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Rigid Aromatic Oligoamide Scaffold-based Molecular Recognitions and a Class of [60] Fullerene Radical Reactions

Author: LiChangZhi
Tutor: WangQuanRui;LiZhanTing
School: Fudan University
Course: Organic Chemistry
Keywords: Supramolecular chemistry Foldamers Non-Covalent Interaction [60]fullerene Porphyin Molecular Recognition Self-Assembly Chirality Induction
CLC: O643.1
Type: PhD thesis
Year: 2007
Downloads: 115
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Abstract


With an increasing number of folding and helical structures available, chemists have begun to pay more attention to the functions of this family of structurally unique oligomers. Hydrogen bonding-mediated aromatic oligoamide foldamers have the features of good structural predictability, synthetic facility and structural modification, which make them very promising as scaffolds or platforms for supramolecular chemistry. One of the challenges addressed in this area is the construction of functionalized scaffolds and their further applications in molecular recognition as well as self-assembly. This dissertation focuses on hydrogen bonded aromatic oligoamides and consists five parts.In the first part, two linear compounds, 1 and 2, have been designed and synthesized as new receptors for zinc porphyrins. Both compounds consist of two folded aromatic amide moieties which are connected with an acetylene linker for 1 or directly for 2. The rigid conformations of their folded moieties are stabilized by intramolecular tri-centered hydrogen bonding, while the whole molecules adopt an "S"- or "C"-styled conformation depending on the relative orientation of the two rigid moieties. Two pyridine units are introduced at the ends of 1 and 2 for the complexation of zinc porphyrin guests. Although the 1H NMR investigation indicated that both compounds can bind two zinc porphyrin guests at high concentrations (≥5 mM) in chloroform, the UV-Vis studies revealed that, at low concentration of 1 and 2 (4μM), both compounds complex one zinc porphyrin guest to form structurally unique "two-point"-bounded 1:1 complexes. The association constants of the 1:1 complexes have been determined with the UV-vis titration experiments.In the second part, the complexing behaviour of two linear compounds 1 and 2 toward the trifluoroacetic acid (TFA) salt of n-dodecyl amine, n-dioctylamine, n-dodecyl D- and L-phenylalaninate in chloroform has been described. 1H NMR, UV-vis, fluorescent and circular dichroism investigations revealed that 1 and 2 could bind primary and secondary ammonium with their "C"-styled conformation. In the presence of 1 equiv of TFA, the binding stability was increased significantly as a result of promoted formation of the "C"-styled conformation due to the monoprotonation of the peripheral pyridine units in 1 and 2. In contrast, the addition of 2 equiv of TFA substantially weakened the binding stability because the "S"-styled conformation was favored as a result of protonation of both of their pyridine units. Moreover, remarkable induced circular dichroisms were also displayed for the complexes of 1 and 2 with chiral D- and L- phenylalaninate.The third part involves the synthesis and characterization of the preorganized porphyrin-appended scaffolds along with chiral guests. A highly complicated compound, 49, (C507H536N40O31) has been prepared through totally over 30 steps, which started from simple starting material diamine and p-cresol. We herein chose folded aromatic amide oligomers as the building blocks for constructing the new assembled supramolecular host. Thus, pendant porphyrin units were introduced to the terminal benzene rings of the shape-persistent backbone, giving rise to dimer 31, trimer 41, tetramer 46 and heptamer 49. Owning to the presence of intramolecular hydrogen bonding, the porphyrin units in these molecules are arranged roughly parallel to each other. After metallization, these porphyrin hosts can efficiently recognize with pentafluorobenzamide-bearing N-ligands, as evidenced by the 1H NMR and UV-vis investigations.In the fourth part, the reactions of [60]fullerene with variousβ-dicarbonyl derivatives have been investigated in the presence of Mn(OAc)3·2H2O, which generated dihydrofuran-fused [60]fullerene derivatives or 1,4-bisadducts. Dihydrofuran-fused [60]fullerene derivatives could be produced by treatment ofα-unsubstitutedβ-diketones orβ-ketoesters with [60]fullerene in refluxing chlorobenzene in the presence of Mn(III). Solvent-participated unsymmetrical 1,4-bisadducts were obtained through the reaction of [60]fullerene with dimethyl malonate orα-substitutedβ-dicarbonyl compounds in toluene. A possible reaction mechanism for the formation of different fullerene derivatives is proposed.In the last part, the possibility of constructing [60]fullerene supramolecular polymers with rigid back-bone has been explored. SEM investigations revealed some interesting self-assembling processes.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Chemical kinetics
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