published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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The mono protection of 1,4,7-triazacyclononane ([9]-aneN₃) was accomplished efficiently through the formation of an orthoamide derivative. The orthoamide was used to form three mono protected derivatives of [9]-aneN₃ which contained either a formyl, methyl, or benzyl protecting group attached to one of the nitrogen donors. The macrobicyclic complexes bicycloN₅, Me-bicycloN₅, and Bz-bicycloN₅ were synthesized through the Michael addition of two functional arms to the mono protected derivatives of [9]-aneN₃ followed by a ring closure template reaction around copper with glyoxal. Incomplete reduction by BH₃ THF led to the isolation of an enamine intermediate. The solution behavior o f the Ni(II) and Ni(III) complexes of these macrobicyclic ligands is presented. The methyl and benzyl derivatives were found to have similar abilities as the parent bicycloN₅ ligand to stabilize the Ni(III) metal ion. Removal of the benzyl protecting group was achieved by reaction with formic acid in the presence of a Pd/C catalyst. Attempts to couple two mono protected nonane molecules through the addition of functional acid chloride arms under conditions of high dilution were unsuccessful. Reaction of the benzyl protected bicyclic ligand Bz-bicycloN₅ with a bridging ligand in a high dilution reaction did provide evidence for the formation of a small amount of the novel macrotricyclic ligand tricyclo[9.14.9]N₆. The Ni(II) complexes of the macrobicyclic ligands, and a series of other macrocyclic and related Ni(II) complexes having varying NiIII/II redox potentials, were used to study the quenching of the excited state of the platinum(II) dimeric complex Pt₂(pop)₄⁴− . The quenching rate constants kq were determined, and quenching of the excited state *Pt₂(pop)₄⁴− by the nickel complexes was found to proceed by reductive electron transfer. These results are discussed in terms of Marcus Theory. A plot of logkq versus the ΔG for electron transfer was found to exhibit classic Rehm- Weller behavior. The excited state potential Pt₂(pop)₄⁴⁻*/⁵- was estimated from this series of quenching reactions and a range of 1.24 to 1.34 V (vs. NHE) was identified. The photochemical and photophysical properties of the macrocyclic complex Cr([18]-aneN₆)³+ ([18]-aneN₆ = 1,4,7,10,13,16-hexaazacyclooctadecane) were investigated and compared to the properties of the photoreactive Cr(III) complex Cr(sen)³+ (sen = 4,4',4"-ethylidynetris(3-azabutan-l-amine)). The complex Cr([18]- aneN₆)³+ was found to be unreactive (Ørxn < 10⁻³) while the photoreactivity of Cr(sen)³+ was confirmed (Ørxn = 0.10). Both of these complexes have very short ambient ²E emission lifetimes and this is discussed in terms of distortions imposed on the complexes by the coordination of the ligands. Direct irradiation into the doublet excited state of Cr(sen)3⁺ at 675 nm resulted in a decrease in the quantum yield for the photoreaction of this complex from Ørxn=0.10 for quartet irradiation to Ørxn=0.08 for doublet irradiation. A model is suggested in which there are two competitive processes deactivating the doublet excited state; reverse intersystem crossing to the lowest quartet excited state and nonradiative decay back to the ground state. The temperature dependence of the ²E emission lifetime was fitted to a two-term Arrhenius function to give estimates for the pre-exponential factors and activation energies of these two deactivation processes. Values of A₁ = (1.2 ± 0.9) x 1O¹⁵ s⁻¹ and Eₐ₁ = 45 ± 1 kJ mol⁻¹,and A₂ = (5.4 ± 1.2) x 10¹¹s⁻¹ and Eₐ2 = 29 ± 1 kJ mol⁻¹ were obtained. The photostereochemistry of Cr(sen)³⁺ was investigated using a modified reversed phase HPLC technique. A total of four photoproducts were identified from the photolysis of the resolved stereoisomers of Cr(sen)³⁺ and a loss of optical activity was found to be associated with the photoreaction. These results are discussed in terms of current models for predicting photostereoreactivity of Cr(III) complexes. / Graduate

Di-2-pyridinylmethanone (di-2-pyridyl ketone) is a well-known ligand within the family of basic building blocks for the construction of metal-organic complexes with diverse architectures and potential applications in relation to their physical and chemical properties. A systematic investigation on the generation and structure of transition metal complexes based on six ligands containing the dipyridinylmethanone moiety is reported in this thesis. Although all these ligands are known except L7, their coordination chemistry remains unexplored to date. / Ligand 2-pyridinyl-3-pyridinylmethanone (L1) is an excellent building block for the construction of infinite single-strand helical architectures with various metal salts. In the resultant helical complexes, Ll exhibits three kinds of coordination modes involving two kinds of bridging conformations, resulting in four types of single-strand helical chains. Among them is a pair of helical conformational polymorphs generated by the solvent-controlled process, in which the 21 helices of opposite chirality in one are stacked alternately to form a racemate, whereas the 41 helices in the other are assembled homochirally by inter-chain argentophilic interaction to generate a conglomerate. In a series of six isostructural 21 helical Ag(I) complexes, the pitch length corresponds not only to the size of the embedded anion but also to the manner of its fitting into the groove of the helix. In the Co(II) and Zn(II) complexes that comprise helical chains without anion embedment, the pitch lengths are dictated by the size of the metal cations. / Ligand 2-pyridinyl-4-pyridinylmethanone (L2) readily gives rise to dimeric metallacyclophanes with various Ag(I) salts, which bear close structural similarity. An ordered sequence of the coordinating ability of a series of nine polyatomic monoanions has been established on the basis of structural parameters derived from their interaction with a common disilver(I) metallacyclophane skeleton in isostructural complexes. The reactions of L2 with Co(II), Cu(II), Zn(II) and Cd(II) salts give rise to supramolecular architectures assembled through weak interactions including hydrogen bonding and pi&middot;&middot;&middot;pi stacking, in which L2 adopts various ligation modes. / Metal complexes of 3-pyridinyl-4-pyridinylmethanone (L4) exhibit a variety of structural types: single chain, ladder-like chain, (4,4) network and tetrameric unit. (Abstract shortened by UMI.) / Chen Xudong. / "July 2005." / Adviser: Thomas C. W. Mak. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3787. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 143-164). / 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. / Abstract in English and Chinese. / School code: 1307.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

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Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 242-243) Also available in print.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.