Bottom-up synthesis is increasingly becoming the method of choice for assembling and studying novel nanomaterials. Whereas more traditional top-down methods may lead to mixtures of products and suffer from reproducibility issues, bottom-up approaches offer atomistic control over the material's structure. Bottom-up synthesis can also produce materials that would otherwise be unobtainable with top-down methodologies. Finite substructures of carbon nanotubes (CNTs) are one such example. The work encompassed in this thesis details the study of two related classes of CNT substructures: the cycloparaphenylenes (CPPs) and [5.7]ncyclacenes. Cycloparaphenylenes are a class of graphitic material with many unique properties that make them intriguing candidates for study in a variety of electronic applications. Chapter 1 describes the current state of CPP research, from preliminary synthesis to fundamental understanding of their properties. To optimize device performance, carbon materials are often doped with heteroatoms. Towards this end, the synthesis of a series of nitrogen-doped [8]CPPs (N-[8]CPPs) are detailed in Chapter 2. Nitrogen is incorporated into the CPP structure by way of the reductive aromatization strategy used for the all carbon CPPs, replacing 1,4-dibromobenzene with 2,5-dibromopyridine. The synthesis utilizes oxidatively masked benzenes to assemble less strained, macrocyclic precursors. Through the divergent nature of the synthesis, macrocycles containing up to three nitrogen atoms at precise locations are prepared. Macrocycles are aromatized via a single electron reduction to reveal the final N-CPP structures. Chapter 3 details the full characterization of the properties of the novel N-[8]CPPs. The differences between the N-[8]CPPs and [8]CPP are rationalized in the context of DFT studies. Finally, the study of 1N-[8]CPP and [8]CPP as novel electrode materials in supercapacitor cells is presented. Preliminary results show that the CPP electrodes are more conductive than the activated carbon control group, but the specific capacitances are found to be low. Finally, Chapter 4 describes the computational study of a novel family of macrocycle: [5.7]ncyclacenes. [5.7]ncyclacenes are isomers of the sought after [n]cyclacenes. Unlike their isomeric cousins, DFT studies show that [5.7]ncyclacenes have stable, closed-shell singlet ground states with relatively low strain energies. NICS values also show the molecules to be non-aromatic. These results suggest that with proper synthetic design, the [5.7]ncyclacenes should be accessible synthetically.

Commonly viewed as the shortest cross sections of armchair carbon nanotubes (CNTs), cycloparaphenylenes (CPPs) represent a unique class of conjugated macrocycles with rigid backbones. In addition to their utility in seeding the growth of uniform CNTs, these strained nanohoops and their derivatives have unique optoelectronic and supramolecular properties for potential applications in materials science. Herein we present our efforts in designing novel nanohoop architectures and new types of strained macrocycles that serve as building blocks for functional materials. Chapter I briefly reviewed the under-represented reactivity studies of strained aromatic macrocycles. Chapter II describes our early efforts in probing the structure-property relationships of oligophenylene macrocycles focusing on the understanding of the influence of structural bending and cyclic conjugation on the optoelectronic properties. Chapter III reports the reactivity study of 1,4-anthracene-incorporated [12]CPP, a model substrate to examine the feasibility of using anthracene as the functional handle to crosslink nanohoops. Chapter IV presents the synthesis of a molecular propeller with three nanohoop blades and examines its unique hexagonal layered packing structure. In Chapter V, we disclose the synthesis of strained stilbene macrocycles suitable for ring-opening metathesis polymerization (ROMP) as well as the initial ROMP studies of this monomeric system. This dissertation contains previously published and unpublished coauthored materials.

Conjugated macrocycles have emerged as novel structural motifs that modulate the electronic properties of organic molecules because of their strained and contorted structures. Cycloparaphenylenes, known as nanohoops, are a particularly attractive scaffold for the design of new types of carbon nanomaterials because of their size-selective synthesis, radially oriented π-systems and tunable electronic properties. The development of modular syntheses of nanohoops over the past decade should enable the preparation of substituted derivatives that can be tuned for applications in biology and materials science. Chapter I provides a brief overview of conjugated macrocycles recently reported in the literature with a discussion of the structural effects that are responsible for the remarkable properties of this class of molecules. Chapter II highlights a scalable and mild synthetic approach developed in our lab to prepare nanohoop conjugated macrocycles and expands the generality of this methodology with the formal synthesis of natural product Acerogenin E. Chapter III describes the synthesis of cycloparaphenylenes with versatile functional handles and uncovers the reactivity of the strain nanohoop backbone under reaction conditions that promote the formation of radical cations. Chapter IV takes advantage of the functional groups described in chapter III to develop the first example of nanohoops as a new class of biocompatible fluorophores. Chapter V details a novel synthetic approach that enables the incorporation of the linear acene pentacene into the nanohoop backbone and reports our findings on the impact that the macrocyclic structure has on the properties of this organic semiconductor. In summary, the findings discussed in this dissertation provide synthetic strategies for the selective functionalization of nanohoops and highlight this class of molecules as a novel scaffold for the design of new types of carbon nanomaterials. This dissertation includes previously published and unpublished co-authored material.