Triarylamminium radical-cation complexes: design and magnetic properties and Base-catalyzed hydrosilylation: mechanism and substrate scope

1. Triarylamminium radical-cation complexes. The detailed study of manganese, copper and nickel metal-radical complexes with triarylamminium ligands was conducted. Stable, neutral and pseudo-octahedral coordination monometallic complexes with simple monodentate 2,2`-bipyridine ligand containing a redox-active N,N`-(4,4`-dimethoxydiphenyl-amino) substituent were synthesized and fully characterized. The one-electron oxidation process and formation of persistent radical-cation complexes was observed by cyclic voltammetry and spectroelectrochemical measurements. Evans method measurements were performed with radical-cation complexes generated by chemical one-electron oxidation with NOPF6 in acetonitrile. The experimental results indicate ferromagnetic coupling between metal and triarylamminium cation in manganese (II) complex and antiferromagnetic coupling in nickel (II) complex. This data is supported by DFT calculations which also lend weight to the  spin polarization mechanism as an operative model for magnetic exchange coupling. Neutral bimetallic complexes with a new ditopic ligand were synthesized and fully characterized, including magnetic and electrochemical studies. Chemical oxidation of these precursor complexes did not generate radical-cations, but dicationic complexes, which was confirmed by UV-vis and EPR-experiments, as well as varied temperature magnetic measurements. DFT calculations for radical-cation complexes are included. A synthetic pathway for polytopic ligand with multiple redox-active triarylamine sites was developed. The structure of the ligand is presumably suitable for -spin polarization exchange model and allows for production of polymetallic complexes having high spin ground states. 2. Base-catalyzed hydrosilylation. A simple reductive base-catalyzed hydrosilation of aldehydes and ketones was adapted to the use of the cheap, safe, and non-toxic polymethylhydrosiloxane (PMHS) instead of the common PhSiH3 and (EtO)3SiH, which present significant cost and safety concerns, respectively. The conversion of silane into pentacoordinate silicate species upon addition of a base was studied in details for the cases of phenyl silane and PMHS and is believed to be essential for the hydrosilylation process. We discovered that nucleophiles (a base or fluoride-anion) induced the rearrangement of PMHS and TMDS into light silanes: MeSiH3 and Me2SiH2, respectively. The reductive properties of PMHS under basic conditions can be attributed to the formation of methyl silane and its conversion into a silicate species. A procedure for the generation of methyl silane and its use in further efficient reductions of aldehydes and ketones has been developed. The protocol was extended to the selective reduction of esters and tertiary amides into alcohols and aldimines into amines with good isolated yields and reduction of heterocyclic compounds was attempted.

Chemical synthesis of glycosylated oligoribonucleotides for siRNA development

In this study, an efficient methodology for the preparation of carbohydrate-RNA conjugates was established, which involved the use of 3,4~diethoxy-3-cyclobutene-l,2- dione (diethyl squarate) as the linking reagent. First, a glycan moiety containing an amino group reacted with diethyl squarate to form an activated glycan, which further reacted with an amino modified oligoribonucleotide to form a glycoconjugate under slightly basic conditions. The effect of glycosylation on the stability of RNA molecules was evaluated on two glycoconjugates, monomannosyl UlO-mer and dimannosyl UlO-mer. In the synthesis of aromatic fluorescent ribosides, perbenzylated ribofuranosyl pyrene and phenanthrene were synthesized from perbenzylated ribolactone. Deprotection of benzyl-protected ribofuranosyl phenanthrene and pyrene by boron tribromide gave ribofuranosyl phenanthrene and ribopyranosyl pyrene, respectively. UV/vis and fluorescent properties of the ribosides were characterized.

An investigation of the nature and role of historicality in the thought of Dilthey and Heidegger

Introduction The question of the meaning, methods and philosophical manifestations of history is currently rife with contention. The problem that I will address in an exposition of the thought of Wilhelm Dilthey and Martin Heidegger, centers around the intersubjectivity of an historical world. Specifically, there are two interconnected issues. First, since all knowledge occurs to a person from within his or her historical age how can any person in any age make truth claims? In order to answer this concern we must understand the essence and role of history. Yet how can we come to an individual understanding ofwhat history is when the meanings that we use are themselves historically enveloped? But can we, we who are well aware of the knowledge that archaeology has dredged up from old texts or even from 'living' monuments of past ages, really neglect to notice these artifacts that exist within and enrich our world? Charges of wilful blindness would arise if any attempt were made to suggest that certain things of our world did not come down to us from the past. Thus it appears more important 2 to determine what this 'past' is and therefore how history operates than to simply derail the possibility for historical understanding. Wilhelm Dilthey, the great German historicist from the 19th century, did not question the existence of historical artifacts as from the past, but in treating knowledge as one such artifact placed the onus on knowledge to show itself as true, or meaningful, in light ofthe fact that other historical periods relied on different facts and generated different truths or meanings. The problem for him was not just determining what the role of history is, but moreover to discover how knowledge could make any claim as true knowledge. As he stated, there is a problem of "historical anarchy"!' Martin Heidegger picked up these two strands of Dilthey's thought and wanted to answer the problem of truth and meaning in order to solve the problem of historicism. This problem underscored, perhaps for the first time, that societal presuppositions about the past and present oftheir era are not immutable. Penetrating to the core of the raison d'etre of the age was an historical reflection about the past which was now conceived as separated both temporally and attitudinally from the present. But further than this, Heidegger's focus on asking the question of the meaning of Being meant that history must be ontologically explicated not merely ontically treated. Heidegger hopes to remove barriers to a genuine ontology by II 1 3 including history into an assessment ofprevious philosophical systems. He does this in order that the question of Being be more fully explicated, which necessarily for him includes the question of the Being of history. One approach to the question ofwhat history is, given the information that we get from historical knowledge, is whether such knowledge can be formalized into a science. Additionally, we can approach the question of what the essence and role of history is by revealing its underlying characteristics, that is, by focussing on historicality. Thus we will begin with an expository look at Dilthey's conception of history and historicality. We will then explore these issues first in Heidegger's Being and Time, then in the third chapter his middle and later works. Finally, we shall examine how Heidegger's conception may reflect a development in the conception of historicality over Dilthey's historicism, and what such a conception means for a contemporary historical understanding. The problem of existing in a common world which is perceived only individually has been philosophically addressed in many forms. Escaping a pure subjectivist interpretation of 'reality' has occupied Western thinkers not only in order to discover metaphysical truths, but also to provide a foundation for politics and ethics. Many thinkers accept a solipsistic view as inevitable and reject attempts at justifying truth in an intersubjective world. The problem ofhistoricality raises similar problems. We 4 -. - - - - exist in a common historical age, presumably, yet are only aware ofthe historicity of the age through our own individual thoughts. Thus the question arises, do we actually exist within a common history or do we merely individually interpret this as communal? What is the reality of history, individual or communal? Dilthey answers this question by asserting a 'reality' to the historical age thus overcoming solipsism by encasing individual human experience within the historical horizon of the age. This however does nothing to address the epistemological concern over the discoverablity of truth. Heidegger, on the other hand, rejects a metaphysical construel of history and seeks to ground history first within the ontology ofDasein, and second, within the so called "sending" of Being. Thus there can be no solipsism for Heidegger because Dasein's Being is necessarily "cohistorical", Being-with-Others, and furthermore, this historical-Being-in-the-worldwith- Others is the horizon of Being over which truth can appear. Heidegger's solution to the problem of solipsism appears to satisfy that the world is not just a subjective idealist creation and also that one need not appeal to any universal measures of truth or presumed eternal verities. Thus in elucidating Heidegger's notion of history I will also confront the issues ofDasein's Being-alongside-things as well as the Being of Dasein as Being-in-the-world so that Dasein's historicality is explicated vis-a-vis the "sending of Being" (die Schicken des S eins).

Distribution of excitation energy in photosynthesis: a study of heat loss, photo chemical activity and fluorescence emission in intact calls of cyanobacterium.

Photosynthetic state transitions were investigated in the cyanobacterium Synechococcus sp. PCC 6301 by studying fluorescence emission, heat loss, and PS I activity in intact cells brought to state 1 and state 2. 77K fluorescence emission spectra were modelled with a sum of 6 components corresponding to PBS, PS II, and PS I emissions. The modelled data showed a large decrease in PS II fluorescence accompanied with a small increase in the PS I fluorescence upon transition to state 2 for excitation wavelengths absorbed by both PBS and ChI ll.. The fluorescence changes seen with ChI .a. excitations do not support the predictions of the mobile PBS model of state transition in PBS-containing organisms. Measurements of heat loss from intact cells in the two states were similar for both ChI it. and PBS excitations over three orders of magnitude of laser flash intensity. This suggests that the PBS does not become decoupled from PS II in state 2 as proposed by the PBS detachment model of state transition in PBS-containing organisms. PS I activity measurements done on intact cells showed no difference in the two states, in contrast with the predictions of all of the existing models of state transitions. Based on these results a model for state transition In PBScontaining organisms is proposed, with a PS II photoprotectory function.

Collective violence : a study of the gendered and socio-economic factors behind early modern Italian and English witch hunts

In this study, I build upon my previous research in which I focus on religious doctrine as a gendered disciplinary apparatus, and examine the witch trials in early modem England and Italy in light of socio-economic issues relating to gender and class. This project examines the witch hunts/trials and early modem visual representations of witches, and what I suggest is an attempt to create docile bodies out of members of society who are deemed unruly, problematic and otherwise 'undesirable'; it is the witch's body that is deemed counternormative. This study demonstrates that it is neighbours and other acquaintances of accused witches that take on the role of the invisible guard of Bantham's Panoptic on. As someone who is trained in the study of English literature and literary theory, my approach is one that is informed by this methodology. It is my specialization in early modem British literature that first exposed me to witch-hunting manuals and tales of the supernatural, and it is for this reason that my research commences with a study of representations of witches and witchcraft in early modem England. From my initial exposure to such materials I proceed to examine the similarities and the differences of the cultural significance of the supernatural vis-a.-vis women's activities in early modem Italy. The subsequent discussion of visual representations of witches involves a predominance of Germanic artists, as the seminal work on the discernment of witches and the application of punishment known as the Malleus Meleficarum, was written in Germany circa 1486. Textual accounts of witch trials such as: "A Pitiless Mother (1616)," "The Wonderful Discovery of the Witchcrafts of Margaret and Philippa Flower (1619)," "Magic and Poison: The Trial ofChiaretta and Fedele (circa 1550)", and the "The Case of Benvegnuda Pincinella: Medicine Woman or Witch (1518),"and witchhunting manuals such as the Malleus Melejicarum and Strix will be put in direct dialogue with visual representations of witches in light of historical discourses pertaining to gender performance and gendered expectations. Issues relating to class will be examined as they pertain to the material conditions of presumed witches. The dominant group in any temporal or geographic location possesses the tools of representation. Therefore, it is not surprising that the physical characteristics, sexual habits and social material conditions that are attributed to suspected witches are attributes that can be deemed deviant by the ruling class. The research will juxtapose the social material conditions of suspected witches with the guilt, anxiety, and projection of fear that the dominant groups experienced in light of the changing economic landscape of the Renaissance. The shift from feudalism to primitive accumulation, and capitalism saw a rise in people living in poverty and therefore an increased dependence upon the good will of others. I will discuss the social material conditions of accused witches as informed by what Robyn Wiegman terms a "minoritizing discourse" (210). People of higher economic standing often blamed their social, medical, and/or economic difficulties on the less fortunate, resulting in accusations of witchcraft.

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.

Novel Magnetic Materials Based on Macrocyclic Ligands: Towards High Relaxivity Contrast Agents and Mononuclear Single-Molecule Magnets

The preparation and characterization of coordination complexes of Schiff-base and crown ether macrocycles is presented, for application as contrast agents for magnetic resonance imaging, Project 1; and single-molecule magnets (SMMs), Projects 2 and 3. In Project 1, a family of eight Mn(II) and Gd(III) complexes of N3X2 (X = NH, O) and N3O3 Schiff-base macrocycles were synthesized, characterized, and evaluated as potential contrast agents for MRI. In vitro and in vivo (rodent) studies indicate that the studied complexes display efficient contrast behaviour, negligible toxicity, and rapid excretion. In Project 2, DyIII complexes of Schiff-base macrocycles were prepared with a view to developing a new family of mononuclear Ln-SMMs with pseudo-D5h geometries. Each complex displayed slow relaxation of magnetization, with magnetically-derived energy barriers in the range Ueff = 4 – 24 K. In Project 3, coordination complexes of selected later lanthanides with various crown ether ligands were synthesized. Two families of complexes were structurally and magnetically analyzed: ‘axial’ or sandwich-type complexes based on 12-crown-4 and 15-crown-5; and ‘equatorial’ complexes based on 18-crown-6. Magnetic data are supported by ab initio calculations and luminescence measurements. Significantly, the first mononuclear Ln-SMM prepared from a crown ether ligand is described.