http://hdl.handle.net/1721.1/7794 http://hdl.handle.net/1721.1/17743 Fluorescence-based detection methodologies for nitric oxide using transition metal scaffolds Hilderbrand, Scott A. (Scott Alan), 1976- Chapter 1. Fluorescence-Based Detection Methodologies for Nitric Oxide: A Review. Chapter 2. Cobalt Chemistry with Mixed Aminotroponimine Salicylaldimine Ligands: Synthesis, Characterization, and Nitric Oxide Reactivity. Chapter 3. Carboxylate-Bridged Dimetallic Complexes as Potential Nitric Oxide Sensors. Chapter 4. Dirhodium Tetracarboxylate Scaffolds as Reversible Fluorescence- Based Nitric Oxide Sensors. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004. MIT Institute Archives copy has p. 191-192 bound between p. 188 and p. 189. Vita. Includes bibliographical references. Wed, 29 Oct 2003 22:58:59 GMT http://hdl.handle.net/1721.1/12465 A synthetic attack on the oestrone problem Woodward, R. B. (Robert Burns), 1917-1979 Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1937. Vita. Includes bibliographical references (leaves [53]-[54]). Thu, 29 Oct 1936 22:58:59 GMT http://hdl.handle.net/1721.1/41722 Organic materials with acenoid and iptycene structures Chen, Zhihua, Ph. D. Massachusetts Institute of Technology Chapter 1. The synthesis of a group of alkoxy-substituted para-acenequinones and their photophysical properties in solution and liquid crystal are reported. Polarized absorption and fluorescence measurements demonstrate that these acenequinones have excellent alignment with nematic LC hosts, indicating their potential as dichroic dyes for guest-host liquid crystal displays. In addition, the sensitivity of emission to the substitution allows the tuning of emission by functionalization of the acenequinone chromophore. Chapter 2. The synthesis of a series of fluorine- and alkyl/alkoxy-functionalized tetracenes using N-methyl-1,2,4,5-tetrafluoroisoindole as a synthetic building block is reported. The incorporation of fluorine functionalities was found to induce significant face-to-face molecular n-stacking in their crystal structures. Electrochemical behaviors and UV-vis absorbance spectroscopy results of these materials are also discussed. It was demonstrated that the substitution of alkyl/alkoxy groups on the main chain not only provided better solubility in common organic solvents, but also subtly tuned the crystal structures and electrochemical behaviors. Chapter 3. A self-polymerizable AB-type monomer for Diels-Alder (D-A) polymerization was prepared, and its polymerization was carried out in the melt phase and at high pressure in solution. The former method generated only low molecular weight polymer, but the latter one offered an efficient polymerization with increased molecular weight, due to the effect of high-pressure on reactions with a negative activation volume. A pyridinium p-toluenesulfonate catalyzed dehydration reaction of the D-A polymer led to a novel aromatic ladder polymer, poly(iptycene), which is soluble in common organic solvents and stable up to 350 oC. (cont.) The NMR and UV-vis spectra of these polymers match the spectra of their corresponding model compounds, and their synthesis is also reported. Chapter 4. Two diamino functionalized iptycene monomers were successfully synthesized via two synthetic routes: a direct nitration of triptycene followed by a reduction with hydrazine and D-A reaction between a benzo-fused 1,4-endoxide and 2,6-diaminoanthracene followed by a strong acid catalyzed dehydration. Their applications in the synthesis of novel triptycene-containing polyimides and polyureas were investigated and the resulting polymers were characterized by NMR, FT-IR, and UV-vis absorption spectroscopy. Chapter 5. Iptycene type quinoxaline and thienopyrazine monomers were successfully synthesized via a condensation between 10-dihydro-9,10-ethanoanthracene-11,12-dione and the corresponding diamines. Copolymers based on fluorene and these new iptycene monomers were prepared via Suzuki coupling reaction, and they exhibited good solubility in appropriate organic solvents. These copolymers are fluorescent both in solution and the solid state, emitting blue, greenish-blue, and red color, due to the electronic properties of the iptycene comonomers. The difference in their absorption and emission spectra was attributed to the donor-acceptor charge transfer interactions and/or polymer backbone conformation change induced by steric effects. Moreover, the spectroscopic data clearly demonstrated the insulating effect of iptycene units, which prevented the aggregation of the polymer chains and formation of excimers in the solid state. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007. Includes bibliographical references. Sun, 29 Oct 2006 22:58:59 GMT http://hdl.handle.net/1721.1/41556 Dioxygen activation and substrate hydroxylation by the hydroxylase component of toluene/O-xylene monooxygenase from pseudomonas sporium OX1 Murray, Leslie Justin Non-heme carboxylate-bridged diiron centers in the hydroxylase components of the bacterial multicomponent monooxygenases activate dioxygen at structurally homologous active sites. Catalysis requires the management of four substrates: electrons, protons, dioxygen, and hydrocarbons. Protein component complexes control the delivery of these substrates to the diiron center in the hydroxylase ensuring selective hydrocarbon oxidation. A detailed mechanistic understanding of structural and chemical consequences of such interactions is a significant challenge. This thesis begins with an overview of our current understanding of these processes. The discussion is primarily on the methane monooxygenase systems (MMO) because these have been the most extensively studied BMMs to date. Recent results for the toluene/o-xylene monooxygenase (ToMO) and phenol hydroxylase systems from Pseudomonas sporium OX1 are also briefly summarized, the former being the research focus of this dissertation. Restricting access to the diiron center in ToMOH and other non-heme carboxylate-bridged diiron proteins was proposed to facilitate observation of oxygenated intermediates. To examine this hypothesis, dioxygen activation in ToMOH mutants that were predicted to occlude this channel was investigated by rapid-freeze quench (RFQ) EPR, Mossbauer, and ENDOR spectroscopy and stoppedflow optical spectroscopy. For the I100W mutant, a transient species is observed with an absorption maximum at 500 nm. EPR and Mossbauer spectra of RFQ samples identified this species as a diiron(III,IV) cluster spin-coupled to a neutral W radical. ENDOR spectra of this intermediate confirmed the protonation state and type of the amino acid radical and also identified a labile terminal water or hydroxide on the diiron center. (cont.) Decay of this intermediate results in hydroxylation of the W radical. A diamagnetic precursor to the mixed-valent diiron(III,IV) center was also observed at an earlier time-point, with Mossbauer parameters typical of high-spin FeIII. We have tentatively assigned this antiferromagnetically-coupled diiron(III) intermediate as a peroxo-bridged cluster. A similar diiron(III) species is observed in RFQ Mossbauer samples from the reaction of reduced wild type hydroxylase with dioxygen. Substrate accelerates the decay rate of this species, providing evidence for the diiron(III) transient as the active oxidant. Under steady state conditions, hydrogen peroxide was generated in the absence of substrate. The oxidized hydroxylase also decomposed hydrogen peroxide to liberate dioxygen if no reducing equivalents were present. This catalase activity suggests that dioxygen activation could be reversible. The linear free energy relationship determined from steady state hydroxylation of para substituted phenols has a negative slope. A value of ? < 0 is indicative of electrophilic attack on the aromatic substrate by the oxidizing diiron(III) intermediate. The results from these steady state and pre-steady experiments provide compelling evidence that the diiron(III) transient is the active oxidant in ToMO and is a peroxodiiron(III) transient, despite differences between the optical and Mossbauer spectroscopic parameters and those of other peroxodiiron(III) centers. Enzymatic oxidation of the radical clock substrate probe, norcarane, by ToMO gives rise to both desaturation and hydroxylation products, norcarenes and norcaranols respectively. (cont.) Norcarenes are better substrates for this enzyme system than norcarane, producing additional oxidation products. In all, more than twenty oxidation products were characterized in these reaction mixtures, half of which arose from norcarene oxidation. Accounting for these secondary oxidation products, we determined that no substrate radical intermediates with a significant lifetime (t < 25 ps) are formed during catalysis. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. MIT Institute Archives copy includes accompanying CDROM with copy of thesis in .pdf format. "September 2007." Vita. Includes bibliographical references. 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