Photocatalyst size controls electron and energy transfer: selectable E/Z isomer synthesis via C-F alkenylation.

Photocatalytic alkene synthesis can involve electron and energy transfer processes. The structure of the photocatalyst can be used to control the rate of the energy transfer, providing a mechanistic handle over the two processes. Jointly considering catalyst volume and emissive energy provides a highly sensitive strategy for predicting which mechanistic pathway will dominate. This model was developed en route to a photocatalytic Caryl-F alkenylation reaction of alkynes and highly-fluorinated arenes as partners. By judicious choice of photocatalyst, access to E- or Z-olefins was accomplished, even in the case of synthetically challenging trisubstituted alkenes. The generality and transferability of this model was tested by evaluating established photocatalytic reactions, resulting in shortened reaction times and access to complimentary Z-cinnamylamines in the photocatalytic [2 + 2] and C-H vinylation of amines, respectively. These results show that taking into account the size of the photocatalyst provides predictive ability and control in photochemical quenching events.