Ditopic Chelating Chiral Pyridine Ligands for Coordination Polymers, Metallogrids and Metallomacrocycles

雙配位模式螯合手性吡啶配體的配位聚合物 、金屬格狀以及金屬大環配合物

Student thesis: Doctoral Thesis

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Author(s)

  • Luwei LI

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date23 Dec 2015

Abstract

Four different ditopic chelating chiral pyridine ligands were synthesized and used to form coordination supramolecular assemblies. A general introduction of coordination supramolecules with special focus on three types of supramolecules, coordination polymer, metallogrid and metallomacrocycle are presented in Chapter 1.
In Chapter 2, the preparation of two chiral ditopic pyridyl-imine ligands L1, L2 and their Ag(I) complexes, 1 and 2 are presented. Both complexes resulted from the reaction of the ligands and Ag(I) in molar ratio of 1 to 1 are chiral 1D coordination polymers. 1 and 2 have been characterized by ESI-MS, elemental analysis, NMR and CD spectroscopy. The structures of 1 and 2 have also been successfully characterized by X-ray diffraction analysis. In the two polymers, Ag(I) centers are all in a tetrahedral coordination geometry, but they exhibit very different structures and properties. 1 is a helical coordination polymer with all Δ configured metal centers and 2 is a zigzag coordination polymer with alternated Δ- and Λ-configured metal centers. The zigzag coordination polymer dissolves in CH2Cl2. While the helical coordination polymer forms a metallogel in CH2Cl2, which exhibits visual chiral recognition property of amine enantiomers by gel collapsing.
In Chapter 3, the synthesis of dipyridyl hydrazide imine ligands HL3 and its Zn(II) complexes are presented. The self-assembly of Zn(II) with HL3 in a ratio of 1 to 1 gives two tetranuclear [2 × 2] metallogrid complexes, 3 and 4, which can be separated as a pair of pseudoenantiomers under different conditions. They have been successfully characterized by ESI-MS, elemental analysis, NMR, CD spectroscopy as well as X-ray diffraction analysis. The results show that two octahedral Zn(II) centers with Λ configuration in 3 have labile cis-position coordination sites, while for the pseudoenantiomeric 4, the corresponding metal centers have opposite Δ configuration. The two pseudoenantiomers complexes can “racemize” into each other by adjusting the solvent condition and they both exhibit enantioselective catalytic properties to ring-opening reactions.
In Chapter 4, the synthesis of dipyridyl hydrazide imine ligands HL4 and its Cu(II) complexes are presented. With different anions, such as ClO4−, BF4−, PF6− or SbF6−, the reaction of HL4 and Cu(II) gives a octanuclear metallomacrocycle 5. But with Cu(OTf)2, the reaction gives a decanuclear metallomacrocycle 6. Both 5 and 6 have been structurally characterized by X-ray diffraction analysis. One anion is captured in the cavity of both types of metallomacrocycles. Anion exchange studies have been carried out for 5. For 6, it is stable only in methanol. Changing the solvent from methanol to nitromethane induce conversion from 6 to 5. The conversion is reversible when the solvent is changed back to methanol.