RUI: Extended Metal Atom Chain Complexes of Fe and Co Supported by a C3 Symmetric, Scaffolded Ligand Platform

在化学系化学合成项目的支持下，弗曼大学的Gary Guillet和阿巴拉契亚州立大学的Jefferson E. Bates将研究含有三个金属原子的一维链的新化合物，如铁和钴，其中金属原子由于彼此接近而形成键。这项研究将产生控制金属原子链周围环境的新分子，从而影响金属-金属相互作用。这些化合物将揭示金属原子之间究竟是如何相互作用的，以及单个金属的性质（如磁性）是否可以被预测地控制。为了实现这些目标，Guillet团队将设计和合成一系列新的化合物，并由合作者Jefferson Bates进行计算建模。Guillet小组的学生将在实验室环境中获得实践培训，同时学习正确的化学安全，以及如何使用先进的仪器合成和表征化合物。在贝茨小组工作的学生将获得利用计算机预测新化合物性质的经验，以及如何将这些预测与吉列小组获得的实验可测量值进行比较。弗曼大学和阿巴拉契亚州立大学的本科研究经历往往是学生真正了解未来在科学、技术、工程和数学（STEM）领域工作所需要的关键时刻。来自吉列和贝茨小组的学生将获得与他们感兴趣的领域相关的培训和经验，并将为未来在化学科学领域的职业生涯做好更好的准备。铁和钴的新型扩展金属原子链（EMAC）配合物的发展对于理解不同配位几何下金属-金属键的性质以及影响这些有趣体系物理性质的因素具有重要意义。通过控制中心三金属核周围的配体框架，可以合理地设计出具有各种高自旋基态电子构型的EMACs。过去的合成策略使用三个立体阻碍桥接配体，如2,6-二（三甲基硅胺）吡啶，以包围和稳定三金属核心。然而，由于需要低配位数的环境才能产生高自旋，因此孤立配合物缺乏稳定性，阻碍了合成大量高自旋三金属EMACs的努力。这一提议验证了一个假设，即建立在包含所有供体原子的c3对称支架上的配体将能够更好地支持铁和钴的三金属EMACs，并且这些配合物将具有更高的稳定性。利用简单的胺化反应，2,6-二溴吡啶将与伯胺官能化，并在第二次胺化反应中附着在支架分子上。锂化和变形步骤将形成铁和钴的三金属EMACs。结合实验测量，这些金属-金属键的性质将通过使用密度泛函理论和多构型波函数理论的计算方法来探索。一个扩展的更稳定的EMACs库将有助于增加对多个直接金属-金属键和导致高自旋磁基态的因素的理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Synthesis program in the Division of Chemistry, Gary Guillet of Furman University and Jefferson E. Bates of Appalachian State University will study new chemical compounds containing one dimensional chains of three metal atoms, such as iron and cobalt, where the metal atoms form bonds with each other due to their proximity. This study will produce new molecules that control the environment around the chain of metal atoms therefore influencing the metal-metal interactions. These compounds will shed light on how exactly metal atoms interact with each other and if the properties, such as the magnetism, of the individual metals can be predictably controlled. To accomplish these goals, the Guillet team will design and synthesize a series of new compounds supported with computational modeling performed by collaborator Jefferson Bates. Students in the Guillet group will gain hands-on training in a laboratory setting while learning proper chemical safety, and how to synthesize and characterize chemical compounds using advanced instrumentation. Students working in the Bates group will gain experience utilizing computers to predict the properties of new compounds and how to compare those predictions with the experimental measureables obtained in the Guillet group. The undergraduate research experience at both Furman and Appalachian State is often a crucial time when students truly get to know what a future working in a science, technology, engineering, and mathematics (STEM) field entails. The students from both the Guillet and Bates groups will gain pertinent training and experience for their fields of interest and are will be better prepared to pursue a future career in chemical sciences.The development of new extended metal atom chain (EMAC) complexes of iron and cobalt is important for understanding the nature of metal-metal bonding in varying coordination geometries and the factors that affect the physical properties of these interesting systems. By controlling the ligand framework around the central trimetallic core it may be possible to rationally design EMACs with various high-spin ground state electronic configurations facilitated by small intermetallic distances. Past synthetic strategies used three sterically encumbering bridging ligands, such as 2,6-bis(trimethylsilylamino)pyridine, to surround and stabilize the trimetallic core. However, efforts to synthesize a broad array of high spin trimetallic EMACs have been hampered by the lack of stability of the isolated complexes since low coordination number environments are needed to engender high spin. This proposal tests the hypothesis that ligands built upon a C3-symmetric scaffold that incorporates all the donor atoms will be better able to support trimetallic EMACs of Fe and Co and that these complexes will have increased stability. Utilizing simple amination reactions, 2,6-dibromopyridine will be functionalized with a primary amine and in a second amination reaction attached to a scaffolding molecule. Lithiation and transmetallation steps will form trimetallic EMACs of Fe and Co. In combination with experimental measurements, the nature of these metal-metal bonds will be explored through the use of computational methods from density functional theory and multiconfigurational wavefunction theories. An expanded library of more stable EMACs will help to build increased understanding of multiple direct metal-metal bonds and the factors that lead to high-spin magnetic ground states.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.