Leveraging a Tetradentate Redox-active Ligand to Enhance Control Over Properties and Reactivity

With funding from the Chemical Synthesis Program in the Chemistry Division, Professor Alan Heyduk in the Department of Chemistry at the University of California, Irvine will explore the design and synthesis of redox-active ligand platforms that engender improved electronic properties and enhanced reactivity patterns in coordination complexes of transition metal ions. The project is motivated by the fact that the electronic properties and reactivity patterns of coordination complexes play a critical role in diverse areas of research such as the development of new photosensitive materials and the discovery of catalysts for synthesizing fuels and commodity and fine chemicals, respectively. To realize improved electronic properties and enhanced reactivity patterns, the research focuses on new ligand designs that offer tight control over the local coordination environment of the metal ion while also expanding the number of accessible oxidation state available to the metal ion. Collaboration with the SoCal Undergraduate Research Symposium at UCI provides research mentoring and guidance to undergraduate students, many from underrepresented groups, as they prepare to matriculate from graduate degree programs in STEM fields. This project centers on the development of tetradentate, redox-active ligands and the synthesis and characterization of their related transition-metal coordination complexes. The ligand design incorporates an ortho-phenylenediamine backbone that coordinates directly to the metal center and augments metal-based redox process due to its own three oxidation states that are accessible at mild potentials. Additionally, the ligand design incorporates two ancillary “arms” that also bind to the metal ion, providing stability and steric protection at the metal center and offer control over the local coordination environment. These ligand design features are deployed in two thrusts: (a) the development of ligand-to-ligand charge-transfer chromophores and (b) the development of catalysts for multi-electron, atom- and group-transfer reactions. In pursuing this project, the Heyduk group will utilize inorganic synthetic techniques to obtain new molecules for study. New complexes will be characterized by a battery of techniques including electrochemical methods, single crystal X-ray diffraction, NMR, EPR, UV-vis-NIR, and IR spectroscopies, as well as computational methods. Benefits and outcomes of the proposed work include an expanded understanding of how redox-active ligands can be used to control and enhance reactivity at transition metal ions and the training of a workforce skilled in the synthesis, characterization, and utilization of reactive coordination complexes. 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.