Supramolecular chemistry is the study of discreet molecules assembled into more complex structures though non-covalent interactions such as host-guest effects, pi-pi stacking, electrostatic effects, hydrogen bonding, and metal-ligand interactions. Using these interactions, complex hierarchical assembles can be created from relatively simple precursors. Of the supramolecular interactions listed above, metal-ligand interactions are of particular interest due to the wide possible properties which they present. Factors such as the denticity, polarizability, steric hindrance, ligand structure, and the metal used (among others) contribute to a dramatic range in the physical properties of the metal-ligand complexes. Particularly affected by these factors are the kinetic and thermodynamic properties of the complexes. As a result metal-ligand interactions can vary from inert to extremely transient. Of the vast number of ligands available for study, this dissertation will center on substituted terpyridine ligands, with a particular focus on terpyridine-functionalized polymers. While polymer-functionalized terpyridine ligands and their complexes with transition metals have been heavily studied, the physical properties, particularly the effects of polymer functionalization on the stability of bis complexes of terpyridines, remain unexplored. In the course of investigating the kinetic stability of these complexes, polymer functionalization techniques were developed which were found to increase the stability of the metal-ligand interactions compared to conventional techniques. In addition to studying the effect of terpyridine substituents, the effects of solvent on the stability of the complexes was studied as well. As polymer-bound terpyridine complexes are often studied in solvents other than water, knowledge of the stability of the complexes in organic solvents is important to create supramolecular structures with more precisely controlled properties. It was found that, for unsubstituted terpyridyl complexes, the stability of the complexes varied by as many as five orders of magnitude in common solvents. It is believed that this decrease in stability is the result of the ability of the solvent to facilitate the movement of the ligands from the first and second coordination spheres. Although a large part of this dissertation is dedicated to the study of the kinetic stability of terpyridine complexes, synthetic techniques involving terpyridine and its complexes were investigated as well. It was found that terpyridine functionalized polystyrene could be produced by direction functionalization of terpyridine with polystyryllithium. Additionally heterloleptic terpyridine-based iron complexes were produced with high purity by reduction of the mono terpyridine complex of iron(III) in the presence of a second, functionalized terpyridine ligand. The culmination of these studies was the synthesis of supramolecular organogels, which were crosslinked using metal-terpyridine complexes, yielding dynamic mechanical properties could be broadly tuned by varying the metal used to form the crosslinks.

A variety of new chiral one-carbon-bridged metallocene derivatives of titanium and zirconium have been prepared. Addition of the anions of cyclopentadiene, indene and fluorene to 6-t-butylfulvene and 6,6-dimethylfulvene produced the ligands t-BuCH(C$\sb5$H$\sb5$)R (R = C$\sb5$H$\sb5$, 22; C$\sb9$H$\sb7$, 23; C$\sb{13}$H$\sb9$, 26) and (CH$\sb3$)$\sb2$C(C$\sb5$H$\sb5$)R (R = C$\sb9$H$\sb7$, 24; 3-CH$\sb3$-C$\sb9$H$\sb6$, 25). The reaction of the ligands 22-26 with n-BuLi produced the corresponding bis-anions, which were reacted with titanium or zirconium tetrachloride at low temperature ($-$78$\sp\circ$C), to produce the complexes t-BuCH($\eta\sp5$-C$\sb5$H$\sb4$)(R)MCl$\sb2$ (R = $\eta\sp5$-C$\sb5$H$\sb4$, M = Ti, 27; R = $\eta\sp5$-C$\sb5$H$\sb4$, M = Zr, 29; R = $\eta\sp5$-C$\sb9$H$\sb6$, M = Ti, 30; R = $\eta\sp5$-C$\sb9$H$\sb6$, M = Zr, 31; R = $\eta\sp5$-C$\sb{13}$H$\sb8$, M = Zr, 32) and (CH$\sb3$)$\sb2$C($\eta\sp5$-C$\sb5$H$\sb4$)(R)MCl$\sb2$ (R = $\eta\sp5$-C$\sb9$H$\sb6$, M = Ti, 34; R = $\eta\sp5$-C$\sb9$H$\sb6$, M = Zr, 14; R = 3-CH$\sb3$-$\eta\sp5$-C$\sb9$H$\sb5$, M = Ti, 35; R = 3-CH$\sb3$-$\eta\sp5$-C$\sb9$H$\sb5$, M = Zr, 36). The structure of 34 is very rigid due to strain at the bridgehead carbon. The chlorine atoms in complexes 27 and 32 can be easily replaced by methyl groups. By treatment of 27 and 32 with MeLi in diethyl ether the corresponding dimethyl derivatives 28 and 33 were obtained. The influence of the symmetry of the bridge in metallocene Ziegler-Natta catalysis was tested. The chiral complex 32 was compared to the symmetric system $\rm (CH\sb3)\sb2C(\eta\sp5$-$\rm C\sb5H\sb4)(\eta\sp5$-$\rm C\sb{13}H\sb8)ZrCl\sb2({\bf 52})$ in the syndiospecific polymerization of propylene. The polymerization behavior of precursors 32 and 52 were very similar. The substituents on the bridgehead carbon had little or no influence on the polymerization process because of their remote location from the available coordination sites involved in the polymerization reaction. The symmetry of the cyclopentadienyl groups was also tested for the polymerization of propylene with metallocene systems. Precursors 14 and 36 polymerized propylene to low molecular weight materials in reduced activities compared to the symmetric precursor 52. The polymers obtained with 14 and 36 present a structure assigned to hemiisotactic chains. New sulfur and selenium derivatives of the mixed sandwich complex ($\eta\sp5$-$\rm C\sb5H\sb5)(\eta\sp7$-$\rm C\sb7H\sb7)Ti\ ({\bf 63})$ were prepared. Complexes ($\eta\sp5$-$\rm C\sb5H\sb5)(\eta\sp7$-$\rm C\sb7H\sb6$R)Ti (R = SCH$\sb3$, 82; SPh, 84; SePh, 86), ($\eta\sp5$-$\rm C\sb5H\sb4R)(\eta\sp7$-$\rm C\sb7H\sb7$)Ti (R = SCH$\sb3$, 81) and ($\eta\sp5$-$\rm C\sb5H\sb4R)(\eta\sp7$-$\rm C\sb7H\sb6$R)Ti (R = SCH$\sb3$, 80; SPh, 83; SePh, 85) were prepared by reaction of the mono- or dilithio-derivatives of 63 with one or two equivalents of the corresponding dichalcogenide. Compound 80 behaved as a bidentated ligand. Heterobimetallic derivatives 88-90 were obtained by treatment of 80 with Cr(CO)$\sb4$(nbd), Cr(CO)$\sb4$(nbd) and PtCl$\sb2$(PhCN)$\sb2$, respectively.

This thesis reports on the synthesis of a series of Lewis acidic boranes used as detectors for the cyanide or fluoride ion, and for the activation of molecular oxygen. Chapter III focuses on the formation of monodentate boranes featuring a pendant ferrocenyl moiety. A systematic study of the fluoride and cyanide binding capabilities of isomeric ferrocenyl-functionalized phenyl boranes was conducted via spectroscopic, crystallographic and voltammetric techniques. The synthesis of receptors supported by an indenyl scaffold was also investigated and the binding properties of such systems studied in details. All receptors proved to be competent at binding both cyanide and fluoride in dry solvents; moreover one such indenyl receptor can selectively bind cyanide in aqueous media and signal the binding event by a green-to-red colour change. Chapter IV constitutes an extension of the previous chapter targeting bidentate receptors with an (indenyl)(cyclopentadienyl)iron(II) back bone. A principle objective was the development of systems offering the chelation of fluoride, and hence a measure of selectivity over the more strongly basic cyanide ion. While bis(dimesitylborane) receptors proved to be synthetically inaccessible, a series of phosphine- and phosphonium-borane species was prepared and their comparative F-/CN- binding abilities determined. Thus, while cationic phosphonium boranes favour fluoride binding by employing a bifunctional binding motif, the neutral phosphine boranes exclusively bind cyanide. Chapter V details the activation of molecular oxygen by pentafluorophenyl-boranes in presence of weak reductants featuring a ferrocene unit. The highly Lewis acidic ferrocenyl bis(pentafluorophenyl)borane was initially studied, and its reaction with dry dioxygen shown to generate a (fully characterized) ferrocenium peroxoborate. Similar reactivity was observed for simple metallocenes such as cobaltocene and ferrocene (or even organic reductants) in presence of a strong Lewis acid, with the trapping of the O₂²- ion by the borane thought to be a key thermodynamic driving force for the O₂ reduction.

This Thesis describes the synthesis and characterisation of half-sandwich complexes supported by κ¹-amidinate and κ¹-guanidinate ligands as well as the cationic species produced on activation. The chemistry of the cationic species is detailed and DFT studies which have also been carried out to elucidate the bonding in relevant complexes are also presented.

This thesis explores the reactivity of amine-boranes with the {Rh(Xantphos)}+ fragment, with the aim of gaining mechanistic insight into the catalytic dehydropolymerisation of the amine-borane H₃B∙NMeH₂ to yield the polyaminoborane [H₂BNMeH]_n. Chapter 2 describes the synthesis of suitable Rh^III and Rh^I Xantphos precursors to be used in this investigation. Moreover, the first example of the dehydrogenative B—B homocoupling of the tertiary amine-borane H₃B∙NMe₃ to form H₄B₂•2NMe₃ is reported. The synthesis of the Rh^I precatalyst introduced in Chapter 2 entails the hydroboration of tert-butylethylene by H₃B∙NMe₃. In Chapter 3, the ability of the {Rh(Xantphos)}+ fragment to mediate this hydroboration in a catalytic manner is explored, and a mechanism is presented in which reductive elimination is proposed to be turnover-limiting. Other alkenes and phosphine-boranes are also trialled to determine the scope of the hydroboration. Chapter 4 investigates the catalytic dehydrocoupling of H₃B∙NMe₂H and H₃B∙NMeH₂ with {Rh(Xantphos)}+ to form the dehydrocoupling products [H₂BNMe₂]₂ and [H₂BNMeH]_n, respectively, and the dehydrocoupling mechanisms are shown to be similar. Both involve an induction period in which the active catalyst is formed (thought to involve N—H activation), and saturation kinetics operate during the productive phase of catalysis. H₂ is shown to inhibit the dehydrocoupling, and lead to production of shorter chain [H₂BNMeH]_n. Conversely, using THF as the dehydropolymerisation solvent instead of C₆H₅F results in longer chain [H₂BNMeH]_n. Finally, Chapter 5 presents new dicationic {Rh(Xantphos)}-based dimers, the formation of which involves loss of a phenyl group from the Xantphos ligands by P—C activation. The dimers are produced by routes involving either dehydrogenative homocoupling of H₃B∙NMe₃, or dehydrocoupling of H₃B∙NMe₂H. One of these dimers was tested as a catalyst for the dehydrocoupling of H₃B∙NMe₂H, and the reaction kinetics appear closely related those obtained using {Rh(Xantphos)}+, suggesting that the active catalysts in each system may be related.

<p> In this work the redox properties of cytochrome c nitrite reductase (CcNiR), a decaheme homodimer that was isolated from <i>S. oneidensis,</i> were determined in the presence and absence of the strong-field ligands cyanide and nitrite. Four hemes per CcNiR protomer are hexa-coordinate with tightly bound axial histidines, while the fifth (active site) has one tightly bound lysine and a distal site that can be open, or contain exogenous ligands such as the substrate nitrite. Controlled potential electrolysis in combination with UV/visible absorption (UV-vis) and electron paramagnetic resonance (EPR) spectroscopies allowed for assignment of all heme midpoint potentials under each set of conditions. The studies show that the active-site heme is the first to be reduced under all conditions. The midpoint redox potential of that heme shifts approximately 70mV to the positive upon binding a strong field ligand such as nitrite or cyanide. When controlled potential electrolysis was carried out in the presence of nitrite, a concerted two electron reduction was observed by UV-vis, and a {Fe(NO)}⁷ reduced product was revealed in EPR. In addition, an asymmetry in ligand binding between active sites was revealed. This information is relevant for the interpretation of planned and ongoing mechanistic studies of CcNiR. </p><p> Over-expression, partial purification and characterization of another <i> S. oneidensis</i> multiheme enzyme, known as octaheme tetrathionate reductase (OTR), is also described herein. Though of unknown cellular function, OTR was previously reported to have tetrathionate reductase activity, in addition to nitrite and hydroxylamine reductase activities. The new results indicate that the expression of OTR has no effect on tetrathionate or nitrite reductase activities in the whole cell lysate, and only hydroxylamine reductase activity was substantially elevated in the overexpressing bacteria. OTR was stable in buffered solutions, but substantial activity loss during all attempts at column chromatography was a major obstacle to the complete purification. OTR also proved quite hydrophobic, so possible membrane association should be considered in future attempts to purify this protein. </p><p> Finally, this dissertation also reports attempts to improve <i> S. oneidensis'</i> ability to express foreign proteins. Though ideally suited to expressing c-hemes, it proved difficult to express carboxy his-tagged proteins in <i>S. oneidensis</i> because of persistent tag degradation. Attempts to knock out lon protease, a cytoplasmic carboxypeptidase, as well as the result of redirecting ccNiR from the SecA to the possibly more protected signal particle recognition (SRP) secretion pathway, are described. </p><p> Iron heme cofactors are single-electron transport moieties that play a crucial role in respiration. While oxygen is the electron acceptor of choice in aerobic atmospheres, microorganisms that live in anaerobic environments utilize other molecules with similarly high reduction potentials. <i> S. oneidensis</i> can utilize numerous terminal electron acceptors, including nitrite, dimethylsulfoxide and even uranium, thanks to a particularly rich array of multi c-heme respiratory proteins. Understanding of how the midpoint potentials and heme arrangements within the proteins influence these exotic respiratory processes is of interest in the fields of bioremediation and fuel development.</p>

<p> There has been much interest in colloidal noble metal nanoparticles due to their fascinating plasmonic and catalytic properties. These properties make noble metal nanoparticles potentially useful for applications such as targeted drug delivery agents and hydrogen storage devices. Historically, shape-controlled noble metal nanoparticles have been predominantly monometallic. Recent synthetic advances provide access to bimetallic noble metal nanoparticles wherein their inherent multifunctionality and ability to fine tune or expand their surface chemistry and light scattering properties of metal nanoparticles make them popular candidates for many applications. Even so, there are currently few synthetic strategies to rationally design shape-controlled bimetallic nanocrystals; for this reason, few architectures are accessible. For example, the "seed-mediated method" is a popular means of achieving monodisperse shape-controlled bimetallic nanocrystals. In this process, small metal seeds are used as platforms for additional metal addition, allowing for conformal core@shell nanostructures. However, this method has only been applied to single metal core/single metal shell structures; therefore, the surface compositions and architectures achievable are limited. This thesis expands upon the seed-mediated method by coupling it with co-reduction. In short, two metal precursors are simultaneously reduced to deposit metal onto pre-formed seeds in hopes that the interplay between two metal species facilitates bimetallic shell nanocrystals. Au/Pd was used as a test system due to favorable reduction potentials of metal precursors and good lattice match between Au and Pd. Alloyed shelled Au@Au/Pd nanocrystals were achieved using this "seed-mediated co-reduction" approach. Symmetric eight-branched Au/Pd nanocrystals (octopods) are also prepared using this method. This thesis investigates many synthetic parameters that determine the shape outcome in Au/Pd nanocrystals during seed-mediated co-reduction. Plasmonic, catalytic, and assembly properties are also investigated in relation to nanocrystal shape and architecture. This work provides a foundation for the rational design of architecturally defined bimetallic nanostructures. </p>

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0944. Adviser: Kenneth S. Suslick. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Monolayer protected nanoparticles (NPs) include an inorganic core and a monolayer of organic ligands. The wide variety of core materials and the tunable surface monolayers make NPs promising materials for numerous applications. Concerns related to unforeseen human health and environmental impacts of NPs have also been raised. In this thesis, new analytical methods based on mass spectrometry are developed to understand the fate, transport, and biodistributions of NPs in the complex biological systems. A laser desorption/ionization mass spectrometry (LDI-MS) method has been developed to characterize the monolayers on NP surface. LDI-MS allows multiple NPs taken up by cells to be measured and quantified in a multiplexed fashion. The correlations between surface properties of NPs and cellular uptake have also been explored. LDI-MS is further coupled with inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively measure monolayer stability of gold NPs (AuNPs) and quantum dots (QDs), respectively, in live cells. This label-free approach allows correlating monolayer structure and particle size with NP stability in various cellular environments. Finally, uptake, distribution, accumulation, and excretion of NPs in higher order organisms, such as fish and plants, have been investigated to understand the environmental impact of nanomaterials. The results indicate that surface chemistry is a primary determinant. NPs with hydrophilic surfaces are substantially less toxic and present a lower degree of bioaccumulation, making these nanomaterials attractive for sustainable nanotechnology.

The reactivity of group 15 Zintl ions, E₇^3– (E = P, As), towards a number of transition and post-transition metal reagents has been studied. The synthesis and characterisation of the resulting novel cluster anions are described herein. The reactions of E₇^3– with [Cu₅(mes)₅], MPh₂ (M = Zn, Cd) and InPh₃ yielded the Cu–Cu bridged species [Cu₂(E₇)₂]^4– (E = P, As), the group 12 bridged cluster anions [M(E₇)₂]^4– (M = Zn: E = P, As; M= Cd: E = P), and the In-functionalised Zintl ions [E₇InPh<sub>2<sub>]^2–, respectively. P₇^3– and As₇^3– have been found to react with a number of metal salts, namely [M(nbe)₃][SbF₆] and MCl (M = Ag, Au), InCl₃, TlCl and MI₂ (M = Sn, Pb). These reactions formed the Ag–Ag and Au–Au bridged complexes [M₂(HP₇)₂]^2– (M = Ag, Au), the In-bridged species [In(E₇)₂]^3– (E = P, As), the Tl-derivatised Zintl ions [TlE₇]^2– (E = P, As), and the sixteen vertex cluster anions [ME₁₅]^3– (M = Sn, Pb; E = P, As). The reactivity of P₇^3– towards a series of group 8 compounds has also been studied. The reactions of P₇^3– with FeCl₂ and [Ru(PPh₃)₃Cl₂] produced [M(HP₇)₂]^2- (M = Fe, Ru). NMR studies showed that these species can be deprotonated to form [M(P₇)₂]^4– (M = Fe, Ru). These Fe and Ru complexes are isoelectronic with ferrocene. In addition, P₇^3– reacts with [Ru(COD)(η³-CH₂C(CH₃)CH₂)₂] to form [(C₄H₇)P₇Ru(COD)]^2–. Both P₇^3– and As₇^3– undergo transition metal mediated activation reactions in the presence of [Co(PEt₂Ph₂)(mes)₂], yielding [Co(η⁵-P₅){η²-HP₂(mes)}]^2– and [Co([η³-As₃){η⁴-As₄(mes)₂}]^2–, respectively.