(3+3) Schiff-base metallomacrocycles and their aggregation in solution

• Main Author: Ma, Tsz Lui Cecily
• Format: Others
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/16266

Conjugated macrocycles are attractive precursors to new materials such as porous solids, synthetic ion channels, catalysts and other supramolecular materials. The development of these cyclic molecules for applications has been limited by the synthetic difficulties inherent in assembling a complex molecule. Imine formation by the condensation of an amine and an aldehyde is a convenient method for assembling large molecules. Since this reaction is reversible, macrocycles can be obtained under thermodynamic control. Large shape-persistent conjugated macrocycles (14-16) with tunable pore diameters in the nanometer regime were prepared by employing Schiff-base chemistry without the necessity of an added template. These new self-assembled macrocycles contain three N₂O₂ pockets, which can bind to multiple metal ions (e.g. Zn²⁺), forming soluble luminescent complexes (17 and 18a). The fluorescence of the macrocycles (14-16) could also be quenched by the coordination of metal ions (e.g. Ni²⁺ , Cu²⁺) in the three N₂O₂ pockets. The aggregation behaviour of the zinc metallated macrocycles (17 and 18a) in solution was investigated by ¹H NMR, absorption and fluorescence spectroscopies. It was discovered that solvent can play a crucial role in the association of the metallomacrocycles. The macrocyclic assemblies can sense coordinating bases, which cause deaggregation of the supramolecular assemblies. The aggregation was not disrupted by polar solvents, suggesting the association of the metallomacrocycles involved an additional interaction, Zn—O coordination, rather than solely hydrogen bonding or π-stacking of aromatic units. === Science, Faculty of === Chemistry, Department of === Graduate