Triplet Energy Transfer Photocatalysis: Unlocking the Next Level

Photoinduced Hydroarylation and Cyclization of Alkenes with Luminescent Platinum(II) Complexes

“…From energy consideration, an exergonic reverse TTEnT event from 3 d1* to Pt‐2 with a considerably higher rate constant than the forward TTEnT would be more favorable. Thus, the possibility of occurrence of a reversible EnT dynamics leading to a diminished 3 d1* population cannot be excluded [23b] . In this scenario, the ensuing radical ring closure step has to be much faster than the reverse TTEnT process and/or irreversible to drive the productive reaction forward.…”

“…A recent work by Guldi and Glorius demonstrated an efficient [2+2]-photocycloaddition of benzothiophene involving an endergonic TTEnT step of 5.77 kcal mol À1 from an Ir III -photosensitizer to benzothiophene. [23] It is conceived that similar photo-coupled-thermally activated TTEnT mechanism between Pt-2* and d1 could also be operative. Addition of TEMPO as triplet quencher inhibited the reaction and the starting materials were recovered, lending support to an EnT mechanism.…”

Stereoselective Synthesis of Cyclohepta[b]indoles by Visible‐Light‐Induced [2+2]‐Cycloaddition/retro‐Mannich‐type Reactions

“…This indicates that excited-state FCNIrpic activates the substrate solely by interacting with the enaminone moiety. To prove that the enaminone was activated via single electron oxidation [13a-p] instead of energy transfer, [21] we synthesized compound 20, and performed a comparative experiment (Figure 2 b). It shows that although the fluorescence of FCNIrpic could be quenched by enaminone 20, no reaction occurred when 20 was irradiated with blue LEDs in the presence of FCNIrpic.…”

Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

“…The capacity for organic TADF compounds to participate in triplet DET is dependent on the intersystem crossing quantum yield, F ICS , which describes the population of PCs in their triplet excited states. 85 Under the constant irradiation conditions employed in photocatalysis and given the long delayed lifetimes of most organic TADF PCs, there is sufficient population of triplet excitons to permit triplet sensitization reactions by organic TADF PCs. Additionally, it should be noted that DET is not limited to PEnT from triplet states, and can indeed occur from the singlet excited state.…”