Fullerene Cages as Molecular Nanocontainers to Stabilize Unprecedented Uranium Clusters and Bonding Motifs

德克萨斯大学埃尔帕索分校的Luis Echegoyen和Skye Fortier教授得到化学系大分子，超分子和纳米化学计划的支持，以制备，纯化和表征新型铀基内嵌富勒烯。 目标是探索富勒烯笼中铀与其他原子（如碳、硫和氧）的基本键合性质。 富勒烯是一种完全由许多碳原子组成的化合物，这些碳原子键合在一起形成球形或伪球形封闭结构，在某些情况下类似于纳米尺寸的足球。 富勒烯是太阳能电池和光电子等材料应用中的重要组分。 这些富勒烯内部的空腔为研究具有不寻常结构和键合图案以及有趣的电子特性的孤立化学系统提供了独特的环境。金属或金属簇包埋在这些内嵌富勒烯内提供了稳定的纳米容器环境。 这使得独特和不寻常的铀簇的研究，将允许更好的基本和实际的理解，特别是铀的电子特性和一般的锕系元素系列。 该项目提供了一个进入富勒烯和锕系元素科学一个基本上新的分支的入口。 来自埃尔帕索得克萨斯大学的一群学生参与了该项目，埃尔帕索大学是一所少数民族服务机构。 鉴于该项目的合作性质，他们也接触到国际研究经验。 此外，还开发了几个针对中学，主要是西班牙裔理科学生的学习模块。 这个新的，一个月，20-25学生社区外展计划的目的是激发他们对科学的兴趣，同时发展批判性思维和解决问题的能力。本计画合成、纯化及分离一系列新型的含铀富勒烯。 预计这些碳笼纳米容器将允许访问不寻常的铀簇，并提供更好的基本了解锕系元素键合和化学。 初步结果的隔离和结构表征的非IPR（孤立的五角大楼规则）铀内面体，U@C80，这些分子的独特性和方法的可行性提供了无可争议的支持。 正在使用不同的反应器气体优化合成方法，同时正在测试烟灰提取条件以最大限度地提高产量。分离的化合物正在通过一整套技术进行研究，包括X射线晶体学分析，循环伏安法，电子和振动光谱，SQUID磁性分析和理论建模，以充分阐明其结构和性质。正在利用国家和国际合作来完成这些关键任务。这项工作为进入富勒烯和锕系元素科学的一个基本上新的分支提供了一个入口，预计将在这两个方面产生基础知识和新发现。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Professors Luis Echegoyen and Skye Fortier of the University of Texas at El Paso are supported by the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry to prepare, purify and characterize novel uranium-based endohedral fullerenes. The goal is to explore the fundamental bonding properties of uranium within the fullerene cage with other atoms such as carbon, sulfur, and oxygen. Fullerenes are chemical compounds composed exclusively of many carbon atoms that are bonded together to form spherical or pseudo-spherical closed structures, that in some cases resemble nano-sized soccer balls. Fullerenes are essential components in materials applications such as in solar cells and photovoltaics. The hollow cavities inside these fullerenes offer a unique environment to study isolated chemical systems with unusual structures and bonding motifs as well as interesting electronic properties. The entrapment of metals or metal clusters inside these endohedral fullerenes provides a stable nanocontainer environment. This enables the study of unique and unusual uranium clusters that will allow for a better fundamental and practical understanding of uranium electronic properties in particular and the actinide series of elements in general. The project provides an entryway into an essentially new branch of fullerene and actinide science. A group of students from the University of Texas at El Paso, which is a minority serving institution, are involved in the project. Given the collaborative nature of the project, they are also exposed to an international research experience. In addition, several learning modules, targeting middle school, mainly Hispanic science students, are developed. This new, one month, 20-25 student community outreach program is intended to stimulate their interest in science while developing critical thinking and problem-solving skills. In this project, a new series of uranium containing endohedral fullerenes is synthesized, purified and isolated. It is expected that these carbon caged nanocontainers will allow access to unusual uranium clusters and provide a better fundamental understanding of actinide bonding and chemistry. Initial results on the isolation and structural characterization of a non-IPR (Isolated Pentagon Rule) uranium endohedral, U@C80, provide incontrovertible support for the uniqueness of these molecules and the feasibility of the approach. The synthetic methodology is being optimized using different reactor gases, while soot extraction conditions are being tested to maximize the yield. The isolated compounds are being studied through a full battery of techniques that includes X-ray crystallographic analysis, cyclic voltammetry, electronic and vibrational spectroscopy, SQUID magnetic analysis, and theoretical modeling to fully elucidate their structures and properties. Both national and international collaborations are being leveraged to accomplish these critical tasks. This work provides an entryway into an essentially new branch of fullerene and actinide science and is expected to yield fundamental knowledge and new discoveries on both fronts.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.