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Abstract

Molecular self-assembly on surfaces has garnered significant interest as a nanofabrication process due to its ability to organize large assemblies of molecular building blocks with intrinsic properties. Surface-confined two-dimensional (2D) self-assembled monolayers based on small, planar organic and organometallic molecules at the solid-liquid interface have been heavily investigated due to their propensity to produce highly specific patterns that is determined by molecular design, as well as the variation in sample preparation conditions such as solution concentration, temperature, and choice in solvent. The focal point of the research presented in this work is to explore the use of metalloporphyrins, which have been shown to form well-ordered, extensive supramolecular assemblies on atomically flat substrates and can also support axial ligands through covalent interactions through the metal centers, as molecular building blocks to extend the 2D structures into functional 3D systems. In Chapter 2, the preparation, characterization, and self-assembled monolayer formation of Ga(III) meso-tetra(¬n-C10H21)porphyrins [Ga(TC10P)X] with axial oligo-phenylene-ethynylene (OPE) ligands [Ga(TC10P)(OPE)] are discussed. Scanning tunneling microscopy (STM) imaging of the monolayers formed by these complexes at the solid-liquid interface shows that the packing arrangement of these structures is identical to that of the free-base derivative, which shows that the incorporation of tall, pillared structures as axial ligands does not disrupt the formation of self-assembled monolayers in which the porphyrin cores are oriented parallel to the substrate and also indicates that Ga(III)-porphyrin monolayers can be used to anchor functional molecules above the surface. The subsequent chapters focus on Ga-porphyrin complexes prepared through alternative ligand-attachment chemistry. In Chapter 3, the synthesis and characterization of novel Ga-porphyrin-carboxylate and aryloxide complexes are presented. Taking advantage of the facile reactivity of Ga(TC10P)(OH) towards carboxylic acids and aryl alcohols, a variety of novel dyads with functional axial subunits such as chromophores and electroactive centers were prepared. The self-assembly of the newly prepared complexes at the solid-liquid interface is reported in detail in Chapter 4. In Chapter 5, the self-assembly of Ga(TC10P)(OH) at the solid-liquid interface and subsequent attempts to chemically modify the monolayers post-deposition are discussed.

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