FT-IR and MAS NMR analysis of montmorillonite K10 supported MF2 reagents and their activity as catalysis /

ZnF2, CdF2, and CUF2 have been adsorbed onto the surface of montmorillonite K10, and the infrared and 19F, 27 AI, and 29Si MAS NMR spectra of the reagents over a range of loadings have been obtained. CUF2 was observed to attack the Si02 layer and form the complex CuSiF6, Zn F2 tends to attack the aluminium oxide layer, in which Zn isomorphously replaces AI, and forms AIF3 and AIF4 - complexes. All the spectroscopic evidence ruled out the formation of any AI-F and/or Si-F free species as CdF2 is adsorbed on the surface of montmorillonite K10. The reactivity of MF2-K10 reagents towards Friedel-Crafts benzylation of benzene with benzyl chloride varied from one reagent to another. ZnF2-K10 was observed to be the most reactive and CUF2 was the least reactive.

A G. C./M. S. study of the reaction and decomposition products of pentafluorophenyl-grignard and lithium reagents

Decomposition and side reactions of, and the synthetic use of, pentafluorophenylmagnesium bromide and pentafluorophenyllithium have been investigated using G,C9/M.S, techniques• Their reactions with reagents such as CgF^X (X - H, F, CI, Br, 1), C6F4X2 (X - H, CI)f C6F3C13, C6H6. (CgX5)3P (X = H, F), (C6X5)3P=0 (X = H, F), (CgX5)Si (CH3)3 (X = H, F) and (CH0K SiCl , n = 1,2, in ether or ether/n-hexane were studied• In addition to the principal reaction of synthetic use, namely the replacement of a halogen by a pentafluorophenyl group, two types of side reactions were observed* These were (i) intermolecular loss of LiF via a nucleophilic substitution, and (ii) intramolecular loss of LiF, followed by the addition of either inorganic salts such as lithium or magnesium halides, or organometal compounds such as organolithium or organo-Grigaard* G.C«/M.S. techniques were routinely employed to study complicated reaction mixtures. Although mass spectrometry alone has disadvantages for the identification of isomers, deduction of the most probable pathway often helps overcome this problem.

Investigation of single tryptophan proteins encapsulated in TEOS-derived sol-gel matrices by fluorescence spectroscopy /

In the work reported here, optically clear, ultrathin TEOS derived sol-gel slides which were suitable for studies of tryptophan (Trp) fluorescence from entrapped proteins were prepared by the sol-gel technique and characterized. The monitoring of intrinsic protein fluorescence provided information about the structure and environment of the entrapped protein, and about the kinetics of the interaction between the entrapped protein and extemal reagents. Initial studies concentrated on the single Trp protein monellin which was entrapped into the sol-gel matrices. Two types of sol-gel slides, termed "wet aged", in which the gels were aged in buffer and "dry-aged", in which the gels were aged in air , were studied in order to compare the effect of the sol-gel matrix on the structure of the protein at different aging stages. Fluorescence results suggested that the mobility of solvent inside the slides was substantially reduced. The interaction of the entrapped protein with both neutral and charged species was examined and indicated response times on the order of minutes. In the case of the neutral species the kinetics were diffusion limited in solution, but were best described by a sum of first order rate constants when the reactions occurred in the glass matrix. For charged species, interactions between the analytes and the negatively charged glass matrix caused the reaction kinetics to become complex, with the overall reaction rate depending on both the type of aging and the charge on the analyte. The stability and conformational flexibility of the entrapped monellin were also studied. These studies indicated that the encapsulation of monellin into dry-aged monoliths caused the thermal unfolding transition to broaden and shift upward by 14°C, and causedthe long-term stability to improve by 12-fold (compared to solution). Chemical stability studies also showed a broader transition for the unfolding of the protein in dry-aged monoliths, and suggested that the protein was present in a distribution of environments. Results indicated that the entrapped proteins had a smaller range of conformational motions compared to proteins in solution, and that entrapped proteins were not able to unfold completely. The restriction of conformational motion, along with the increased structural order of the internal environment of the gels, likely resulted in the improvements in themial and long-term stability that were observed. A second protein which was also studied in this work is the metal binding protein rat oncomodulin. Initially, the unfolding behavior of this protein in aqueous solution was examined. Several single tryptophan mutants of the metal-binding protein rat oncomodulin (OM) were examined; F102W, Y57W, Y65W and the engineered protein CDOM33 which had all 12 residues of the CD loop replaced with a higher affinity binding loop. Both the thermal and the chemical stability were improved upon binding of metal ions with the order apo < Ca^^ < Tb^"^. During thermal denaturation, the transition midpoints (Tun) of Y65W appeared to be the lowest, followed by Y57W and F102W. The placement of the Trp residue in the F-helix in F102W apparently made the protein slightly more thermostable, although the fluorescence response was readily affected by chemical denaturants, which probably acted through the disruption of hydrogen bonds at the Cterminal end of the F-helix. Under both thermal and chemical denaturation, the engineered protein showed the highest stability. This indicated that increasing the number of metal ligating oxygens in the binding site, either by using a metal ion with a higher coordinatenumber (i.e. Tb^*) which binds more carboxylate ligands, or by providing more ligating groups, as in the CDOM33 replacement, produces notable improvements in protein stability. Y57W and CE)OM33 OM were chosen for further studies when encapsulated into sol-gel derived matrices. The kinetics of interaction of terbium with the entrapped proteins, the ability of the entrapped protein to binding terbium, as well as thermal stability of these two entrapped protein were compared with different levels of Ca^"*^ present in the matrix and in solution. Results suggested that for both of the proteins, the response time and the ability to bind terbium could be adjusted by adding excess calcium to the matrix before gelation. However, the less stable protein Y57W only retained at most 45% of its binding ability in solution while the more stable protein CDOM33 was able to retain 100% binding ability. Themially induced denaturation also suggested that CDOM33 showed similar stability to the protein in solution while Y57W was destabilized. All these results suggested that "hard" proteins (i.e. very stable) can easily survive the sol-gel encapsulation process, but "soft" proteins with lower thermodynamic stability may not be able to withstand the sol-gel process. However, it is possible to control many parameters in order to successfully entrap biological molecules into the sol-gel matrices with maxunum retention of activity.

Investigations towards the synthesis of isotope labelled analogues of tocopherols and tocotrienols /

Vitamin E is considered as the most effective lipophilic chain breaking antioxidant. a-Tocopherol and its analogues have been studied thoroughly with regards to its biokinetics and bioavailabily. Deuterated tocopherols have been synthesized and utilized in such studies. Tocotrienols are arousing more and more interest because of their high efficiency as antioxidants. However, to date, there is no effective synthetic method reported for deuterated tocotrienols. This thesis is focused on the investigation of the synthetic methods of deuterated tocotrienols and their analogues: 5-trideuteromethyl-a-tocotrienol, 5- trideuteromethyl-p-tocotrienol, tocotrienol acetate, silyl tocotrienol ether, etc. Several synthetic procedures for the preparation of poly-deuterated tocopherols are known. Mainly the deuterium is introduced by use of labelled formaldehyde and deuterated hydrogen chloride under Lewis acid catalysis. However, these methods are not effective in tocotrienols due to exchange of protons for deuterium at other sites under the acidic conditions. We developed several different approaches to generate polydeuterated tocotrienols by using both morpholinomethylation followed by reduction with NaCNBDs as deuterated reducing reagents and transmetalation strategy. The 5-trideuteromethyl-a-tocotrienol was finally obtained in a satisfactory yield of 60%. In addition, this thesis also discussed the study of structural comparison and the chemical property difference of tocopherols and tocotrienols, which provides hints to explain the reactivity difference of them towards oxidation at the C3-C4 positions.Furthermore, the methodology of halogenation and dehydrohalogenation of tocotrienol was explored to prepare a hexaene tocotrienol derivative as a florescent reporter of tocopherol.

Reactivity characteristics of cytochrome c, cytochrome oxidase and the electrostatic cytochrome c - cytochrome oxidase complex /

The mechanism whereby cytochrome £ oxidase catalyses elec-. tron transfer from cytochrome £ to oxygen remains an unsolved problem. Polarographic and spectrophotometric activity measurements of purified, particulate and soluble forms of beef heart mitochondrial cytochrome c oxidase presented in this thesis confirm the following characteristics of the steady-state kinetics with respect to cytochrome £: (1) oxidation of ferrocytochrome c is first order under all conditions. -(2) The relationship between sustrate concentration and velocity is of the Michaelis-Menten type over a limited range of substrate. concentrations at high ionic strength. (3) ~he reaction rate is independent from oxygen concentration until very low levels of oxygen. (4) "Biphasic" kinetic plots of enzyme activity as a function of substrate concentration are found when the range of cytochrome c concentrations is extended; the biphasicity ~ is more apparent in low ionic strength buffer. These results imply two binding sites for cytochrome £ on the oxidase; one of high affinity and one of low affinity with Km values of 1.0 pM and 3.0 pM, respectively, under low ionic strength conditions. (5) Inhibition of the enzymic rate by azide is non-c~mpetitive with respect to cytochrome £ under all conditions indicating an internal electron transfer step, and not binding or dissociation of £ from the enzyme is rate limiting. The "tight" binding of cytochrome '£ to cytochrome c oxidase is confirmed in column chromatographic experiments. The complex has a cytochrome £:oxidase ratio of 1.0 and is dissociated in media of high ionic strength. Stopped-flow spectrophotometric studies of the reduction of equimolar mixtures and complexes of cytochrome c and the oxidase were initiated in an attempt to assess the functional relevance of such a complex. Two alternative routes -for reduction of the oxidase, under conditions where the predominant species is the £ - aa3 complex, are postulated; (i) electron transfer via tightly bound cytochrome £, (ii) electron transfer via a small population of free cytochrome c interacting at the "loose" binding site implied from kinetic studies. It is impossible to conclude, based on the results obtained, which path is responsible for the reduction of cytochrome a. The rate of reduction by various reductants of free cytochrome £ in high and low ionic strength and of cytochrome £ electrostatically bound to cytochrome oxidase was investigated. Ascorbate, a negatively charged reagent, reduces free cytochrome £ with a rate constant dependent on ionic strength, whereas neutral reagents TMPD and DAD were relatively unaffected by ionic strength in their reduction of cytochrome c. The zwitterion cysteine behaved similarly to uncharged reductants DAD and TI~PD in exhibiting only a marginal response to ionic strength. Ascorbate reduces bound cytochrome £ only slowly, but DAD and TMPD reduce bound cytochrome £ rapidly. Reduction of cytochrome £ by DAD and TMPD in the £ - aa3 complex was enhanced lO-fold over DAD reduction of free £ and 4-fold over TMPD reduction of free c. Thus, the importance of ionic strength on the reactivity of cytochrome £ was observed with the general conclusion being that on the cytochrome £ molecule areas for anion (ie. phosphate) binding, ascorbate reduction and complexation to the oxidase overlap. The increased reducibility for bound cytochrome £ by reductants DAD and TMPD supports a suggested conformational change of electrostatically bound c compare.d to free .£. In addition, analysis of electron distribution between cytochromes £ and a in the complex suggest that the midpotential of cytochrome ~ changes with the redox state of the oxidase. Such evidence supports models of the oxidase which suggest interactions within the enzyme (or c - enzyme complex) result in altered midpoint potentials of the redox centers.

Electrogenic proton/L-glutamate symport in isolated asparagus sprengeri mesophyll cell

Medium' alkaliniiation occurred -lipon the addition of L-Glu to mechanically isolated Asparagus sprenger-i mesophyll cells suspended in 1 mM CaS04. Alkalinization resulted from the coupled entry of H+ and L-Glu anion into the cells. This H+ IL-Glu symport did not stimulate K+ efflux. K+ efflux has been observed during H~ lamino acid symport in other systems. The stimulation of K+ efflux by proton coupled symport is regarded as an indicator of a plasma membrane depolarizing electrogenic symport process. H+ IL-Glu symport in Asparagus sprengerimesophyl1 cells was investigated to determine whether or not the process was electrogenic. The rate of uptake of 0.25 11M 3H-MTPP+ ( Methyltriphenylphosphonium, methyl-3H ) is a probe for monitoring changes in the membrane potential. 3HMTPP+ uptake was reduced by K+ or CCCP, agents known to depolarize the membrane potential. Uptake of 3H-MTPP+ was also inhibited by L-Glu but not by D-Glu. Conversely, 10 mM external MTPP+ inhibited the uptake of 14C-U-LGlu. Simultaneous measurements of the rates of 14C-U-L-Glu uptake and L-Glu dependent H+ influx showed that the molar stoichiometry of H+ IL-Glu symport was 2 to 1. K+ or Na+ stimulated H+ efflux was completely inhibited by DCCD, DES, oligomycin and antimycin reagents which inhibit ATP driven H+ efflux. The H+ efflux \Vas also stimulate.d by the weak acids, butyric acid and acetic acid, which are known fo-aCidify the cytoplasm. This weak acid stimulated H+ efflux was also completely inhibited by oligomycin. It was calculated that net L-Glu dependent H+ influx increased by 100% in the presence of oligomycin and that despite net medium alkalinization H+ IL-Glu symport stimulates ATP dependent H+ efflux. 11 The data presented in this study indicate that H+ IL-Glu symport is electrogenic. The data also show that ATP dependent Ht efflux rather than K+ efflux is the- process compensating for thi~ electrogenic H+ IL-Glu symport.

The application of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates in biological samples /|nby David J. LeBlanc. -- 260 St. Catharines [Ont. : s. n.],

A study was undertaken' to determine the applicability of gas liquid chromatography to the simultaneous analysis of sugars and sugar phosphates from biological samples. A new method of silylation involving dimethylsulfoxide, hexamethyldisilazane, trimethylchlorosilane and cyclohexane (1:0.2:0.1:1) which rapidly silylated sugars and sugar phosphates was developed. Subsequent chromatography on a 5% SE-52 column gave good resolution of the sugar and sugar phosphate samples. Sugar phosphates decomposed during chromatography and were lost at the 7 x 10-3 ~mole level. Acidic ethanol extraction of yeast samples revealed background contamination from the yeast sample, the culture medium and the silylation reagents which would further limit the level of detection obtainable with the glc for sugars in biological samples to the 3 x 10-4 ~mole level.

The crystal and molecular structure of thiamine hydroiodide /|nWilliam Edward Lee. -- 260 St. Catharines [Ont.] : Dept. of Chemistry, Brock University,

The x-ray crystal structure of thiamine hydroiodide,C1ZH18N40S12' has been determined. The unit cell parameters are a = 13.84 ± 0.03, o b = 7.44 ± 0.01, c = 20.24 ± 0.02 A, 8 = 120.52 ± 0.07°, space group P2/c, z = 4. A total of 1445 reflections having ,2 > 2o(F2), 26 < 40° were collected on a Picker four-circle diffractometer with MoKa radiation by the 26 scan technique. The structure was solved by the heavy atom method. The iodine and sulphur atoms were refined anisotropically; only the positional parameters were refined for the hydrogen atoms. Successive least squares cycles yielded an unweighted R factor of 0.054. The site of protonation of the pyrimidine ring is the nitrogen opposite the amino group. The overall structure conforms very closely to the structures of other related thiamine compounds. The bonding surrounding the iodine atoms is distorted tetrahedral. The iodine atoms make several contacts with surrounding atoms most of them at or near the van der Waal's distances A thiaminium tetrachlorocobaltate salt was produced whose molecular and crystal structure was j~dged to be isomorphous to thiaminium tetrachlorocadmate.

The versatility and utilization of phosphorus based compounds in classic carbon-carbon bond forming and esterification reactions

The phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) has been employed as an efficient reusable media for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts ofwater and toluene (single phase) using potassium phosphate and 1% Pd2(dba)3'CHCI3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and were all complete within 1 hour at 50°C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70°C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system, from which the catalyst was then recycled by removing the top (hexanes) and bottom (aqueous) layers and adding the reagents to the ionic liquid which was heated again at 50°C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences. IL ESTERIFICATIONREACTION A new class oftrialkylphosphorane has been prepared through reaction of a trialkylphosphine with 2-chlorodimethylmalonate in the presence oftriethylamine. These new reagents promote the condensation reaction of carboxylic acids with alcohols to provide esters along with trialkylphosphine oxide and dimethylmalonate. The condensation reaction of chiral secondary alcohols can be controlled to give either high levels of inversion or retention through a subtle interplay involving basicity of the reaction media, solvent, and tuning the electronic and steric nature of the carboxylic acid and stenc nature of the phosphorane employed. A coherent mechanism is postulated to explain these observations involving reaction via an initial acyloxyphosphonium ion.

Modifications to the Suzuki reaction and mechanistic insights on the NBS mediated cleavage of benzylidene acetals /

One of the most challenging tasks for a synthetic organic chemist today, is the development of chemo, regio, and stereoselective methodologies toward the total synthesis of macromolecules. r . The objective of my thesis was to develop methodologies towards this end. The first part of my project was to develop highly functionalized chirons from D-glucose, a cheap, chiral starting material, to be utilized in this capacity. The second part of the project dealt with modifying the carbon-carbon bond forming Suzuki reaction, which is utilized quite often as a means of combining molecular sub units in total synthesis applications. As previously stated the first area of the project was to develop high value chirons from D-glucose, but the mechanism of their formation was also investigated. The free radical initiated oxidative fragmentation of benzylidene acetals was investigated through the use of several test-case substrates in order to unravel the possible mechanistic pathways. This was performed by reacting the different acetals with N-bromosuccinimide and benzoyl peroxide in chlorobenzene at 70^C in all cases. Of the three mechanistic pathways discussed in the literature, it was determined, from the various reaction products obtained, that the fragmentation of the initial benzylic radical does not occur spontaneously but rather, oxidation proceeds to give the benzyl bromide, which then fragments via a polar pathway. It was also discovered that the regioselectivity of the fragmentation step could be altered through incorporation of an allylic system into the benzylidene acetal. This allows for the acquisition of a new set of densely functionalized. chiral, valuable synthetic intermediates in only a few steps and in high yields from a-Dglucose. The second part of the project was the utilization of the phosphonium salt room temperature ionic liquid tetradecyltrihexylphosphonium chloride (THPC) as an efficient reusable medium for the palladium catalyzed Suzuki cross-coupling reaction of aryl halides, including aryl chlorides, under mild conditions. The cross-coupling reactions were found to proceed in THPC containing small amounts of water and toluene using potassium phosphate and 1% Pd2(dba)3. Variously substituted iodobenzenes, including electron rich derivatives, reacted efficiently in THPC with a variety of arylboronic acids and afforded complete conversion within 1 hour at 50 ^C. The corresponding aryl bromides also reacted under these conditions with the addition of a catalytic amount of triphenylphosphine that allowed for complete conversion and high isolated yields. The reactions involving aryl chlorides were considerably slower, although the addition of triphenylphosphine and heating at 70 ^C allowed high conversion of electron deficient derivatives. Addition of water and hexane to the reaction products results in a triphasic system in which the top hexane phase contained the biaryl products, the palladium catalyst remained fully dissolved in the central THPC layer, while the inorganic salts were extracted into the lower aqueous phase. The catalyst was then recycled by removing the top and bottom layers and adding the reagents to the ionic liquid which was heated again at 50 ^C; resulting in complete turnover of iodobenzene. Repetition of this procedure gave the biphenyl product in 82-97% yield (repeated five times) for both the initial and recycled reaction sequences.

Stereoselective synthesis of substituted hexahydro-3a,4a-diazacyclopentaphenanthren-4-ones and aminoferrocenes

This thesis explored the development of several methodologies for the stereoselective construction of ligand frameworks and some of their applications. The first segment concerns the application of an enantioselective lithiation at an Sp3_ hybridized position adjacent to nitrogen by means of the widely used and typically highly effective enantioselective lithiation with ( -)-sparteine. This investigation was intended to develop a method to install chirality into a system that would be converted into a family of diaminoylidenes for use as phosphine mimics in transition metal catalysis or as nucleophilic reagents. Molecular modeling of the system revealed some key interactions between the substrate and (-)-sparteine that provided general insight into the diamine's mode of action and should lend some predictive value to its future applications. The second portion focuses on the development of methods to access 1,2- disubstituted aminoferrocenes, an underexplored class of metallocenes possessing planar chirality. Two routes were examined involving a diastereoselective and an enantioselective pathway, where the latter method made use of the first BF3-mediated lithiation-substitution to install planar chirality. Key derivatives such as 1,2- aminophosphines, made readily accessible by the new route, were evaluated as ligands for Pd(II), Pt(II) and Ir(I). These complexes show activity in a number of transformations with both achiral and prochiral substrates. Optimization experiments were conducted to prepare enantiomerically enriched 2-substituted-I-aminoferrocenes by direct asymmetric lithiation of BF3-coordinated tertiary aminoferrocenes. A predictive computational model describing the transition state of this reaction was developed in collaboration with Professor Travis Dudding's group (Department of Chemistry, Brock University). The predicted stereochemistry of the process was confirmed by single-crystal X-ray analysis of a 2-phosphino-l-dimethylaminoferrocene derivative. Enantiomerically pure samples of the aminophosphine ligands derived from this new process have given promising preliminary results in the enantioselective hydrogenation of prochiral alkenes and warrant further stUdy in metal-mediated catalysis.

Development of thermally stable versions of the Burgess Reagent : approaches to the chemoenzymatic total synthesis of morphine

The present studies describe our recent work on expanding the use of the Burgess reagent and its reaction with oxiranes. Several new variants of the Burgess reagent and its chiral auxiliary version were evaluated for their thermal stability by NMR spectroscopy. Three new versions of the reagent were synthesized and their stability was determined. The reactivity of all five Burgess reagents was compared in a dehydration reaction and reactions with epoxides and diols. Progress toward a chemoenzymatic synthesis of morphine is also included in this report. The synthesis began with the whole cell oxidation of bromobenzene by Escherichia coli JMI09(pDTG601). The preparation of several precursors for a key step involving the lohnson-Claisen rearrangement and progress toward the total synthesis are described.

Tetrathiafulvalene and 2,2'-Bipyridine: Bridging both Worlds in the Pursuit of Novel Molecular Materials

The preparation and characterization of two families of building blocks for molecule-based magnetic and conducting materials are described in three projects. In the first project the synthesis and characterization of three bis-imine ligands LI - L3 is reported. Coordination of LI to a series of metal salts afforded the five novel coordination complexes Sn(L4)C4 (I), [Mn(L4)(u-CI)(CI)(EtOH)h (II), [CU(L4)(u-sal) h(CI04)2 (sal = salicylaldehyde anion) (III), [Fe(Ls)2]CI (IV) and [Fe(LI)h(u-O) (V). All complexes have been structurally and magnetically characterized. X-ray diffraction studies revealed that, upon coordination to Lewis acidic metal salts, the imine bonds of LI are susceptible to nucleophilic attack. As a consequence, the coordination complexes (I) - (IV) contain either the cyclised ligand L4 or hydrolysed ligand Ls. In contrast, the dimeric Fe3+ complex (V) comprises two intact ligand LI molecules. In. this complex, the ligand chelates two Fe(III) centres in a bis-bidentate manner through the lone pairs of a phenoxy oxygen and an imine nitrogen atom. Magnetic studies of complexes (II-V) indicate that the dominant interactions between neighbouring metal centres in all of the complexes are antiferromagnetic. In the second project the synthesis and characterization two families of TTF donors, namely the cyano aryl compounds (VI) - (XI) and the his-aryl TTF derivatives (XII) - (XIV) are reported. The crystal structures of compounds (VI), (VII), (IX) and (XII) exhibit regular stacks comprising of neutral donors. The UV -Vis spectra of compounds (VI) - (XIV) present an leT band, indicative of the transfer of electron density from the TTF donors to the aryl acceptor molecules. Chemical oxidation of donors (VI), (VII), (IX) and (XII) with iodine afforded a series of CT salts that where possible have been characterized by single crystal X -ray diffraction. Structural studies showed that the radical cations in these salts are organized in stacks comprising of dimers of oxidized TTF donors. All four salts behave as semiconductors, displaying room temperature conductivities ranging from 1.852 x 10-7 to 9.620 X 10-3 Scm-I. A second series of CT salts were successfully prepared via the technique of electrocrystallization. Following this methodology, single crystals of two CT salts were obtained. The single crystal X-ray structures of both salts are isostructural, displaying stacks formed by trimers of oxidized donors. Variable temperature conductivity measurements carried out on this series of CT salts reveal they also are semiconductors with conductivities ranging from 2.94 x 10-7 to 1.960 X 10-3 S em-I at room temperature. In the third project the synthesis and characterization of a series of MII(hfac)2 coordination complexes of donor ligand (XII) where M2+ = Co2+, Cu2+, Ni2+ and Zn2+ are reported. These complexes crystallize in a head-to-tail arrangement of TTF donor and bipyridine moieties, placing the metal centres and hfac ligands are located outside the stacks. Magnetic studies of the complexes (XV) - (XVIII) indicate that the bulky hfac ligands prevent neighbouring metal centres from assembling in close proximity, and thus they are magnetically isolated.

A DFT Guided/Experimental Approach to Asymmetric Allylation and Phase-Transfer Catalysis

The Dudding group is interested in the application of Density Functional Theory (DFT) in developing asymmetric methodologies, and thus the focus of this dissertation will be on the integration of these approaches. Several interrelated subsets of computer aided design and implementation in catalysis have been addressed during the course of these studies. The first of the aims rested upon the advancement of methodologies for the synthesis of biological active C(1)-chiral 3-methylene-indan-1-ols, which in practice lead to the use of a sequential asymmetric Yamamoto-Sakurai-Hosomi allylation/Mizoroki Heck reaction sequence. An important aspect of this work was the utilization of ortho-substituted arylaldehyde reagents which are known to be a problematic class of substrates for existing asymmetric allylation approaches. The second phase of my research program lead to the further development of asymmetric allylation methods using o-arylaldehyde substrates for synthesis of chiral C(3)-substituted phthalides. Apart from the de novo design of these chemistries in silico, which notably utilized water-tolerant, inexpensive, and relatively environmental benign indium metal, this work represented the first computational study of a stereoselective indium-mediated process. Following from these discoveries was the advent of a related, yet catalytic, Ag(I)-catalyzed approach for preparing C(3)-substituted phthalides that from a practical standpoint was complementary in many ways. Not only did this new methodology build upon my earlier work with the integrated (experimental/computational) use of the Ag(I)-catalyzed asymmetric methods in synthesis, it provided fundamental insight arrived at through DFT calculations, regarding the Yamamoto-Sakurai-Hosomi allylation. The development of ligands for unprecedented asymmetric Lewis base catalysis, especially asymmetric allylations using silver and indium metals, followed as a natural extension from these earlier discoveries. To this end, forthcoming as well was the advancement of a family of disubstituted (N-cyclopropenium guanidine/N-imidazoliumyl substituted cyclopropenylimine) nitrogen adducts that has provided fundamental insight into chemical bonding and offered an unprecedented class of phase transfer catalysts (PTC) having far-reaching potential. Salient features of these disubstituted nitrogen species is unprecedented finding of a cyclopropenium based C-H•••πaryl interaction, as well, the presence of a highly dissociated anion projected them to serve as a catalyst promoting fluorination reactions. Attracted by the timely development of these disubstituted nitrogen adducts my last studies as a PhD scholar has addressed the utility of one of the synthesized disubstituted nitrogen adducts as a valuable catalyst for benzylation of the Schiff base N-diphenyl methylene glycine ethyl ester. Additionally, the catalyst was applied for benzylic fluorination, emerging from this exploration was successful fluorination of benzyl bromide and its derivatives in high yields. A notable feature of this protocol is column-free purification of the product and recovery of the catalyst to use in a further reaction sequence.

Towards reverse engineering of Photosystem II: Synergistic Computational and Experimental Approaches

ABSTRACT Photosystem II (PSII) of oxygenic photosynthesis has the unique ability to photochemically oxidize water, extracting electrons from water to result in the evolution of oxygen gas while depositing these electrons to the rest of the photosynthetic machinery which in turn reduces CO2 to carbohydrate molecules acting as fuel for the cell. Unfortunately, native PSII is unstable and not suitable to be used in industrial applications. Consequently, there is a need to reverse-engineer the water oxidation photochemical reactions of PSII using solution-stable proteins. But what does it take to reverse-engineer PSII’s reactions? PSII has the pigment with the highest oxidation potential in nature known as P680. The high oxidation of P680 is in fact the driving force for water oxidation. P680 is made up of a chlorophyll a dimer embedded inside the relatively hydrophobic transmembrane environment of PSII. In this thesis, the electrostatic factors contributing to the high oxidation potential of P680 are described. PSII oxidizes water in a specialized metal cluster known as the Oxygen Evolving Complex (OEC). The pathways that water can take to enter the relatively hydrophobic region of PSII are described as well. A previous attempt to reverse engineer PSII’s reactions using the protein scaffold of E. coli’s Bacterioferritin (BFR) existed. The oxidation potential of the pigment used for the BFR ‘reaction centre’ was measured and the protein effects calculated in a similar fashion to how P680 potentials were calculated in PSII. The BFR-RC’s pigment oxidation potential was found to be 0.57 V, too low to oxidize water or tyrosine like PSII. We suggest that the observed tyrosine oxidation in BRF-RC could be driven by the ZnCe6 di-cation. In order to increase the efficiency of iii tyrosine oxidation, and ultimately oxidize water, the first potential of ZnCe6 would have to attain a value in excess of 0.8 V. The results were used to develop a second generation of BFR-RC using a high oxidation pigment. The hypervalent phosphorous porphyrin forms a radical pair that can be observed using Transient Electron Paramagnetic Resonance (TR-EPR). Finally, the results from this thesis are discussed in light of the development of solar fuel producing systems.