| Autor: |
Draper F; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia., DiLuzio S; Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States., Sayre HJ; Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States., Pham LN; Institute for Nanoscale Science and Technology, Flinders University, Adelaide, South Australia 5042, Australia., Coote ML; Institute for Nanoscale Science and Technology, Flinders University, Adelaide, South Australia 5042, Australia., Doeven EH; 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., Connell TU; School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia. |
| Abstrakt: |
Photoredox catalysis is a powerful tool to access challenging and diverse syntheses. Absorption of visible light forms the excited state catalyst (*PC) but photons may be wasted if one of several unproductive pathways occur. Facile dissociation of the charge-separated encounter complex [PC •- :D •+ ], also known as (solvent) cage escape, is required for productive chemistry and directly governs availability of the critical PC •- intermediate. Competitive charge recombination, either inside or outside the solvent cage, may limit the overall efficiency of a photochemical reaction or internal quantum yield (defined as the moles of product formed per mole of photons absorbed by PC). Measuring the cage escape efficiency (ϕ CE ) typically requires time-resolved spectroscopy; however, we demonstrate how to estimate ϕ CE using steady-state techniques that measure the efficiency of PC •- formation (ϕ PC ). Our results show that choice of electron donor critically impacts ϕ PC , which directly correlates to improved synthetic and internal quantum yields. Furthermore, we demonstrate how modest structural differences between photocatalysts may afford a sizable effect on reactivity due to changes in ϕ PC , and by extension ϕ CE . Optimizing experimental conditions for cage escape provides photochemical reactions with improved atom economy and energy input, paving the way for sustainable design of photocatalytic systems. |
