Synthetic chemistry has played a pivotal role in the evolution of modern life. More recently, the emerging field of synthetic biology holds the promise to bring about a paradigm shift with designer microbes to renewably synthesize complex molecules in a fraction of the time and cost. Still, given synthetic chemistry’s superior parsing powers to access a greater number of unnatural end products and nature’s virtuosity at stitching a staggering palette of carbon frameworks with ease, a hybrid approach that leverages the respective strengths of the two fields could prove advantageous for the efficient production of valuable natural molecules and their analogs. In a first demonstration of the hybrid approach where the biosynthesized intermediate is not part of the target molecule’s biosynthetic pathway, we engineered E. coli to produce Z,E-farnesol, which we subsequently transformed into a library of novel analogs of the commercially important amber fragrance Ambrox®, including the first synthetic patchouli scent. In a second demonstration of the hybrid approach, we produced the valuable tocotrienols (vitamin E) from yeast-produced geranylgeraniol in a single step C–C coupling with concomitant regioselective cycloetherification of the most proximal vinyl of the polyene, the first such process of its kind. The novel acid catalyst system that allowed for this unique regioselective cyclization holds promise as an asymmetric proton transfer tool and could open the door to facile asymmetric synthesis of vitamin E and other molecules.

Lau Cheuk Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 93-98). / Abstracts in English and Chinese. / Table of Contents --- p.i / Acknowledgements --- p.iii / Abbreviations --- p.iv / Structural Abbreviations for Porphyrin Complexes --- p.v / Abstract --- p.vi / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- General Introduction --- p.1 / Chapter 1.2 --- Activation of Carbon-Hydrogen Bond (CHA) by Transition Metal --- p.2 / Chapter 1.2.1 --- Application of CHA by Transition Metals --- p.3 / Chapter 1.2.2 --- Thermodynamic in CHA by Transition Metals --- p.5 / Chapter 1.2.3 --- Types of Carbon-Hydrogen Activations --- p.6 / Chapter 1.3 --- Carbon-Hydrogen Bond Activation of Aldehydes --- p.14 / Chapter 1.3.1 --- Catalytic Application of CHA of Aldehydes by Transition Metals --- p.14 / Chapter 1.3.2 --- Stability of Intermediate M(COR) --- p.15 / Chapter 1.3.3 --- Issue in Selectivity --- p.16 / Chapter 1.4 --- Structural Features of Rhodium Porphyrins --- p.23 / Chapter 1.5 --- Objective of the work --- p.24 / Chapter Chapter 2 --- Carbon-Hydrogen Activation of Aldehydes by Rh(ttp)Cl and Rh(ttp)Me / Chapter 2.1 --- Introduction --- p.26 / Chapter 2.2 --- CHA of Aldehydes by Rh(ttp)Cl --- p.27 / Chapter 2.2.1 --- Preparation of Rh(ttp)Cl --- p.27 / Chapter 2.2.2 --- Solvents Screening --- p.27 / Chapter 2.2.3 --- Results and Discussion --- p.30 / Chapter 2.3 --- CHA of Aldehydes by Rh(ttp)Me --- p.33 / Chapter 2.3.1 --- Preparation of Rh(ttp)Me --- p.34 / Chapter 2.3.2 --- Results and Discussion --- p.35 / Chapter 2.4 --- Mechanistic Studies --- p.37 / Chapter 2.4.1 --- CHA of Aldehydes by Rh(ttp)Cl --- p.37 / Chapter 2.4.2 --- CHA of Aldehydes by Rh(ttp)R --- p.42 / Chapter 2.5 --- Comparison of the u(C=0) --- p.48 / Chapter 2.6 --- X-ray Data --- p.49 / Chapter 2.7 --- Summary --- p.50 / Chapter Chapter 3 --- CHA of Aldehydes by Rh(ttp)CH2CH2OH and Rh(ttp)+X- / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.2 --- CHA of Aldehydes by Rh(ttp)CH2CH2OH --- p.53 / Chapter 3.2.1 --- Results and Discussion --- p.53 / Chapter 3.2.2 --- Mechanistic Studies --- p.61 / Chapter 3.3 --- CHA of Aldehydes by Rh(ttp)+X- --- p.65 / Chapter 3.4 --- Summary --- p.67 / Conclusion --- p.68 / Experimental --- p.69 / Reference --- p.93 / Appendix I Crystal Data and Processing Parameters --- p.99 / List of Spectra --- p.141 / Spectra --- p.143

Base-promoted CHA of unstrained alkanes with 5,10,15,20-tetratolylporphyrinatorhodium complexes, Rh(ttp)X (X = Cl, H, Rh(ttp)), has been achieved. Rh(ttp)Cl, reacted with n-pentane, n-hexane, n-heptane, c-pentane and c-hexane in the presence of potassium carbonate at 120 °C in 6 to 24 h to give rhodium porphyrin alkyls, Rh(ttp)R, in 29--76% yields. Mechanistic investigations suggested that Rh 2(ttp)2 and Rh(ttp)H are key intermediates for the parallel CHA step. The roles of base are (i) to facilitate the formation of Rh(ttp)Y (Y- = OH-, KCO3 -), (ii) to enhance the CHA rate with alkane and generate Rh(ttp)H by a Rh(ttp)Y species which is more reactive than Rh(ttp)Cl, and (iii) to provide a parallel CHA pathway by Rh2(ttp)2. / c-Octane reacted with Rh(ttp)Cl at 120 °C in 7.5 h in the presence of K2CO3 to yield Rh(ttp)( n-octyl) and Rh(ttp)H in 33% and 58% yields, respectively. Mechanistic investigations indicate that the CCA product is generated from the Rh II(ttp)-catalyzed 1,2-addition of c-octane with Rh(ttp)H. Reaction of c-octane and Rh(ttp)H/Rh2(ttp) 2 (10:1) selectively yielded Rh(ttp)(n-octyl) in 73% at 120 °C in 15 h. The catalyst RhII(ttp) radical cleaves the C-C bond of c-octane to form to a Rh(ttp)-alkyl radical, which then abstracts a hydrogen atom from Rh(ttp)H to generate the Rh(ttp)( n-octyl), and subsequently leading to regeneration of the Rh II(ttp) radical. (Abstract shortened by UMI.) / K2CO3-promoted CHA of the ring-strained cycloheptane with Rh(ttp)Cl at 120 °C in 6 h gave the CHA product Rh(ttp)( c-heptyl) and together with, unexpectedly, the CCA product Rh(ttp)Bn, in 30% and 24% yields, respectively. Mechanistic studies revealed that Rh(ttp)( c-heptyl) undergoes beta-hydride elimination in neutral condition or beta-proton elimination in basic condition followed by reprotonation to give rhodium(III) porphyrin hydride, Rh(ttp)H, and c-heptene. Successive base-promoted CHA of c-heptene with Rh(ttp)H, followed by beta-proton elimination, generates cycloheptatriene. The CHA of cycloheptatriene with Rh(ttp)H formed Rh(ttp)(c-heptatrienyl), which underwent rearrangement with carbon-carbon cleavage at 120 °C in 16 d to yield Rh(ttp)Bn in 96% yield. / The objectives of this research focus on the investigation of carbon-hydrogen bond activation (CHA) and carbon-carbon bond activation (CCA) of alkanes by rhodium porphyrin complexes as well as the mechanistic understanding. / Chan, Yun Wai. / Adviser: Kin Shing Chan. / Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Chapter 1 provides the general review of phosphoranoimines and 1-azaallyls as ligands for group 4 and 14 metal complexes. / Chapter 2 describes the development of low-valent group 14 1,3-dimetallacyclobutanes from phosphoranoimines. Three low-valent 1,3-distannacyclobutanes 1,3-[Sn{C(Pr i2P=NSiMe3)(2-Py)}]2 ( 95), 1,3-[Sn{C(Ph2P=NSiMe3)(C6H 5)}]2 (97) and 1,3-[Sn{C(Ph2P=NSiMe 3)(PPh2)}]2 (100) were synthesized from the phosphoranoimine ligands [CH2(Pri 2P=NSiMe3)(2-Py)] (92), [CH2(Ph 2P=NSiMe3)(C6H5)] (96) and [CH2(Ph2P=NSiMe3)(PPh 2)] (99), respectively. A novel cationic tin(IV) species [HC(Pri2P=NSiMe3)(Ar)] -[SnCl3]+ (Ar = 9-anthryl) ( 104) was synthesized from [CH2(Pri 2P=NSiMe3)(Ar)] (Ar = 9-anthryl) (103). / Chapter 3 describes the reactivies of low-valent group 14 1,3-distannacyclobutanes (95 and 111) and the isolation of the enantiomers of 95 and [1-Sn{C(Pri2P=NSiMe 3)(2-Py)}3-Pb{C(Pri2P=NSiMe 3)(2-Py)}] (120). The reactions of 95 or 111 with M(CO)5(THF) (M = Cr, Mo, W), CpMn(CO)2THF (Cp = eta-C5H5), MeI and Br2 were performed. Three isomers of compound 95 (95R, 95S and 95I) and two enantiomers of compounds 120 ( 120R and 120S) and 122 (122R and 122S) were obtained by the method of recrystallization from different solvents. Heteroleptic lead(II) compound [{(Pri 2P=NSiMe3)(2-Py)CH}Pb{N(SiMe3)2} 2] (121) was synthesized, which further react with 94 to give 1,3-[Pb{C(Pri2P=NSiMe 3)(2-Py)}]2 (122). / Chapter 4 describes the development of group 4 metal complexes from phosphoranoimines. Group 4 metal imido complexes [(Me2N)2M{CH(Ph2 PN)(2-Py)}]2 (M = Zr (133), Hf (134)) and ionic compounds [ML2Cl]+2[MCl 6]2- (L = {CH(R2PNSiMe3)(2-Py)}) (135 M = Zr, R = Ph, 136 M = Hf, R = Ph, 137 M = Zr, R = Pri, 138 M = Hf, R = Pri) were synthesized. The neutral zirconium(IV) dichloride compound [ZrCl2{CH(Ph2P=NSiMe 3)(C6H5)}2] (139) was prepared by the reaction of lithium compound [(THF)2Li{CH(Ph 2PNSiMe3)(C6H5)}] (97) with ZrCl4. The catalytic activity of the compounds toward ethylene polymerization has been investigated. / Chapter 5 describes the development of group 4 metal complexes from 1-azaallyls. Lithium cyclohexenyl-1-azaallyl compound [(TMEDA)LiN(SiMe3)C(Ph)= CHCHC&parl0;SiMe3&parr0;CH2CH 2C H2] (149) and zirconium(IV) dichloride compound [Zr{N(SiMe3)C(Ph)(L)}2Cl2] (L = CHCHC&parl0;SiMe3&parr0;CH2CH 2C H2) (150) were synthesized. Novel anionic one-dimensional bifunctional lithium compound [{(THF)Li(N(SiMe3))2C}(CN)C 6H4-1,4)]n (151) has also been synthesized. Similar reactions of 1,2-dicyanobenzene, 1,3-dicyanobenzene or 1,4-dicyanobenzene with lithium amide [(Et2O)2LiN(SiMe3) 2] afforded lithium bis(1,3-diazaallyl) compounds [{(THF)2Li(N(SiMe 3))2C}C6H4-1,2)] (152), [{(THF)2Li(N(SiMe3))2C}C6H 4-1,3)] (153) and [{(THF)2Li(N(SiMe3)) 2C}C6H4-1,4)] (154), respectively. / The work presented in this thesis is mainly focused in two parts: (i) the synthesis and reactivities of low-valent main group 14 metal complexes derived from phosphoranoimines, (ii) the synthesis and catalytic studies of transition group 4 metal complexes derived from phosphoranoimines and 1-azaallyl ligands. / Wong Kam Wing. / "December 2006." / Adviser: Kevin Wing-Por Leung. / Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5233. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

This thesis describes expansion of the ability of isothioureas to act as organocatalysts in formal [2+2]-, [3+2]- and [4+2]-cycloadditions between carboxylic acids and various acceptors via Type I ammonium enolate intermediates. Chapter 2 describes the optimisation and investigation of [2+2]-cycloadditions from ammonium enolates and N-sulfonylimines as the two components. The development of this methodology allows successful access to highly stereodefined β-lactams and, following in situ ring-opening, β-aminoesters. The products are obtained from either preformed homoanhydrides or directly from carboxylic acids, using open flask conditions, from simple, bench-stable starting materials and is scalable. A variety of anti-β-lactams (21 examples, 46-68% yield, up to >95:5 dr, 21->99% ee) and β-aminoesters (9 examples, 44-74% yield, up to >95:5 dr, 68-92% ee) were accessed in moderate yield, excellent diastereo- and good enantioselectivity. This represents an improved route to anti-β-lactams over previously described ketene and N-triflyl imine based methods. Chapter 3 subsequently describes studies focussed on the use of ester surrogates in the formal [4+2]-cycloaddition reactions of isothiourea generated Type I ammonium enolates. Iso-propylphosphonate 163 proved highly effective as the four-component in this process, which following the in situ ring-opening of the initial dihydropyranone product allowed isolation of a range of novel diester products which were previously unobtainable using this methodology. The products were accessed in moderate to excellent yields, excellent diastereo- and enantiocontrol (9 examples, 12-63% yield, up to >95:5 dr, 67-99% ee) with this process also amenable to a large scale. Furthermore, selective reduction and acid-catalysed cyclisation allowed access to δ-lactone products in good yield with retention of stereocontrol. Finally, Chapter 4 describes work on isothiourea-catalysed formal [3+2]-cycloadditions of oxaziridines and acetic anhydrides gave access to stereodefined five-membered oxazolidin-4-one heterocycles. In this case, the use of preformed homoanhydrides and an inorganic base was imperitive to avoid reduction of the oxaziridine starting material. The oxazolidin-4-one products could be accessed in excellent yield and ee however poor dr (13 examples, 63-96% yield, up to 59:41 dr anti:syn, up to >99% ee for both diastereoisomers). Following isolation, reduction of these heterocycles allowed access to enantioenriched diols with little loss in stereocontrol. Mechanistic analysis has shown that an improvement in diasterocontrol can be obtained by the use of an enantioenriched oxaziridine, demonstrating the stereospecificity of this process.

本論文主要研究銥和銠卟啉絡合物與鹵代苯 (ArX, X = Cl, Br, I)的碳-鹵鍵(Ar-X)的斷裂反應及其應用。本論文分為四個部分：（1）銠卟啉絡合物與鹵代苯(ArX, X = Cl, Br, I)之間的碳-鹵鍵(Ar-X)斷裂反應；（2）氟氯化苯的碳-氟鍵(Ar-F)與碳-氯鍵(Ar-Cl)斷裂的競爭反應；（3）氟取代基對金屬（銥和銠）-芳香碳(M-Ar)鍵強弱的影響；以及（4）銥卟啉氟硼荧絡合物的合成。 / 第一部分闡述了銠卟啉絡合物(Rh(ttp)Cl)與鹵代苯(ArX, X = Cl, Br, I) 之間的碳-鹵鍵 (Ar-X) 斷裂反應以及反應機理。在鹼性條件下，無論富電子還是缺電子的鹵代苯都能與Rh(ttp)Cl反應，生成Ar-X鍵斷裂的產物──銠卟啉芳基絡合物(Rh(ttp)Ar) 。機理研究顯示， Rh(ttp)Cl 首先與氫氧根離子反應生成Rh(ttp)OH，進而通過二聚反應生成[Rh(ttp)]₂。[Rh(ttp)]₂在加熱條件下與Rh(ttp)自由基可以互相轉化，產生的Rh(ttp)自由基與鹵代苯進行原位取代反應，生成銠卟啉芳基絡合物(Rh(ttp)Ar)和鹵素自由基。鹵素自由基可以和另一個Rh(ttp)自由基反應生成Rh(ttp)X，在氫氧根離子存在的條件下，Rh(ttp)X將再次轉化為Rh(ttp)OH繼續反應。 / 第二部分描述了氟氯化苯中碳-氟鍵(Ar-F)與碳-氯鍵(Ar-Cl)斷裂的競爭反應。機理研究顯示碳-氟鍵(Ar-F)斷裂的中間體是M(por)⁻，而碳-氯鍵(Ar-Cl)斷裂的中間體是MII(por)。因此，我們可以通過改變反應條件而控制生成物。例如，在較低溫度下和強鹼性的極性溶劑中，以M(por)⁻前體作為反應物，可以獲得較多的碳-氟鍵(Ar-F)斷裂的產物；而在較高溫度下和弱鹼性的非極性溶劑中，可以獲得較多的碳-氯鍵(Ar-Cl)斷裂的產物。 / 第三部分敘述了間位氟取代基對金屬-芳香碳(M-Ar)鍵的增強作用。有間位氟取代基的金屬（銥，銠）卟啉芳基絡合物(M(ttp)ArF)是最穩定的同分異構體。在250°C條件下，當反應30天後，Ir(ttp)C₆H₄F的三個異構體達到平衡狀態，其鄰位:間位:對位的比例大約為0:5:1。理論計算的結果也顯示Ir(ttp)(3-fluorophenyl)相對Ir(ttp)(2-fluorophenyl)和Ir(ttp)(4-fluorophenyl)有更低的能量。氟取代基在鄰位時，氟與卟啉之間空間位阻較大，減弱了金屬-芳香碳(M-Ar)鍵的鍵能。與氟取代基在對位相比，在間位時具有更好的吸電子效應，從而增加了金屬-芳香碳(M-Ar)鍵的極性，增強了金屬-芳香碳(M-Ar)鍵鍵能。 / 第四部分描述了利用碳-鹵鍵 (Ar-X) 的斷裂，合成銥卟啉氟硼荧絡合物的反應。銥卟啉氟硼荧絡合物的產率可以達到70%。銥卟啉氟硼荧絡合物在生物成像和放射療法都有潛在的應用。銥卟啉氟硼荧絡合物是用金屬自由基與氟硼荧反應合成的。 / This thesis focuses on the reaction scopes, mechanistic investigations and applications of base-promoted aryl carbon-halogen (Ar-X) bond cleavage with iridium and rhodium porphyrin complexes. This thesis is divided into four parts: (1) Ar-X (X = Cl, Br, I) bond cleavage with Rh(ttp)Cl; (2) competitive Ar-F and Ar-Cl bond cleavage with iridium and rhodium porphyrins; (3) fluorine substituent effect on the M-Ar (M = Ir, Rh) bond strength; and (4) synthesis of iridium porphyrin BODIPY complexes. / Part I describes the reaction scopes and mechanism of Ar-X (X = I, Br, Cl) bond cleavage with Rh(ttp)Cl (ttp = 5,10,15,20-tetratolylporphyrinato dianion). Under basic conditions, both electron-rich and electron-deficient ArX undergo Ar-X bond cleavage to give Rh(ttp)Ar in good yields. [with diagram] / The mechanistic investigations suggest that RhIII(ttp)Cl first undergoes ligand substitution by OH- to give RhIII(ttp)OH, which forms [RhII(ttp)]₂ through reductive dimerization. RhII(ttp) radical, which is in equilibrium with [RhII(ttp)]₂, cleaves the Ar-X (X = I, Br, Cl) bond through metalloradical ipso-substitution and gives RhIII(ttp)Ar and X radical. X radical recombines with another RhII(ttp) radical to generate RhIII(ttp)X, which gives back RhIII(ttp)OH through ligand substitution by OH-. [with diagram] / Part II describes the competitive Ar-F and Ar-X (X = Cl, Br) bond cleavage reactions of fluorochlorobenzenes with iridium and rhodium porphyrin complexes. Mechanistic studies suggest that M(por)⁻ is the intermediate for the Ar-F bond cleavage while MII(por) is the intermediate for the Ar-X bond cleavage. By taking advantage of the difference in mechanisms of the Ar-F and Ar-X bond cleavages, the selectivity of bond cleavage can be controlled by varying the reaction conditions. The Ar-F bond cleavage is favored in a polar solvent with a stronger base at lower temperatures with M(por)⁻ precursor, and the Ar-X bond cleavage is favored under non-polar conditions with a weaker base and at higher temperatures. [with diagram] / Part III describes the meta-fluorine substituent effect on strengthening the M-Ar (M = Ir, Rh) bond of M(ttp)ArF. M(ttp)ArF with meta-fluorine substituent are the most stable isomers among the isomeric Ar-H bond cleavage products. At 250 °C for 30 days, the three isomers of Ir(ttp)C₆H₄F reached an equilibrium with o : m : p = 0 : 5 : 1. The theoretical calculations also suggest that Ir(ttp)(3-fluorophenyl) is of lower energy than Ir(ttp)(2-fluorophenyl) and Ir(ttp)(4-fluorophenyl). The ortho-fluorine substituent exhibits steric effect which weakens the M-Ar bond. The meta-fluorine, which is more electron-withdrawing than para-fluorine, enhances the polarity of the M-C(ipso) bond and thus strengthens the M-Ar bond. [with diagram] / Part IV describes the application of Ar-I bond cleavage with Ir(ttp)(CO)Cl in synthesizing iridium porphyrin boron-dipyrromethene (BODIPY) complexes, which are potential photosensitizers for biological imaging and photodynamic therapy. The clinically interested iridium porphyrin BODIPY complexes have been prepared by a radical process of metalloradical with BODIPY. [with diagram] / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Qian, Yingying. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references. / Abstracts also in Chinese.

by T.W. Chui. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 79-81). / Text in English; abstract also in Chinese. / by T.W. Chui. / Titleage --- p.i / Acknowledgments --- p.ii / Abstract --- p.iii / Table of contents --- p.v / Chapter Chapter 1 --- Introduction --- p.1 / Figure Captions --- p.16 / Chapter Chapter 2 --- Meauserment of first hyperpolarizability / Chapter 2.1 --- Electric Field Induced Second Hamonics (EFISH) --- p.21 / Chapter 2.2 --- Hyper-Rayleigh Scattering (HRS) --- p.23 / Chapter 2.3 --- Internal reference method and External reference method --- p.26 / Figure Captions --- p.28 / Chapter Chapter 3 --- Experimental Setup / Chapter 3.1 --- Design of experimental setup --- p.30 / Chapter 3.2 --- Alignment --- p.32 / Chapter 3.3 --- ower --- p.33 / Chapter 3.4 --- Samples --- p.33 / Figure Captions --- p.35 / Chapter Chapter 4 --- Measurement of first hyperpolarizability of selected molecules / Chapter 4.0 --- Introduction --- p.40 / Chapter 4.1 --- Result of spectral study of the scattered signal from CV --- p.43 / Chapter 4.2 --- Result of the first hyperpolarizability of CV --- p.46 / Chapter 4.3 --- HRS measurement with DANS --- p.47 / Figure Captions --- p.51 / Graphs --- p.52 / Tables --- p.57 / Chapter Chapter 5 --- Studies of the depolarization ratio of HRS and fluorescence light from CV / Chapter 5.0 --- Introduction --- p.59 / Chapter 5.1 --- Experimental setup for the measurement of depolarization ratio --- p.60 / Chapter 5.2 --- Measurement of depolarization ratio forNA at 532nm --- p.61 / Chapter 5.3 --- Measurement of depolarization ratio for CV at 532nm --- p.62 / Chapter 5.4 --- Measurement of depolarization ratio for fluorescence light from CV --- p.63 / Figure Captions --- p.68 / Graphs --- p.71 / Tables --- p.75 / Chapter Chapter 6 --- Conclusions --- p.77 / References --- p.79

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

Stable radicals have enjoyed widespread use in a variety of fields including synthetic chemistry, materials chemistry, energy storage, and biochemistry. This thesis outlines our investigations of cyclopropenium-based stable radicals and their application as redox mediators, redox-active ligands, catalysts, and materials for energy storage. The first chapter gives a brief overview of the use of radicals in synthetic chemistry. The principles that govern the stability of radicals is discussed and notable examples are highlighted. The second section of the first chapter reviews the aromatic platforms that have been developed by the Lambert group and how they might be converted into stable radical species. The second chapter details our study of 2,3-diaminocyclpropenones as stable radicals. These electron rich cyclopropenium derivatives undergo facile oxidation to yield a radical cation species. The origin of the stability of this oxygen-centered radical was elucidated by density functional theory calculations and analysis of the crystal structure. Diaminocyclopropenones were also found to be effective neutral L-type ligands in Ce(IV) complexes. EPR and UV-VIS experiments revealed that these complexes exhibited reversible homolytic dissociation of their diaminocyclopropenone ligands. The third chapter describes the use of trisaminocyclopropeniums as catholytes for nonaqueous redox flow batteries. A newly designed trisaminocyclopropenium structure could be accessed in large quantities and showed long lasting stability in its oxidized state. A new composite polyionic material was developed for use as a membrane suitable for organic solvent and high voltages. Cycling in combination with a perylenediimide anolyte yielded a 1.7 V battery that exhibited excellent coulombic efficiency and capacity retention. Using a spiro-bis(phthalimido) anolyte afforded a battery with an open circuit voltage of 2.8 V. The fourth chapter details how our battery studies with trisaminocyclopropenium radical dications led us to discover their photoinduced reactivity. We developed an electrophotocatalytic platform using trisaminocyclopropeniums as a species capable of being activated by both photochemical and electrochemical energy. The excited state oxidation potential of the doubly activated species was found to be +3.33 V, which was capable of effecting oxidative coupling reactions using both arenes and ethers as substrates. Density functional theory calculations and spectroscopic experiments revealed that the photoreactivity was due to a SOMO-inversion event. The trisaminocyclopropenium radical dication could be prepared on scale via direct electrolysis and subsequently used in high throughput screening.

No description available.