Angewandte Chemie International Edition最新文献

Sensitized organic photon upconversion via triplet-triplet annihilation (TTA) shows significant potential for energy conversion and photocatalysis, but achieving efficient upconversion across multiple wavelengths with single-wavelength near-infrared (NIR) excitation remains a daunting challenge. Here, we report a strategy utilizing lanthanide-doped nanocrystals (LnNCs) to sensitize TTA upconversion in multiple organic emitters under NIR excitation, achieving an anti-Stokes shift of up to 1.1 eV. This approach leverages a cascade lanthanide-triplet energy transfer design, adopting an interfacial energy transfer pathway via lanthanide ions to surface energy relay molecules for extended triplet sensitization. It allows consecutive transfer of photon energy from LnNCs to TTA emitters, mitigating energy mismatch between the triplet levels of emitters and excitation photon energies. The use of LnNCs enhances energy transfer efficiency through the unique spin-orbital coupling and narrow-band absorption properties of lanthanide ions. Our approach offers tunable upconversion emission, minimized energy loss during sensitization, and improved chemical stability of LnNCs. Additionally, we demonstrate the utility of this system in NIR-induced photopolymerization, showcasing its potential for applications such as 3D printing and photocatalysis.

Regioselective and enantioselective C-H functionalization is a valuable method for synthesizing chiral and complex molecules. However, it often requires large amounts of toxic oxidants and high temperature, making it environmentally and economically adverse. Additionally, these traditional approaches generally suffer from regioselectivity and enantioselectivity issues. To overcome these limitations, a new mechanism is needed to control both of these simultaneously. Herein, we report the first Pd catalyzed regioselective distal and atroposelective olefination of simple arenes/biaryls via an electrooxidative reaction pathway. This unique electro-oxidative strategy with Pd(II) catalysis demonstrates unprecedented access to 'regio-resolved' reactions, furnishing chiral molecule synthesis under dynamic kinetic resolution without the conventional requirement of metal-based oxidants and thermal energy. Both electroanalytical studies and DFT calculations suggest the involvement of a Pd(II)/Pd(IV) catalytic cycle via a crucial Pd(III) intermediate that initiates both the distal and atroposelective olefination reactions.

Toxicity remains one of the major challenges that prevent Pb-based halide perovskites from widespread utilization. Ideally, non-toxic alternatives can be identified while still maintaining the superior power conversion efficiency of the Pb-based perovskite solar cells. Using the currently most promising candidate, the Sn-based halide perovskites, as an example, we show that a trade-off exists between toxicity and efficiency in the Sn- versus Pb-based halide perovskites. Indeed, the dominant nonradiative recombination center in the Sn-based halide perovskites differs from the one in its Pb-based counterparts, resulting in the nonradiative capture coefficient in CsSnI3 being an order of magnitude higher than that in CsPbI3. We attribute this difference to the band alignment. Our results indicate that development of halide perovskites beyond the Pb and Sn bases is essential for efficient yet environmentally friendly perovskite solar cells.