This dissertation describes the synthesis and characterization of several types of fullerene polyadducts including: 6,9,12,15,18-pentakisorgano-1-hydro[60]fullerenes, 6,9,12,15-tetrakisorgano[60]fullerenes, and 1,4-bisbenzyl[60]fullerenes as well as the performance of several in photovoltaic devices. Several of these projects are collaborations with material scientists and some are original research projects.

Carbon-based nanostructures are viewed as the next-generation components for advanced nanoelectronics. Offering exceptional properties such as low-current requirements and design-based optimization, these π-conjugated molecular structures show promise in outpacing the use of current transistor technologies. To fabricate and accurately study these molecules, it is necessary to utilize synthetic strategies that produce precise and defect-free structures. Thankfully, on-surface synthesis allows for the fabrication of defect-free conjugated polymers allowing in-situ visualization via scanning probe microscopies. This method typically uses a combination of polymerization and cyclization reactions to afford graphene-based nanostructures on a metal surface. Through on-surface synthesis, a number of organic molecular precursors can be sublimed into gas phase and vapor-deposited onto a metal surface, usually gold(111), which is held at a constant temperature. Due to the catalytic activity and mobility of the selected metal, this annealing process often affords organized networks of organic building blocks. Further heating leads to the cleavage of C-X bonds in the aryl-halogen precursors, giving radicals that recombine to form covalent bonds that are typically uncontrolled in solution or gas-phase reactions. Chapter 1 of this work is meant to outline the background of organic materials in electronic applications and introduce a timeline of graphene nanoribbons synthesized on metal surfaces. Chapter 2 describes the synthesis of tetraphenyl-hex-3-en-1,5-diyne, a molecular model for the Hopf cyclization reaction leading to polycyclic aromatic compounds, here chrysene derivatives. We wanted to study the potential of this π-system as reaction pathway to chrysene and larger polycyclic aromatic compounds on Au(111), and ultimately, graphene nanoribbons. It was found that this molecule undergoes two sequential Hopf cyclizations at temperatures that are much lower than calculated or experimental Hopf cyclization reactions. Chapter 3 expands on this work by discussing the synthesis of a diiodo derivative of tetraphenyl-hex-3-en-1,5-diyne. This molecular precursor is capable of pre-polymerizing on gold(111), providing an entry into the fabrication of graphene nanoribbons. Chapter 4 of this works explores the possibilities of using combinatorial Ullman coupling and Hopf cyclization to generate graphene nanoribbons from annulated tetraphenyl-hex-3-en-1,5-diyne. Overall, this works aims to divulge new and exciting synthetic pathways for developing carbon-based materials for electronic applications. Chapters 2 through 4 were conducted in collaboration with EMPA − Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland, and the University of Bern, Switzerland. Chapter 5 of this work looks at the synthesis of a 1,4-butadiyne molecular precursors for the fabrication of graphene nanoribbons on Au(111) Chapter 6 was motivated by the dramatic switch to remote-learning during the COVID-19 pandemic at UCLA. During this time, student interactions in online discussion sections were monitored to determine the best course characteristics for break-out room engagement. This work hopes to highlight important features that could be useful for in-person or remote courses in the future.

Chapter 1 provides an overview on the synthesis of graphene nanoribbons. Various types of edge structures and bottom-up synthetic strategies, on-surface and in-solution, are covered before discussing our group’s third approach, solid-state. This is followed by a description of the effect of heteroatomic substitutions on electronic properties of GNRs. Lastly a brief discussion on other semiconducting polymer structure and charge transfer properties are introduced.

Chapter 2 details the synthesis of N = 8 armchair graphene nanoribbons (GNRs) using a two-step solid-state method. Four diarylbutadiyne precursors undergo topochemical polymerization to four distinct polydiacetylene (PDA) polymers, which subsequently cyclodehydrogenate and undergo side chain fragmentation to afford the same N =8 armchair GNR. Various spectroscopic and imaging techniques are used to characterize this transformation, in addition to calculations of the cyclization process on a model system used to verify the mechanism.

Chapter 3 describes the synthesis of GNRs with a fjord-edge structure and site-specific nitrogen substitutions using the two-step approach above. Two dipyridylbutadiyne precursors polymerize and cyclize to afford N = 8 fjord-edge N-GNRs, with side chains still intact. Spectroscopic characterization, imaging and mechanistic calculations of a pyridyl model system verify the transformation from butadiyne to GNR.

Lower the barrier of Hopf cyclizations, a step towards GNRs in our solid-state approach, through introduction of strained cycloalkenes could lead to room temperature GNR syntheses. Chapter 4 details the synthesis of two polydiacetylene synthons containing norbornadiene, a bis(norbornadienyl)1,3-butadiyne and trans-bis(norbornadienyl)enediyne. Challenges towards synthesizing both monomer units and future applications of other trans-enediynes towards GNRs are discussed.

Chapter 5 describes the synthesis of an amphiphilic semiconducting polymer, poly(cyclopentadithiophene-alt-thiophene) (PCT), according to a set of design rules aimed at straightening the polymer backbone in order to reduce polymer disorder and increase conductivity. The design rules are 1) hydrophobic polymer backbone and hydrophilic side chains, 2) alternating co-polymer such that all the side chains reside on one side, 3) side chains branched off an sp3 carbon to create a 3D wedge shape, and 4) complementary bond angles between monomer units to achieve a 180� dihedral angle. The solution phase of the polymer is characterized by small angle X-ray scattering (SAXS) and imaged using cryo-transition electron microscopy (TEM).

Applications of PCT towards controlling electron donor-acceptor complexes are explored in Chapter 6. PCT and poly(fluorene-alt-thiophene) (PFT), are complexed with two electron acceptors, a charged perylenediimide and a series of charged bis-pyrrolidium functionalized fullerenes. The structure of these co-assemblies are characterized by small angle X-ray scattering and photoluminescence quenching, concluding that complementary geometries between the polymer micelle and acceptor shapes result in increased amounts of photoluminescence quenching.

Chapter 1 describes the development and spectroscopic investigation of a novel synthetic route to N=8 armchair graphene nanoribbons from polydiacetylene polymers. Four distinct diphenyl polydiacetylene polymers are produced from the crystal-phase topochemical polymerization of their corresponding diphenyl-1,4-butadiynes. These polydiacetylene polymers are transformed into spectroscopically indistinguishable N=8 armchair graphene nanoribbons via simple heating in the bulk, solid-state. The stepwise transformation of polydiacetylenes to graphene nanoribbons is examined in detail by the use of complementary spectroscopic methods, namely solid-state nuclear magnetic resonance, infrared, Raman and X-ray photoelectron spectroscopy. The final morphology and width of the nanoribbons is established through the use of high-resolution transmission electron microscopy. Chapter 2 chronicles the implementation of a similar approach to N=12 armchair graphene nanoribbons from a dinaphthyl substituted polydiacetylene polymer. The mild nature of the process and pristine structure of the nanoribbons is again confirmed with the use of spectroscopic and microscopic methods. The chapter concludes with preliminary electrical measurements of the nanoribbons confirming that they are indeed conductive. Chapter 3 details the development of a synthetic route to diaryl trans-enediynes as structural models of individual reactive units within a polydiacetylene polymer. The trans-enediynes described are found to undergo three distinct annulation reactions depending on reaction conditions. Finally, the synthetic routes developed are utilized to access diethynyl [5]helicenes and phenanthrenes which fueled studies on the mechanism of the Bergman polymerization reaction.