Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1987. / Includes bibliographies. / by Julie Ann Straub. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Raymond D. Hiley. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2002. / Vita. / Includes bibliographical references. / Our research over the last four years has been focused on the development of mild and general methods for conducting palladium-catalyzed carbon-carbon bond forming reactions utilizing the bulky and electron-rich trialkylphosphine, tri-tert-butylphosphine (P(t-Bu)3). We have concentrated on the utilization of aryl chlorides as substrates due to their lower cost and greater availability compared to traditionally employed aryl bromides, iodides, and triflates. The Suzuki reaction was the first reaction that we investigated, and we were able to develop a first-generation protocol for coupling aryl chlorides with aryl-boronic acids utilizing Pd2(dba)3/P(t-Bu)3 as catalyst and Cs2CO3 as base. A second-generation protocol utilizing KF as base offered significant improvements and provided an opportunity to expand the scope of the reaction. Electron-deficient aryl chlorides underwent Suzuki reaction at room temperature. Hindered substrates and unactivated vinyl chlorides could be coupled efficiently, and turnover numbers as high as 9,700 could be achieved. In addition, we discovered a highly unusual selective coupling of an aryl chloride in preference to an aryl triflate. The next reaction that we examined was the Heck reaction, and we were able to develop a method for coupling aryl chlorides with olefins using Pd/P(t-Bu)3 as catalyst and Cs2CO3 as base. A significant improvement in terms of scope and mildness of conditions was realized with the replacement of Cs2CO3 with Cy2NMe, which allowed for the coupling of sterically and electronically diverse aryl bromides at room temperature, as well as the first room-temperature Heck couplings of aryl chlorides. / (cont.) A wide variety of olefins could be employed in these couplings, including disubstituted olefins. In addition, these Heck reactions could be performed on multigram scale with minimal purification of starting materials, emphasizing the practicality and robustness of this method. Prior to 1999 there were no reports of palladium-catalyzed Stille couplings of unactivated aryl chlorides; utilizing Pd/P(t-Bu)3 in tandem with a fluoride activation strategy, we were able to develop the first general method for Stille couplings of aryl chlorides. More recently, we have considerably increased the scope of this reaction, including the synthesis of tetra-ortho-substituted biaryls, selective couplings of chlorides over triflates, and couplings of some aryl chlorides at room temperature. We have also undertaken mechanistic, kinetic, and reactivity studies using 1H NMR, P NMR, and GC. As a result of these studies, we believe that a monophosphine palladium species is the active catalyst in many of these couplings. The bisphosphine palladium complex Pd(P(t-Bu)3)2 is the resting state; yet by itself it is an ineffective catalyst for room-temperature couplings of aryl chlorides. The addition of phosphine-free Pd2(dba)3 to Pd(P(t-Bu)3)2 generates an efficient catalyst for room-temperature couplings and inspired us to try to utilize crystalline and now commercially available Pd(P(t-Bu)3)2 as a catalyst to eliminate the need to handle air-sensitive P(t-Bu)3. For the most part we have been quite successful in this regard; mixtures of Pd(P(t-Bu)3)2 and Pd2(dba)3 are efficient catalysts for many room-temperature couplings of aryl chlorides. ... / by Adam F. Littke. / Ph.D.

Thesis: Ph. D. in Physical Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Colloidal quantum dots (QDs) exhibit remarkable size-tunable optical properties including broad absorbance and bright, narrow emission. This thesis presents efforts to utilize, manipulate, and expand these properties. Despite the wide range of applications that benefit from multiband spectral information, traditional p-n junction photodetectors suffer from a fundamentally limited range of sensitivity due to a trade-off between light absorption and charge extraction. In order to expand the utility of a photodetector, its region of sensitivity can be enhanced via spectrum shifting. Here the optical properties of QDs are utilized to shift high energy photons to lower energy photons that lie within the detector's sensitive region through a process called luminescent downshifting. Chapters 2-5 will explore the application of luminescent downshifting from the near-ultraviolet to the short-wavelength infrared, the far-ultraviolet to the visible, and the ultraviolet to the mid-wavelength infrared. Unique challenges are addressed for each wavelength region to achieve increases of 10-55% absolute in the external quantum efficiency. The technology has been translated from single-element detectors to imaging arrays which is demonstrated in various environments. In pursuit of a deeper understanding of the surface-related effects on the photophysical properties of infrared quantum dots, the feasibility of shell growth and the effect of stoichiometric modification of lead chalcogenide quantum dots are presented in Appendix A. The resulting impact on emission wavelength, quantum yield, photoluminescent lifetime, and carrier mobility are explored. / by Jennifer Marie Scherer. / Ph. D. in Physical Chemistry

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2017. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references. / A molecular beam mass spectrometer (MBMS) has been constructed and upgraded with a laser desorption system. MBMS has allowed for the detection of reactive small molecules including but not limited to P₂ from P₂A₂ (where A = anthracene, C₁₄H₁₀), HCP from PPh₃(HCP)A and various dialkylamino phosphinidenes from their corresponding dibenzo-7-phosphanorbornadiene precursors by mass spectrometry. In cases where the desired reactive small molecule was not detected, MBMS has provided valuable information as to the degradation processes which may be occurring and has guided molecular precursor development. Through the use of highly sensitive microwave spectroscopic techniques, it was found that H₂S and N₂O₃ react to form the elusive molecule HSNO in the gas phase. HSNO is believed to be a crucial intermediate in biological signaling. Through isotopic labeling studies, an accurate structure of HSNO could be derived and subsequent degradation of the molecule was explored. The hexacarboxamide cryptand mBDCA-5t-H₆ was used as a ligand to prepare mono- and bimetallic iron complexes of the formula [Fe₂(mBDCA-5t)]²- and [Fe(mBDCA-5t-H³)]-. Both complexes were observed to react reversibly or irreversibly with CO or NO respectively to afford [(FeEO)-Fe(mBDCA-5t)]²- or [FeEO(mBDCA-5t-H₃)]- where E = C or N. Treatment of [(FeNO)·Fe(mBDCA-5t)]2- with excess NO resulted in the formation of [Fe₂O(mBDCA-5t)]²-, which could be independently prepared by treatment of [Fe₂(mBDCA-5t)]²- with the O-atom transfer reagent N-methylmorpholine N-oxide. The chemistry of peroxide dianion, in the form of the encapsulated complex [O₂[subset]mBDCA- 5t-H₆]²-, has been explored in nonaqueous media. In particular, [O₂[subset]mBDCA-5t-H₆]²- was demonstrated to react with CO gas at 40 °C over the course of several hours to furnish the encapsulated carbonate cryptate, [CO₃[subset]mBDCA-5t-H₆]²-. Through labeling studies, it was confirmed that the carbon of the carbonate was derived from CO. Treatment of [O₂[subset]mBDCA-5t-H₆]²- with CO₂ also affords [CO₃[subset]mBDCA-5t-H₆]²-, but with concomitant oxidation of the solvent. The oxidation of the solvent was found to proceed through the reactive oxidants -O₂COOCO²- and HOOCO₂- and sheds light on oxidative processes which may be occurring in lithium-air cells. Exposure of solid Li₂O₂ to gaseous p-benzoquinone results in the formation of a blue coating on Li₂O₂. This coating was identified as the quinone radical anion Li[p-C₆H₄O₂], which forms via lithium and electron transfer from Li₂O₂. This charge and ion transfer process results in the conversion of Li₂O₂ to LiO₂, a long-sought intermediate in the lithium-air community. / by Matthew Jordan Nava. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Chemistry, 2016. / Cataloged from PDF version of thesis. Vita. / Includes bibliographical references (pages 31-32). / Short linear [alpha]-olefins such as 1-butene are valuable commodity chemicals due to their use as comonomers in linear low-density polyethylene. Presently only homogeneous systems are used to catalyze ethylene dimerization in industry, causing many to suffer from quick deactivation and poor selectivity. The metal-organic framework (MOF) CPF-5 Mn₅(TBA)₃(HCOO)₃(OH)(H₂O₂)2]]₄·6DMF where TBA = 4-(l H-tetrazol-5-yl)benzoic acid provides an ideal structural template for the development of a heterogeneous catalyst for ethylene dimerization. Ni exchanged CPF-5 (Ni-CPF-5) treated with diethylaluminum chloride had a maximum turnover frequency of 23,000 mole ethylene per mole Ni per hour, and a maximum selectivity for 1-butene of 80% under optimized conditions. Ethylene pressure strongly influenced the activity and selectivity of Ni-CPF-5. Though the observed activity behavior is similar, the selectivity trends diverged significantly from previously reported MOF dimerization catalysts. / by Kathleen E. Martin. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011. / Vita. Cataloged from PDF version of thesis. / Includes bibliographical references. / Building blocks, containing majority fluorine content by weight, for PPEs and PPVs have been synthesized. Some of the monomers were shown to give exclusively fluorous-phase soluble polymers, the syntheses of which were achieved by fluorous biphasic polymerization conditions. Perfluoroalkylated PPEs were found to have excellent fluorescence quantum yields and photophysical and chemical stability, and were used to demonstrate their capability in sensing electron-rich aromatic systems via fluorescence quenching. Perfluoroalkylated PPVs were shown to have poor solubility in both fluorous and non-fluorous solvents. Furthermore, the polymer displayed extremely high stability. Utilizing the fluorous solubility of perfluoroalkylated PPE, fluorescent fluorocarbon-in-water emulsions were achieved. When perfluoroalkylated carboxylate was used as the surfactant, emulsions with surfaces that could be modified via amide-bond forming reactions were obtained. When tagged with biotin, these emulsions showed large degrees of aggregation in the presence of streptavidin. The final chapter of this thesis describes an amide-bond forming reaction to attach gold nanoparticles selectively to the termini of single-walled carbon nanotubes utilizing surfactants to protect the sidewalls of nanotubes. / by Jeewoo Lim. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2005. / Vita. / Includes bibliographical references. / (Trialkylsilyl)vinylketenes ("(TAS)vinylketenes") and (trialkylsilyl)arylketenes ("(TAS)- arylketenes") function as versatile four-carbon building blocks for the synthesis of carbocyclic and heterocyclic compounds. A new [4 + 1] annulation strategy for the synthesis of substituted 2-indanones, based on the reaction of TAS-arylketenes with trimethylsilyl diazomethane, has been developed. In addition, a new class of carbenoid reagents for our previously reported [4 + 1] cyclopentenone annulation has been identified. Studies have shown that the reaction of a- benzotriazolyl organolithium compounds (prepared via metallation of readily available N- substituted benzotriazole derivatives) with (TAS)vinylketenes generates dienolate intermediates which cyclize to form cyclopentenones. Most cases of the annulation proceed with a high level of diastereoselectivity, and deliver highly substituted and functionalized 2-silylcyclopentenones in good yield. Furthermore, the vinylsilane moiety incorporated in the [4 + 1] annulation products provides a useful handle for further synthetic transformations. Preliminary studies focused on elaboration of the cyclopentenone products have laid the groundwork for future applications of this [4 + 1] annulation methodology. / by Christopher P. Davie. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006. / Includes bibliographical references (leaf 36). / In preparation for performing a triple resonance experiment to study the Rydberg states of calcium monofluoride (CaF), a double resonance spectrum of formaldehyde will be recorded. A dye laser will populate a level in formaldehyde's first electronically excited state, and pure rotational transitions will be induced by applying a terahertz electric field. A terahertz spectrometer has been built for this purpose, and the principles of terahertz spectroscopy are described. The 4'0 vibronically allowed transition of the A1 A2 <-- X1A1 electronic transition was chosen for study. The dye laser will be tuned to 28307.13 cm'l (353.2679 nm) within this band in order to transfer population from the ... level in the ground state to the ... level in the excited state, according to b-type selection rules for electronic transitions. A Boltzmann distribution was used to determine that ... was the most populated state, and 50% of the molecules from this level will be transferred to the excited state. The new population differences created after electronic excitation will allow four rotational lines ... in the ground state, and ...in the excited state) to experience a significant gain in absorption coefficient compared to all other rotational transitions occurring in the ground state. These new absorption coefficients are calculated and compared against those for the ground state spectrum without electronic excitation, showing about a factor of 10 increase. The changes in the THz electric field as it propagates through the sample of formaldehyde are also described. / by Emily E. Fenn. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1989. / Vita. / Includes bibliographical references (leaves 182-190). / by Robert P. Short. / Ph.D.