Synthesis Of Flexible Metallamacrocycles And Their Applications In Supramolecular Self-assembly

Reviewing the development of supramolecular chemistry, every time the emergence of new macrocyclic host compounds greatly promoted people’s understanding of different supramolecular effect phenomenon and the nature of intermolecular interactions. So the design and synthesis of novel macrocyclic compounds have become an important research subject in the study of supramolecular chemistry. A macrocycle with a pre-organizational circular conformation can effectively reduce the loss of the entropy in the process of the formation of an assembly structure (that is, the macrocyclic effect), thereby easily combining to a guest molecule with a large binding constant. From the1960s, the systematic research on the crown ethers, spherands, cryptands, cyclodextrins, calixarenes and cucurbiturils continually drove the study of macrocyclic chemistry to a higher and broader level. Since the1990s, coordination self-assembled macrocyclic compounds have been found to possess numerous advantages such as high efficiency of synthesis, diversity of product structure, and important applications in some aspects of catalysis, photoelectricity materials etc. Therefore these coordination-driven self-assembled macrocycles attracted enormous attention of chemists in recent years. Most of these macrocyclic compounds were built by using rigid organic ligands to combine with metal centers with specific coordination configurations, thus yielding rigid structures. In contrast, the synthesis of flexible macrocycles has been a formidable challenge due to more significant entropy lost in the synthesis process. In this paper, we mainly focus on the designed synthesis of flexible metal-organic macrocyclic molecules using coordination self-assembled strategy, and attempt to explore unique recognition and assembly performance of these flexible macrocycles relative to the rigid ones.N-heterocyclic carbenes (NHC) and coinage metal (Cu, Ag, Au) can form a strong coorditive bond with a high coordination bond energy. We thus developed a new strategy to use strong coordination ability to promote the synthesis of flexible metalla-macrocycles. We connected N-heterocyclic carbenes with pyridine fragments with different lengths to produce metalla-macrocycles with different sizes and multiple coordination sites. Nuclear magnetic resonance analysis showed that these macrocycles had good flexibility in solution. We also used single crystal diffraction method to study the structural characteristics of these macrocyclic molecules in detail.We further utilized the high metal-metal affinity between group11metal ions to decorate the surface of gold nanoparticles via Au (Ⅰ) bridging macrocyclic compounds. This modification can improve the properties of gold nanoparticles to acquire stable gold nanoparticles in pH=2acid solution. Further research also suggested that gold nanoparticles modified by the Au(Ⅰ) metalla-macrocycles can interact with metal ions, which may provide a basis for the development of single metal-metal nanoparticle bifunctional catalytic system.