Constructing Endohedral Fullerenes Using Open-Cage Fullerenes and Heterofullerenes

加州大学戴维斯分校的Alan L.Balch和Marilyn M.Olmstead教授在化学系大分子、超分子和纳米化学计划的支持下，开发了制备面内富勒烯(包裹金属离子的纳米足球状碳笼)的新方法。合成方法的设计是为了仔细和选择性地控制金属原子插入富勒烯，在那里原子将得到稳定。在气相过程中，只有少量的面内富勒烯被制备。他们已经在医学成像技术方面展示了希望，如磁共振成像(MRI)造影剂(使用顺磁性Gd)和X射线造影剂(使用强X射线吸收剂钚)。该项目的重点是开发大量制备内面体富勒烯的新方法，以促进其在诊断、医学成像和其他可能的技术应用中的实际应用。大学和高中的学生参与了这个项目，并接受了最先进的合成和结构表征技术的培训。正在开展若干外联活动，包括化学同行指导方案和研讨会课程，如“艺术和科学中的对称性”和“化学品及其对加利福尼亚州历史的影响”。在这个项目中，已知的化学程序被用来在C60和C70的富勒烯笼子的织物上形成孔，以形成开笼富勒烯。这些开放的笼子结构经常在孔口附近具有适合于金属离子键合的Lewis碱基。随后，金属离子被连接到这些开笼富勒烯上，并最终插入到它们的内部。笼子的缩小被用来吸引金属离子通过开口进入内部。用光谱学方法对这些反应进行了监测，并对产物进行了分离和结构表征，特别是用单晶X射线衍射法对产物进行了表征，其中包括开笼富勒烯与金属离子在内外的金属离子配合物。一旦金属中心进入笼子，就会通过化学反应开始封闭富勒烯网络中的空洞。将检查新的内体物种的物理性质，如作为MRI造影剂和X射线造影剂的能力。该项目还设计了两条新的合成路线，以制造宏观数量的金属杂富勒烯，即碳笼，其中一些碳原子被金属原子取代。这类金属杂富勒烯以前从未作为固体获得过，可以通过光谱和X射线结晶学手段进行表征。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Professors Alan L. Balch and Marilyn M. Olmstead of the University of California-Davis are supported by the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry to develop new methods for the preparation of endohedral fullerenes (nano-sized soccer ball-like carbon cages encapsulating metal ions). The synthetic methods are designed to carefully, and selectively, control the insertion of metal atoms into fullerenes, where the atom will be stabilized. Endohedral fullerenes have only been prepared in minute quantities in a gas phase process. They have already shown promise in medical imaging technology as magnetic resonance imaging (MRI) contrast agents (using paramagnetic gadolinium) and X-ray contrast agents (using the strong X-ray absorber lutetium). The project is focused on the development of new methods for the preparation of endohedral fullerenes in large quantities to facilitate their practical use for such diagnostic medical imaging and other possible technological applications. Students at college and high school levels are involved in the project and trained in state of the art synthetic and structure characterization techniques. Several outreach activities, including a chemistry peer mentoring program, and seminar courses, such as " Symmetry in Art and Science" and "Chemicals and their Effect on California History" are being developed. In this project, known chemical procedures are used to fashion holes in the fabric of the fullerene cages of C60 and C70 to form open-cage fullerenes. These open cage structures frequently have Lewis base sites suitable for metal ion bonding near the orifice. Subsequently, metal ions are attached to these open cage fullerenes and eventually inserted into their interior. Reduction of the cage is used to attract the metal ion through the opening and into the interior. These reactions are monitored by spectroscopic means and the products, including metal ion complexes of the open cage fullerenes with metal ions on the outside and on the inside, are isolated and structurally characterized, particularly by single crystal X-ray diffraction. Once the metal center enters the cage, chemical reactions are used to begin to close the hole in the fullerene network. Physical properties, such as ability to function as MRI contrast agents and X-ray contrast agents, of the new endohedral species will be examined. The project is also designed to examine two new synthetic routes to make macroscopic amounts of metallo-heterofullerenes, carbon cages with some of the carbon atoms replaced with metal atoms. Such metallo-heterofullerenes have never previously been obtained as solids that can be characterized through spectroscopic and X-ray crystallographic means.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.