Periodic Table (e.g. transition metals, lanthanides, actinides, nonmetals) to form compounds with a wide variety of electronic, chemical, and physical properties. As such, coordination chemistry is an ideal platform for the bottom-up construction of next-generation nano- and supramolecular materials. This dissertation uses coordination chemistry to synthesize novel magnetic and stimuli-responsive materials, with a focus on the construction of new infinite coordination polymers. Chapter 1 begins this work with a brief introduction to the core theory behind infinite coordination polymers, transition metal-based metal-organic magnets, and the dynamic Weak-Link Approach (WLA) to supramolecular chemistry. Chapter 2 describes the synthesis and characterization of a series of metal-organic framework magnets. These materials leverage antiferromagnetic coupling between unpaired electrons on transition metal centers and radical ligand-based electrons to engender strong magnetic coupling, leading to higher magnetic ordering temperatures in the subsequent materials. Chapters 3 and 4 of this dissertation explore the WLA for the design of stimuli-responsive coordination polymers and molecular tweezers. The WLA leverages the well-developed coordination chemistry of d8 transition metal ions with hemilabile ligands to construct nanoscale architectures that can be switched between a closed, structurally rigid state and more open, flexible state. In Chapter 3, the design and synthesis of the first series of crystalline, WLA-based coordination polymers is reported. Notably, by studying the response of one of the chains to Cl− anions in solution, we demonstrate that crystalline chain assembly can be controlled via the structural state of imbedded WLA complex subunits. Next, we focus on further developing the chemistry at the core of the WLA and expanding it to include reversible structural switching in an aqueous environment; chapter 4 details initial attempts and challenges in understanding the chemistry of newly synthesized water-soluble WLA complexes. We see adapting the WLA to function within water as the first steps to integrating the WLA with biomacromolecules for the synthesis of novel dynamic, biomaterials. Finally, in chapter 6, future work to further build the WLA towards a platform that can be used to design dynamic inorganic and biomacromolecular materials at increasing length scales and complexity is detailed.

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