Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2003. / Vita. / Includes bibliographical references. / Iminoacetonitriles have been shown to function as aza dienophiles in intramolecular Diels-Alder reactions, affording substituted quinolizidines and indolizidines. The cycloadducts are formed with a high preference for an exo-orientated cyano group due to the a-amino nitrile anomeric effect. The substrates for these [4+2] cycloadditions are prepared from readily available alcohols via a Mitsunobu reaction with the previously unknown N-cyanomethyltriflamide (HN(Tf)CH₂CN) followed by cesium carbonate promoted elimination of trifluoromethanesulfinate. The a-amino nitrile cycloadducts are versatile synthetic intermediates and can be elaborated via alkylation, reduction, and nucleophilic addition chemistry to provide a variety of substituted and functionalized nitrogen heterocycles. Initial investigations have been undertaken to explore the use of this methodology in the total synthesis of alkaloid natural products. / by David Thomas Amos. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2015. / Vita. Cataloged from PDF version of thesis. / Includes bibliographical references. / Fullerenes and other nanocarbon materials such as carbon nanotubes possess interesting chemical and physical properties. In this thesis, we explore various functionalization methods for nanocarbon materials and their potential applications in photovoltaics and fuel cells. Chapter 1 gives an introduction to the chemistry and applications of fullerenes. In Chapter 2, the syntheses of cyclobutadiene-functionalized fullerenes are described, and the influence of intramolecular a-interaction on the electronic energy of a molecule is explored. The fullerene derivatives are used as electron acceptors in bulk heterojunction organic photovoltaics with polymer donors. In Chapter 3, a series of isobenzofulvene-functionalized fullerenes and their photovoltaic performances are presented. We demonstrate that these n-type materials can generate high opencircuit voltages in organic solar cells and produce higher power conversion efficiencies compared to those of standard devices. In Chapter 4, we utilize fullerene derivatives for electron transport layers in perovskite solar cells. We explore the morphology and stability of fullerene films and demonstrate the fabrication of high performance photovoltaics under low-temperature ambient conditions. In Chapter 5, we study the improvement of organic solar cell performances by the addition of aryne-functionalized fullerenes to active layers as a minority component. In Chapter 6, we describe isoxazoline-functionalized fullerenes and carbon nanotubes and explore their transition metal complexes. Co(II) and Fe(II) complexes on carbon nanotubes are used for electrocatalytic oxygen reduction. / by Ggoch Ddeul Han. / Ph. D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 195-206). / On the terahertz (THz) polaritonics platform, ultrafast optical laser pulses are used to generate and detect THz phonon-polariton wavepackets with full spatiotemporal resolution while they are confined to a thin slab of lithium niobate (LN) or lithium tantalate (LT) that is roughly 30-100 pm thick. Polaritonics is an attractive platform for wave-based computing because of its wealth of capabilities, but still requires the study and development of some critical features before applications can be fully realized. In my thesis work, I investigated and developed two of these features: photonic structures and strong light-matter coupling. In the first phase, we developed a fabrication procedure to pattern high-aspect ratio, optical-quality air holes into slabs of LN and LT, which has been historically difficult to achieve. We then studied the nature of THz wave propagation in the slabs when the size of these air holes was either much smaller or comparable to the THz wavelength. In the long-wavelength limit, where the structures are normally approximated as homogenous media, our findings were used to determine a cutoff-wavelength for operation and design of gradient refractive index devices. In the short wavelength limit, where the structures are termed photonic crystals, our work challenged the universally used definition of the Brillouin zone and presented an alternative definition that was valuable in understanding wave propagation in periodically ordered systems. In the second phase, we demonstrated a novel form of light-matter interaction in the strong coupling regime, where phonons and magnons where strongly coupled to the electric and magnetic fields of THz light, respectively. Our experiments, performed in both waveguide and cavity geometries, conclusively proved the formation of new quasiparticles we termed magnon-phonon-polaritons. We believe our results open up the possibility of using polaritonics for facile and coherent ultrafast control and conversion between photonic, phononic, and spin degrees of freedom, and thereby provides a promising avenue through which to explore THz wave-based computing. Our cavity geometry and sensitive detection scheme should also provide a means by which to pursue the field of THz cavity quantum electrodynamics. / by Prasahnt Sivarajah. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Vita. / Includes bibliographical references (p. 259-271). / In this thesis, I demonstrate that measurements of electronic-structure-induced splittings in the rotational spectrum of a vibrationally excited state can identify the nature and extent of the distortion of the equilibrium electronic wavefunction and thereby provide a measure of progress along a reaction coordinate. One-dimensional models of the large amplitude bending reaction coordinates and their associated electronic signatures are constructed for two prototypical unimolecular isomerizations: acetylene<-->vinylidene (HCCH<-->CCH2), and hydrogen cyanide$hydrogen isocyanide (HCN<-->HNC). The nuclear quadrupole hyperne structures of HCN and HNC are distinct at their equilibrium geometries due to the dissimilar natures of bonding in the vicinity of the 14N nucleus. High resolution rotational spectroscopy has been used to determine the hyperne coupling parameters for the ground and excited vibrational levels of HCN and HNC, with up to ten quanta of bending excitation in HCN and up to four quanta in HNC. These spectra reveal the evolution of electronic structure along the isomerization path. Large amplitude local-bending vibrational eigenstates of the ... state of acetylene are shown to be unique in that they possess significant electric dipole moments as a result of the dynamical symmetry breaking in the local-mode limit. Stimulated emission pumping (SEP), through Franck{Condonforbidden vibrational levels of the A~ 1Au state, has been employed to populate the lowest few eigenstates that manifest large amplitude local-bending behavior. / (cont.) Locating appropriate SEP intermediate states has required thorough analysis of the A~-state level structure, particularly the overtones and combination levels involving the nearly degenerate low frequency bending modes, 04 and 06, that are directly related to two possible paths for trans{cis isomerization on the excited state surface. Recent developments in chirped-pulse rotational spectroscopy will enable identification of the higher energy local-bending eigenstates, which approach the acetylene<-->vinylidene transition state, based on their predicted Stark coefficients. / by Adam H. Steeves. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2010 / Vita. Cataloged from PDF version of thesis. / Includes bibliographical references. / I. Total Synthesis of All Class III Galbulimima Alkaloids We describe the total synthesis of (+)- and (-)-galbulimima alkaloid 13, (-)-himgaline anad (-)-himbadine. The absolute stereochemistry of natural (-)-galbulimima alkaloid 13 is revised to 2S. Sequential use of catalytic cross-coupling and cross-metathesis reactions followed by an intramolecular Diels-Alder reaction provided the required trans-decalin AB-ring system and masked the Cl 6-carbonyl as an N-vinyl carbamate for late stage unveiling in the form of the necessary C16-enone. A vinyl-radical cyclization secured the C-ring while successful execution of our strategy for introduction of the CDE-ring system in complex galbulimima alkaloids provided the target pentacycle with complete diastereoselection. II. Total Synthesis of (-)-Himandrine We describe the first total synthesis of (-)-himandrine, a member of the class II galbulimima alkaloids. Noteworthy features of this chemistry include a diastereoselective Diels- Alder reaction in the rapid synthesis of the tricycle ABC-ring system in enantiomerically enriched form, the use of a formal [3+3] annulation strategy to secure the CDE-ring system with complete diastereoselection, and successful implementation of our biogenetically inspired oxidative spirocyclization of an advanced intermediate. The successful and direct late-stage formation of the F-ring in the hexacyclic core of himandrine drew on the power of biogenetic considerations and fully utilized the inherent chemistry of a plausible biosynthetic intermediate. / by Meiliana Tjandra. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1988. / Vita. / Includes bibliographical references. / by Nathan John Bryson. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006. / Vita. / Includes bibliographical references. / Chapter 1. The first detailed study of the palladium-catalyzed amination of aryl nonaflates is reported. Use of bulky electron-rich monophosphinobiaryl ligands or BINAP allow for the catalytic amination of electron-rich and -neutral aryl nonaflates with both primary and secondary amines. Using XantPhos, the catalytic amination of a variety of functionalized aryl nonaflates resulted in excellent yields of anilines; even 2-carboxymethyl aryl nonaflate is effectively coupled with a primary alkyl amine. Moderate yields were obtained when coupling halo-aryl nonaflates with a variety of amines, where in most cases the aryl nonaflate reacted in preference to the aryl halide. Overall, aryl nonaflates are an effective alternative to aryl triflates in palladium-catalyzed C-N bond-forming processes due to their increased stability under the reaction conditions. Chapter 2. A catalyst comprised of a Pd precatalyst and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl is explored in C-N bond-forming processes. This catalyst displayed unprecedented stability and scope allowing, for the first time, the coupling of substrates bearing a carboxylic acid or a primary amide. / (cont.) Also, the more bulky catalyst system Pd/2-tert-butylphosphino-2',4',6'-triisopropylbiphenyl was found to be effective for the Narylation of 2-aminoheterocycles and weakly basic HN-heterocycles: pyrazole and indazole. The chemoselectivity for amination using these catalysts was explored where the rough order of reactivity for amines is: aryl amines >> primary and secondary alkyl amines > 2-aminoheterocycles > primary amides - HN-heterocycles. Chapter 3. The palladium-catalyzed Suzuki-Miyaura coupling of haloaminoheterocycles and functionalized organoboronic acids using a highly active and stable monophosphinobiaryl ligand, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, efficiently produced aminoheterocyclic biaryl derivatives. This same catalyst was effective in coupling 2-haloaminoaryl compounds with 2-formyl or 2-acetylphenyl boronic acids, providing the fused heterocyclic compounds phenanthridine, benzo[c][1 ,8]naphthridine and benzo[c][1,5]naphthridine in excellent yields. Chapter 4. A water-soluble monophosphinobiaryl ligand, sodium -dicyclohexylphosphino-2',6'-dimethoxybiphenyl-3'-sulfonate, was synthesized by electrophilic sulfonation of the lower-aromatic ring of 2-dicyclohexylphosphino-2',6'- dimethoxybiphenyl. / (cont.) This ligand was utilized in the palladium-catalyzed Suzuki-Miyaura reaction of water-soluble aryl/heteroaryl halides and organoboronic acids. The catalyst displays unprecedented reactivity and stability for Suzuki-Miyaura reactions conducted in water. Chapter 5. A water-soluble monophosphinobiaryl ligand, sodium 2'-(dicyclohexyl-osphanyl)-2,6-diisopropyl-biphenyl-4-sulfonate, was synthesized by a proposed electrophilic ipso-substitution/reverse Friedel-Crafts alkylation of the lower-aromatic ring on 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl. This ligand was utilized in the palladium-catalyzed Heck alkynylation (copper-free Sonogashira coupling) of hydrophobic and hydrophilic aryl halides and terminal alkynes conducted in an aqueous acetonitrile solvent system. For the first time, an electron-deficient terminal alkyne, propiolic acid, was successfully coupled with aryl bromides. We also demonstrated that this catalyst is useful in the reaction of benzyl chlorides and terminal alkynes to provide benzyl alkynes in good yields. We show that by using an excess amount of base (> 1.0 equiv.) and higher reaction temperatures ( 80 °C), base-catalyzed isomerization to the corresponding aryl allenes can be achieved in a one-pot process. / by Kevin W. Anderson. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, June 2012. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references. / The THz polaritonics system is an on-chip platform for THz generation, detection, and control. THz-frequency electromagnetic waves are generated directly in a thin slab of lithium niobate crystal where they can be amplified and guided. Time-resolved phase-sensitive imaging lets us capture movies of THz waves as they propagate at the light-like speeds. I developed polaritonics methodologies and used the platform to study various microstructures interacting with THz waves. I began technique development by deriving a quantitative model explaining THz wave propagation in an anisotropic slab waveguide. From this model, I extracted the frequency-dependent wave velocity and used this knowledge to design an optical pumping geometry that phase-matches and coherently amplifies a selected THz frequency. This geometry can generate high-amplitude THz waves with a tunable center frequency and bandwidth. Much like the generation, the detection was also revamped. New optical designs, acquisition procedures, and hardware let us quantitatively measure THz field strengths. The image resolution was improved from ~50 [mu]m to 1.5 [mu]m, and measurement noise was reduced by 50-fold. Using the improved generation and detection methods, we studied two classes of microstructures: laser-machined air gaps and deposited metal antennas. Air gaps cut into the lithium niobate slab effectively reflect, waveguide, and scatter THz waves. We fabricated structures that demonstrate wave phenomena such as diffraction and interference and captured movies of THz waves interacting with these structures. The movies can be useful tools in lectures on electromagnetism because they beautifully illustrate the fundamental effects and bring cutting-edge research into the classroom. In addition to air structures, we studied metal antennas, which are interesting because of their ability to enhance optical fields and localize electromagnetic waves well below the diffraction limit. The polaritonics platform enabled incisive study of fundamental antenna behavior and scaling because we could map the antenna's near-field with [lambda]/100 spatial resolution and we could quantify large THz electric field amplitudes and enhancements in a deeply sub-wavelength gap between antennas. Antenna field enhancement is already facilitating nonlinear THz research, and the polaritonics platform will enable improved study of photonic systems such as metamaterials and photonic crystals. / by Christopher A. Werley. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 79-91). / This doctoral research has been defined by two main goals. The first has been to develop single colloidal quantum dot (QD) absorption as a new spectroscopic tool for investigating single QD electronic properties, dynamics, and inhomogeneities. In an important step towards achieving this goal, QDs were introduced into the field of optical trapping. Silica coated QDs were optically trapped using bowtie apertures in a thin silver film with low incident flux of 1.56 MW/cm 2 at 1064 nm. Additionally, QDs emitted upon trapping via two-photon excitation from the trapping laser due to strong field enhancement inside the aperture. The second goal of this research has been to investigate processes involved in single QD fluorescence intermittency, or blinking. Specifically, the transition from a nonemissive QD to an emissive QD was investigated using controlled amounts of thermal energy to drive recovery from photoinduced dimming in QD ensembles. Nonlinear thermal recovery was well described by a stretched exponential function, and further analysis yielded an underlying probability distribution of rate constants. Casting the rate constants as a collection of first-order activated processes provided an activation barrier probability distribution with significant density at room temperature thermal energy that peaks at 200 meV before decaying to zero. Progress towards single QD absorption using alternative nanoscale structures, including slot waveguides and circular apertures in silver film, is also discussed. Lastly, self-assembled cyanine-dye nanotubes were monitored during flash dilution with absorption spectroscopy at a high frame rate to separate spectroscopic contributions of the outer layer in double walled and bundled nanotubes. / by Russell Andrew Jensen. / Ph. D.

Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2017. / Vita. Scanning issues: Page 114 contains text that has been cropped/deleted from the right-side page margin. Appendix B section contains several graph pages with faint/illegible images. Cataloged from PDF version of thesis. / Includes bibliographical references. / I. Direct Observation of Intermediates Involved in the Interruption of the Bischler- Napieralski Reaction. The first mechanistic investigation of electrophilic amide activation of [alpha], [alpha]-disubstituted tertiary lactams and the direct observation of key intermediates by in situ FTIR, 1H, 13C, and 19F NMR in our interrupted Bischler-Napieralski based synthetic strategy to the aspidosperma alkaloids is described. Importantly, when considering base additives during electrophilic amide activation, more hindered c-quaternary tertiary lactams require the use of non-nucleophilic pyridine additives in order to avoid deactivation via a competing desulfonylation reaction. The isolation and full characterization of a tetracyclic iminium trifluoromethanesulfonate provided additional correlation between in situ characterization of sensitive intermediates and isolable compounds involved in this synthetic transformation. II. Total Synthesis of (+)-Fendleridine, (+)-Acetylaspidoalbidine, and (+)-Limaspermidine. An Tf2O-mediated electrophilic amide activation of a readily available C21-oxygenated lactam, followed by transannular cyclization and in situ trapping of a transiently formed C19-iminium ion, expediently provides access to the hexacyclic C19-hemiaminal ether alkaloids (+)- fendleridine, (+)-acetylaspidoalbidine, and (+)-limaspermidine. A highly effective enzymatic resolution of a non-[beta]-branched primary alcohol (E=22) allowed rapid preparation of both enantiomeric forms of a C21-oxygenated precursor for synthesis of these aspidosperma alkaloids. III. Development of an Ortho-Acetoxylation of Indoline Amides and its Application to the Total Synthesis of (+)-Haplocidine and (+)-Haplocine. The first total syntheses of (+)-haplocidine and its NI-amide congener (+)-haplocine is described. The concise synthesis of these alkaloids required the development of a late-stage and highly selective C-H oxidation of complex aspidosperma alkaloid derivatives. A versatile, amide directed ortho-acetoxylation of indoline amides enabled the implementation of a unified strategy for late-stage diversification of hexacyclic C19-hemiaminal ether structures via oxidation of the corresponding pentacyclic C19-iminium ions. / by Kolby Lyn White. / Ph. D. in Organic Chemistry