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Abstract Triplet‐triplet annihilation photon upconversion (TTA‐UC) converts low‐energy photons to higher‐energy ones under low‐intensity incoherent excitation, thus enabling applications in fields ranging from medicine to solar energy conversion. Silylethynyl mono‐ and di‐substitution of acenes offers an attractive route to creating new annihilators that operate with minimal energy loss. Here, it is demonstrated that this approach can be extended to pyrene, yielding annihilators that display efficient red‐to‐blue upconversion. While pyrene is the namesake of P‐type delayed fluorescence, the original name for triplet‐triplet annihilation, it is known to be a poor annihilator due to its propensity for forming excimers. By tetra‐substituting pyrene with silylethynyl groups, excimer formation is substantially hindered while simultaneously minimizing the energy gap between the singlet and triplet pair states that participate in TTA‐UC, yielding outstanding annihilators for red‐to‐blue upconversion that operate with quantum yields of upward of 19% (29% when corrected for inner filter effects). Further, it is found that reducing the bulkiness of the silyl substituents is key to achieving high TTA‐UC quantum yields, which highlights the importance of annihilator side group selection when optimizing photon upconversion. 

Abstract The use of visible light to drive polymerizations with spatiotemporal control offers a mild alternative to contemporary UV‐light‐based production of soft materials. In this spectral region, photoredox catalysis represents the most efficient polymerization method, yet it relies on the use of heavy‐atoms, such as precious metals or toxic halogens. Herein, spin‐orbit charge transfer intersystem crossing from boron dipyrromethene (BODIPY) dyads bearing twisted aromatic groups is shown to enable efficient visible light polymerizations in the absence of heavy‐atoms. A ≈5–15× increase in polymerization rate and improved photostability was achieved for twisted BODIPYs relative to controls. Furthermore, monomer polarity had a distinct effect on polymerization rate, which was attributed to charge transfer stabilization based on ultrafast transient absorption and phosphorescence spectroscopies. Finally, rapid and high‐resolution 3D printing with a green LED was demonstrated using the present photosystem. 

Efficient near-infrared (NIR) photopolymerization is promising for applications such as hydrogel bioprinting, composite manufacturing, and other technologies that benefit from deep light penetration and low-energy activation. Yet, design principles for... 

A series of thiophene-fused boron dipyrromethene (BODIPY) photoredox catalysts are systematically examined to identify structure–reactivity relationships that enable efficient near-infrared light-induced polymerizations.