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

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.