Electric Field-Mediated Reactivity of Metalloporphyrin Complexes Immobilized at SAM/Electrolyte Interfaces

Auburn University, Auburn AL

Investigators

Abstract

In this project, funded by the Chemical Mechanism, Function, and Properties Program of the Chemistry Division, Professors Ethan Hill and Paul Ohno of the Department of Chemistry and Biochemistry at Auburn University are investigating the use of externally-applied electric fields (E-fields) in transition metal catalysis with the ultimate goal of developing new “switchable” catalysts for advanced chemical synthesis. The tight collaboration between a primarily synthetic inorganic research group and primarily experimental physical chemistry group will enable students to receive broad training across the chemical discipline and prepare them for success in the modern research landscape where societal grand challenges require large collaborative efforts across traditional scientific disciplines. Finally, a tiered approach has been developed with appropriate activities for educating and engaging with high school students, college students, and the general public through this work and related scientific topics. Metalloporphyrin catalysts have been immobilized onto gold electrodes at a specific orientation using a self-assembled monolayer (SAM). Using an applied E-field, properties and ligand exchange dynamics around the transition metal center will be altered to influence chemistry. A combination of electrochemical techniques and vibrational sum frequency generation (SFG) spectroscopy will be used to monitor in situ changes at the metal center and connect these changes to observed reactivity. Using vibrational handles present in the SAM linkers and on certain ligands, shifts in peak position and intensity will be used to determine the strength of the local E-field and investigate the local electrostatic environment at the metal center in order to carry out the following objectives: 1) Quantify local E-field effects on the reactivity of an immobilized Ru-porphyrin 2) Determine the influence of transition metal identity on E-field driven reactivity 3) Elucidate inductive vs. through-space effects in E-field driven reactivity. Altogether, completion of these objectives will advance our understanding of the quantitative connection between applied E-field and chemical reactivity in transition metal complexes and how this connection is influenced by chemical properties and chemical structure. 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.