| Autor: |
Bawden JC; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia., Francis PS; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia., DiLuzio S; Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States., Hayne DJ; Institute for Frontier Materials, Deakin University, Geelong, Victoria 3220, Australia., Doeven EH; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia., Truong J; School of Science, RMIT University, Melbourne, Victoria 3000, Australia., Alexander R; Centre for Regional and Rural Futures, Deakin University, Geelong, Victoria 3220, Australia., Henderson LC; Institute for Frontier Materials, Deakin University, Geelong, Victoria 3220, Australia., Gómez DE; School of Science, RMIT University, Melbourne, Victoria 3000, Australia., Massi M; School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia 6102, Australia., Armstrong BI; School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia 6102, Australia., Draper FA; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia., Bernhard S; Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States., Connell TU; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia. |
| Abstrakt: |
Photoredox catalysts are primarily selected based on ground and excited state properties, but their activity is also intrinsically tied to the nature of their reduced (or oxidized) intermediates. Catalyst reactivity often necessitates an inherent instability, thus these intermediates represent a mechanistic turning point that affords either product formation or side-reactions. In this work, we explore the scope of a previously demonstrated side-reaction that partially saturates one pyridine ring of the ancillary ligand in heteroleptic iridium(III) complexes. Using high-throughput synthesis and screening under photochemical conditions, we identified different chemical pathways, ultimately governed by ligand composition. The ancillary ligand was the key factor that determined photochemical stability. Following photoinitiated electron transfer from a sacrificial tertiary amine, the reduced intermediate of complexes containing 1,10-phenanthroline derivatives exhibited long-term stability. In contrast, complexes containing 2,2'-bipyridines were highly susceptible to hydrogen atom transfer and ancillary ligand modification. Detailed characterization of selected complexes before and after transformation showed differing effects on the ground and excited state reduction potentials dependent on the nature of the cyclometalating ligands and excited states. The implications of catalyst stability and reactivity in chemical synthesis was demonstrated in a model photoredox reaction. |
