嵌于大碳笼富勒烯内的双钇原子是金属原子对还是金属碳化物?

Dimetallofullerenes could be classified to two types in line with that whether metal atom pairs or metal carbide clusters are encapsulated into carbon cages. This project aims to the investigation of diyttrium metallofullerenes with large carbon cages. On the basis of high yield synthesis, a series of pure diyttrium metallofullerenes would be successfully isolated. Their molecular structures would be characterized by nuclear magnetic resonance and X-ray single crystal diffraction techniques with the assistance of molecular orbitals and molecular dynamics calculations, and then it would be clarified whether yttrium atomic pairs or yttrium carbide clusters were trapped inside large fullerene cages. The cycloaddition reaction towards the fullerene cages of diyttrium metallofullerenes would be carried out by reagents and solvents with varying ability to donate electrons. With a variety of cycloaddition adducts available, the mutual relations between the additive groups outside the cage and the rotation of yttrium atom pairs or yttrium carbide clusters inside would be studied. It is conjectied that the size of carbon cages has some effects on their strctures and chemical reactivities of the above two types of dimetallofullerenes as well as the dynamic behaviors of yttrium atomic pairs or yttrium carbide clusters trapped inside carbon cages.Investigation on the spectroscopic and electromagnetic properties of dimetallofullerenes and their cycloaddition adducts might lead to their application to the field of new energy. It is very important to clarify their molecular structure for the discussion of formation mechanism and for the selective synthesis of the above two types of dimetallofullerenes. Moreover, a variety of cycloaddition adducts will not only enrich the chemistry of endohedral metallofullerenes, but also will lay the foundation for their applications in optoelectronic devices and biomedicals.

双金属富勒烯按照碳笼内是否嵌入碳原子可分为内嵌金属原子对和内嵌金属碳化物两种类型。本课题拟在成功分离出双钇金属富勒烯系列纯品的基础上，利用核磁共振和X射线单晶衍射技术并结合理论计算与动力学模拟对其分子结构进行表征，阐明双钇原子是以金属原子对还是以金属碳化物的形式嵌于大型富勒烯碳笼内的科学问题；选择授电子能力不同的试剂和溶剂进行环加成反应，建立笼外基团与内嵌双钇金属原子对或内嵌双钇金属碳化物团簇运动状态的相互关系；尝试总结碳笼大小对两类双钇金属富勒烯的结构、化学稳定性及内嵌金属原子对或内嵌金属碳化物团簇在碳笼内的动力学行为等方面的影响规律；研究它们的光谱学和电磁学性质，考察将它们应用于新能源领域的可能性。查明两类双金属富勒烯的分子结构对探讨其形成机制和实现其选择性合成都是非常重要的，而对它们进行多种化学修饰，不但会丰富内嵌金属富勒烯化学，而且也将为它们在光电子器件和生物医学中的应用奠定基础。

双金属富勒烯按照碳笼内是否嵌入碳原子可分为内嵌金属原子对和内嵌金属碳化物两种类型。本课题采用直流电弧放电合成和高效液相色谱分离的方法，成功获得了包括内嵌双钇金属富勒烯在内的系列纯品。利用MALDI-TOF MS、分析型HPLC、UV-vis-NIR、CV和DPV等表征手段并且结合理论计算，系统地研究了它们的电子结构和分子结构，阐明了双金属，特别是双钇原子，是以金属原子对还是以金属碳化物的形式嵌于大型富勒烯碳笼内的科学问题；开展了一系列内嵌金属富勒烯的加成反应，通过对比加成产物与反应物在电子光谱上的异同并结合理论计算，确定了反应物在富勒烯碳笼上的加成方式（开环加成还是闭环加成）和加成位置（[5,6]还是[6,6]加成）；对部分分离纯化的内嵌金属富勒烯和内嵌金属富勒烯加成产物的电化学性质研究表明：内嵌金属富勒烯加成产物的氧化还原电位比对应内嵌金属富勒烯的更低一些，它们是更好的电子授体材料；利用有机溶剂中共结晶法和界面扩散法分别成功培养了Tb@CS-C82和Pr@C2V(9)-C82Ad的单晶体。晶体结构解析表明：Tb@Cs(6)-C82分子之间通过C-C单键连接形成了二聚体结构，在Pr@C2V(9)-C82Ad中重氮金刚烷是以[6,6]开环加成的方式加成在离内嵌镨原子最近的C=C双键上的；利用理论化学计算阐明了内嵌金属富勒烯（Pr@C72和Pr@C74）和加成产物（C72(C6H3Cl2) 、C74(C6H3Cl2)和Pr2@C72Ad）的异构体结构、相对稳定性和热力学几率分布，以及Pr原子与碳笼之间的电子转移与轨道相互作用等科学问题。