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

在化学系化学合成计划的支持下，弗曼大学的Gary Guillet和阿巴拉契亚州立大学的Jefferson E.Bates将研究包含三个金属原子的一维链的新化合物，例如铁和钴，这些金属原子由于接近而相互结合。这项研究将产生新的分子来控制金属原子链周围的环境，从而影响金属与金属的相互作用。这些化合物将揭示金属原子之间到底是如何相互作用的，以及是否可以预测地控制每种金属的性质，如磁性。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，并由合作者杰斐逊·贝茨进行计算建模。Guillet小组的学生将在实验室环境中接受实践培训，同时学习适当的化学安全，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的性质以及如何将这些预测与Guillet小组获得的实验测量数据进行比较的经验。福尔曼和阿巴拉契亚州立大学的本科生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)领域工作的关键时刻。来自Guillet和Bates小组的学生将获得他们感兴趣的领域的相关培训和经验，并将为未来在化学科学中的职业生涯做好更好的准备。开发新的扩展金属原子链(EMAC)铁和钴的络合物对于理解不同配位几何中金属-金属键的性质以及影响这些感兴趣的体系的物理性质的因素非常重要。通过控制中心三金属核周围的配体骨架，可以合理地设计具有各种高自旋基态电子组态的Emacs，这些电子组态可以通过小的金属间距离来实现。过去的合成策略使用三种空间封闭的桥联配体，如2，6-双(三甲基硅氨基)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，孤立的络合物缺乏稳定性，阻碍了合成广泛的高自旋三金属EMAC的努力。这一建议验证了一种假设，即建立在C3对称支架上的配体将能够更好地支持Fe和Co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，然后在连接到支架分子上的第二胺化反应中。锂化和过渡金属步骤将形成Fe和Co的三金属键。结合实验测量，将利用密度泛函理论和多组态波函数理论的计算方法来探索这些金属-金属键的性质。更稳定的Emacs库的扩展将有助于加深对多个直接金属-金属键和导致高自旋磁性基态的因素的理解。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。

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.