Functionalized macrocyclic ligands for use in supramolecular chemistry.
The synthesis of three cross-conjugated macrocycles bearing pyridine functionality is described. The ability of two of these molecules, 5a and 5c, to behave as 4,4'-bipyridine mimics in self-assembly reactions is demonstrated by axial coordination to a metalloporphyrin. The directed coordinative ability of the pyridine rings ensures predictable self-assembly into well-ordered nanoscale systems, both in solution and the solid state. 1H, 13C, and HMQC NMR spectroscopic experiments and ESI MS have been used to characterize the supramolecular complexes in solution. X-ray crystallographic analysis of solid-state assemblies 7a and 7c provides insight into the scope and flexibility of these macrocyclic ligands as supramolecular building blocks. UV-vis and fluorescence spectroscopies provide a description of their electronic characteristics.