Thesis advisor: Shih-Yuan Liu / Described herein are four projects focused on the elaboration of aromatic 1,2-azaborine core structures through late-stage functionalization strategies. In the first chapter, the gram scale, protecting group-free synthesis of the direct BN isostere of benzene is developed. This protocol is used to produce large quantities of pure 1,2-azaborine suitable for use in fundamental investigations. Second, the first general solution for the functionalization of the C4, C5, and C6 ring positions of 1,2-azaborines is described, featuring iridium catalyzed C-H borylation as the key strategy. Azaborine boronates produced via this method are successfully elaborated through cross coupling and oxidation to access azaborines that serve as N,N-ligands for electrophilic boron sources. The third project is an extension of the borylation/cross coupling project, and introduces the first polymer consisting of repeating azaborine units that displays highly efficient extension of conjugation along the azaborine chain. Finally, a copper catalyzed radical process is developed that enables removal of azaborine boron protecting groups during synthetic routes to simple azaborine targets of high interest. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

This dissertation explores the use of photoelectron imaging spectrometry to probe the molecular electronic structure of various chemical systems, with an emphasis on photoelectron angular distributions. Experimental ion generation, mass selection, laser photodetachment, and photoelectron ion imaging were all done in a photoelectron imaging spectrometer described in detail. Results from simplistic systems, OH- and CH-, are used to illustrate the general and fundamental capabilities of imaging spectroscopy and angular distributions. This illustration is then expanded when both qualitative and quantitative analyses of photoelectron angular distributions are used to aid in the understanding of the electronic structure of several heterocyclic aromatic systems. First a qualitative analysis aids in the exploration of the electronic structure of thiophenide, C₄H₃S⁻, and furanide, C₄H₃O⁻. Ground and excited C₄H₃S and C₄H₃O radical states are observed, and bond dissociation energies are defined. Next, a new model used to qualitatively analyze photoelectron angular distributions resulting from mixed s - p hybrid states is presented and applied to detachment from pyridinide, C₅H₄N⁻; as a benchmark system. Before further exploring this model, the synthesis of several deuterated heterocyclic compounds is presented in order to determine the experimentally produced systems in our experimental setup. The electronic structure of the resultant molecules oxazolide, C₃H₂NO⁻, and thiazolide, C₃H₂NS⁻; are then investigated. Using this new qualitative model, the mixed s - p states model, to evaluate the angular distributions of the systems, the hybridization of the anion molecular orbitals is probed. Comparison of the photoelectron angular distributions that are modeled for each heterocyclic aromatic system yields several trends relating aromatic stabilization, molecular hybridization, and bond dissociation energies. A new qualitative model is then presented to evaluate photoelectron angular distributions resulting from mixed p - d states and applied to detachment from NO⁻. Finally, new ideas and directions are proposed.

A series of photochromic bisthienylethenes (BTE) chromophores with different central ethene bridges were synthesized. Up to date, the rational design of BTE have been mainly carried out on the side aryl groups. In our work, the influence of the aromaticity of the central ethene bridge on the photochromic properties was studied. Moreover, unlike in the literature where most of BTE have a five-membered ring bridge, six-membered ring bridges were used. In Chapter 1, examples of photochromes are given, along with the main definitions. Chapter 2 deals with BTTE, a BTE with a benzobisthiadiazole bridge and with excellent photochromic properties. c-BTTE, the closed isomer, exhibits excellent thermal stability in various solvents and in the solid state. Its fluorescence can be modulated by solvato- and photochromism. It eliminates the usual bias of thermal back reaction, typical of BTE with a six-membered ring ethene bridge. Chapter 3 is devoted to compounds with bridges having different aromaticities (BTE-NA, BTA and BTTA). Their fluorescence can be modulated by solvato- and photochromism. The relation between aromaticity and thermal stability was established: the low aromaticity of the central ethene bridge with benzobisthiadiazole unit leads to a thermal irreversibility for BTTA, and the small energy barrier between the parallel and anti-parallel conformers and the great difference in absorption between BTTA and c-BTTA allow the full conversion from BTTA to c-BTTA. Molecules with a benzothiadiazole bridge, designed for complexation and for switchable nonlinear optical properties were prepared (Chapters 4 and 5). However, the targeted properties were not evidenced up to now.

The synthesis, structure, and reactivity of titanium bis(diimine) complexes supported by 1,2-alternate dimethylsilyl-bridged p-tert-butylcalix[4]arene dianion and 2,2' methylene-bridged 4-methyl, 6-tertbutyl phenol ligands is reported. The molecular structure of [(DMSC)Ti(bpy)2] (28) and [(MBMP)Ti(bpy)2] (55) was characterized by X-ray crystallography. Complexes [(DMSC)Ti(bpy)2] (28), [(DMSC)Ti(dmbpy)2] (29), and [(DMSC)Ti(phen)2] (30) undergoes light-assisted reactions with two or more equivalents of (C6H5)2CO or (p-MeC6H4)2CO to give the corresponding 1-aza-5-oxa-titanacyclopentene complexes 37-42. Similar reactivity was observed with [(MBMP)Ti(bpy)2] (55), [(MBMP)Ti(dmbpy)2] (56), and [(MBMP)Ti(phen)2] (57). The molecular structure of [(MBMP)Ti{kappa-3-OC(C6H5)2C10H7N2}{OCH(C6H5)2}] (58) was characterized by 1H and 13C NMR as well as X-Ray crystallography.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2000. / Includes bibliographical references.

xv, 219 p. : ill. (some col.) / Chemists have long recognized the potential of the BN bond to mimic CC double bonds in aromatic systems. Phenyl and indole are two of the most important arenes in natural systems, as well as medicine, applied chemistry, and materials science. Despite the potential of BN arenes as phenyl and indole mimics in biomolecules, few isoelectronic and isostructural BN biomolecules have been synthesized. Substitution of BN for C=C imparts tunability to aromatic systems, giving new and potentially valuable properties to the resulting molecules. Our group has sought to expand the utility of BN arenes by developing the synthetic arsenal available to chemists seeking to incorporate the BN bond into biological and other organic molecules of importance. The scope of this dissertation is twofold: (1) development of the first "fused" BN indole, including a survey of its reactivity towards electrophiles, synthesis of the parent N -H compound with complete characterization, and a comparison to natural indole and (2) expansion of the synthetic methodologies for constructing 1,2-dihydro-1,2-azaborine derivatives, including complete structural characterization of a family of "pre-aromatic" and aromatic compounds and a protection-free synthesis of azaborines. The contributions outlined in this dissertation expand both the fundamental understanding of BN isosterism in aromatic molecules and the synthetic toolbox for chemists seeking to incorporate BN arenes into biological and other organic motifs. This dissertation includes previously published and unpublished coauthored material. / Committee in charge: Professor Kenneth M. Doxsee, Chair; Professor Shih-Yuan Liu, Advisor; Professor Victoria J. DeRose, Member; Professor Michael M. Haley, Member; Professor Janis Weeks, Outside Member

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京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21594号 / 理博第4501号 / 新制||理||1646(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 依光 英樹, 教授 丸岡 啓二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Thesis advisor: Shih-Yuan Liu / Despite extensive research in B–N-containing aromatic systems (most notably 1,2-azaborines) for their potential use in biomedicine and materials science, development of their oxygen counterparts, 1,2-oxaborines, remains underdeveloped. Presented herein is a straightforward route to access 1,2-oxaborines via a ring-closing metathesis strategy. Attempts to utilize the 1,2-oxaborine as a 1,3-diene in the Diels–Alder cycloaddition for potential application as a 4C + 1O synthon are also presented. Lastly, investigations regarding the aromaticity of the B–O heterocycles is probed using computations and isothermal reaction calorimetry. / Thesis (MS) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Models of chemical bonding are essential for contemporary chemistry. Even the explosive development of the computational resources including, both hardware and software, cannot eliminate necessity of compact, intuitive, and efficient methods of representing chemically relevant information. The Lewis model of chemical bonding, which was proposed eleven years before the formulation of quantum theory and preserves its pivotal role in chemical education and research for more than ninety years, is a vivid example of such a tool. As chemistry shifts to the nanoscale, it is becoming obvious that a certain shift of the paradigms of chemical bonding is inescapable. For example, none of the currently available models of chemical bonding can correctly predict structures and properties of sub-nano and nanoclusters. Clusters of main-group elements and transition metals are of major interest for nanotechnology with potential applications including catalysis, hydrogen storage, molecular conductors, drug development, nanodevices, etc. Thus, the goals of this dissertation were three-fold. Firstly, the dissertation introduces a novel approach to the description of chemical bonding and the algorithm of the software performing analysis of chemical bonding, which is called Adaptive Natural Density Partitioning. Secondly, the dissertation presents a series of studies of main-group element and transition-metal clusters in molecular beams, including obtaining their photoelectron spectra, establishing their structures, analyzing chemical bonding, and developing generalized model of chemical bonding. Thirdly, the dissertation clarifies and develops certain methodological aspects of the quantum chemical computations dealing with clusters. This includes appraisal of the performance of several computational methods based on the Density Functional Theory and the development of global optimization software based on the Particle Swarm Optimization algorithm.