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Conformational Control of Organic Conjugated Molecules and Macromolecules through Dynamic Noncovalent Bonds
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Torsional conformation of the backbone of a π‐conjugated molecule or macromolecule shapes its solubility, optical and electronic characteristics, rheological behaviors, solid‐state properties, and ultimately materials performances. This dissertation focuses on the on-demand control over the conformation of π-conjugated molecules and macromolecules using dynamic intramolecular noncovalent bonds, such as hydrogen bonds and B←N coordinate bonds. Those dynamic bonds bridged building units in a π-conjugated system so that desired conformations can be induced and then perturbed in a controlled manner. Through such an active manipulation over molecular conformation, optical band gaps, electrochemical properties, solubilities, and processabilities of organic conjugated materials can be tuned on demand. This dissertation begins with a brief introduction of the development of organic conjugated molecules and macromolecules involving a variety of bridging noncovalent bonds (Chapter I). Challenges in this specific field are identified and discussed for future breakthroughs in exploiting the promising potential of these dynamic-noncovalent‐bond‐ bridged π‐conjugated organic materials. Chapter II describes an example of conformational control in a conjugated molecule using intramolecular hydrogen bonds to achieve tailored molecular, supramolecular, and solid-state properties. The fully coplanar conformation of such molecules led to short π–π stacking distances, strong yet controllable aggregation in solution phase, and solid-state self-assembly into one-dimensional nano-/microfibers. Shown in Chapter III, this molecular design is expanded into a macromolecular π-conjugated system. A molecular engineering strategy of chemically inhibiting and regenerating intramolecular hydrogen bonds was developed to resolve the synthetic challenges and processing issues by controlling the backbone conformation. Chapter IV and V discuss the incorporation of intramolecular B←N coordinate bonds into organic conjugated molecules. In Chapter IV, it is demonstrated that the dynamic nature of such coordination allowed for active manipulation of the optical properties by using competing Lewis basic solvents. Described in Chapter V, two rigid molecular constitutions were designed to accommodate redox-active units and B←N coordination into a compact structure. These molecules demonstrated multiple electron transfer processes and multicolor electrochromism. Comprehensive experimental and computational investigations revealed the underlying mechanism of the redox processes, and the critical role of B←N coordination in rendering such redox properties. This dissertation is to understand the fundamental correlation between molecular conformation and materials properties of π-conjugated systems by employing dynamic noncovalent bonds. This dissertation discusses synthetic methodologies to incorporate dynamic noncovalent bonds into organic conjugated molecules and macromolecules. The molecular design principles and structure-property relationships between molecular conformation and materials properties were established. The active manipulation of intramolecular noncovalent bonds led to tunable molecular and supramolecular properties and enabled solution processing of rigid coplanar macromolecules.
Zhu, Congzhi (2019). Conformational Control of Organic Conjugated Molecules and Macromolecules through Dynamic Noncovalent Bonds. Doctoral dissertation, Texas A & M University. Available electronically from