基于碗烯的金属配位超分子笼的构筑及其性能研究

In nature, biological encapsulants achieve their selective separation and stabilization of labile species by providing isolated microspace within the molecules. Over the past few decades,a variety of synthetic molecules with enclosed well-defined cavity have been developed to mimic the structure of their natural counterparts but most of them possess a very complicated structure which is hard to fabricate or a small cavity which restrict its application in reaction chamber and drug delivery. Due to the bowl shape, rigid polycyclic aromatic nature and 5-fold symmetry structure of corannulene, we propose here to use corannulene as a building block to fabricate a serials of molecular cages through metal-induced self-assembly. Some corannulene-based heterometal coordination cages will be also prepared. We'll initially monitor the self-assembly process and fully charactrize the structures of the cages in solutions as well as those in the solid state. The relationship between the properties of cages and the characters of corannulene-based ligands, the metal ions as well as the solvents will be found out. Due to their well-defined cavities, the cages are promising to encapsulate some kinds of guest molecules inside their frameworks. We'll testify the interaction between the cages and the guests, find out their binding models and affinities, and more importantly, ascertain that those capsules are characterized by kinetic stability or thermodynamic stability. To fully understand how the interaction works and to guide further development of huge molecular cages used for drug delivery, the characters of the cavities of the cages and the guest molecules will be carefully analyzed. The stabilization of reactive intermediates is a unique property of molecular capsules. We'll prepared an unstable carbazyl and try to use the corannulene-based cages to stabilize the carbazyl by preventing their dimerization or obtaining active protons from the circumstance. We'll also study the behavior of the carbazyl in such safe closed microspace. Since there is yet no artificial molecular cages which were prepared based on big , bowl-shap aromatic molecules to date, we believe that the results which will be produced from this project will highlight the broader strategy of fabrication of molecular cages and be of great interest to a broad range of organic, bioorganic, structural and supramolecular chemists.

笼状结构在生物的隔离免疫、物质与能量储存等方面发挥重要作用。人工分子笼试图在分子层面模拟和理解生物分子笼的性质和功能。本项目针对现有大多数人工分子笼体系构筑复杂、笼尺寸难以调节、或者空腔较小等不足，拟通过对易于功能化的曲面分子碗烯进行修饰，通过自组装构筑一系列具有不同空腔形状与尺寸的碗烯基金属配位分子笼。本项目拟利用多种手段，研究该型配位分子笼的自组装行为和结构，认识和了解碗烯基配体的种类、金属离子以及溶剂对自组装结构的影响；研究分子笼对客体分子的包络行为，分析分子笼与客体分子相互作用的基本规律、络合热力学以及主客体作用在动力学上的稳定性来源。本项目还拟利用该型分子笼研究不稳定氮自由基在密闭微环境中的衰变行为，探讨分子笼用于存放不稳定自由基的可行性。由于到目前为止，还没有基于大曲面结构构筑人工分子笼报道，预期本项目的研究成果将扩展现有人工分子笼的种类，为未来深入研究分子笼的性质提供思路。

分子笼是一种具有三维内空腔的笼状分子或超分子体系,其在物质分离、分子反应器等领域具有巨大的应用价值。科学界迄今已发展出许多种人工分子笼体系，但还没有基于曲面芳香体系的分子笼研究。着眼于对这种分子笼特性的理解和其功能的开发，本项目围绕碗烯基配位分子笼展开，研究了金属离子和双齿配体间的配位特征，设计并首次合成出一系列碗烯衍生物配体，研究了这些配体与金属离子的配位自组装，筛选并最终构筑出三类结构明确的M5L2型分子笼。我们研究了所得笼的结构特性及其与客体分子的相互作用规律，并初步探索了这些分子笼的应用。总体上，所得碗烯基分子笼能较好的包络球形或类球形客体分子，对其他类型分子则几乎没有包络能力。由于碗烯的天然动态手性以及银离子动态配位的特点，五-(3-吡啶基)碗烯-Ag(I)配位分子笼具有特殊的构象多样性，并且在手性阴离子的诱导下形成手性分子笼。特别是，该笼的这种构象多样性可以提供一种分子区分和鉴定的新途径。具有更大空腔的五吡啶基炔基碗烯配位分子笼能选择性包络低级富勒烯如C60和C70，但对C60具有更强的络合能力，从而可以依靠设计的路线对烟灰中的C60和C70进行高效分离。五联吡啶基碗烯能够形成银配位及汞配位的分子笼，这两种分子笼间能可逆互变但对客体分子的包络具有不同的溶剂依赖性，从而创造了一种由溶剂和金属离子双重控制的客体分子释放途径。该部分工作首次详细的探索了基于具有高对称性的大曲面芳香体系的超分子笼的构建，初步揭示了该类型分子笼区别于传统的基于直线、折线以及平面形配体分子笼的一些特性，为下一步扩展该型分子笼的应用打下一定基础。上述结果已在国外核心刊物上发表论文8篇。