Low-dimensional hybrid perovskites have demonstrated excellent performance as white-light emitters. The broadband white emission originates from self-trapped excitons (STEs). Since the mechanism of STEs formation in perovskites is still not clear, preparing new low-dimensional white perovskites relies mostly on screening lots of intercalated organic molecules rather than rational design. Here, we report an atom-substituting strategy to trigger STEs formation in layered perovskites. Halogen-substituted phenyl molecules are applied to synthesize perovskite crystals. The halogen-substituents will withdraw electrons from the branched chain (-R-NH3+) of the phenyl molecule. This will result in positive charge accumulation on -R-NH3+, and thus stronger Coulomb force of bond (-R-NH3+)-(PbBr42−), which facilitates excitons self-trapping. Our designed white perovskites exhibit photoluminescence quantum yield of 32%, color-rendering index of near 90 and chromaticity coordinates close to standard white-light. Our joint experiment-theory study provides insights into the STEs formation in perovskites and will benefit tailoring white perovskites with boosting performance.

Dearomatization of anthranils with vinylcyclopropanes (VCPs) by Pd-catalyzed [4+ +3] cyclization reaction has been realized.Inthe presence of acatalytic amount of borane as an activator,bridged cyclic products were obtained in good to excellent yields with excellent stereoselectivities.B yi ntroducing ac hiral PHOXl igand (L5), asymmetric dearomatization reactions of anthranils with vinylcyclopropanes proceeded with excellent enantioselectivity.Borane playsakey role for the reactivity,likely owing to the formation of aborane-anthranil complex which has been confirmed by NMR experiments. Scheme 3. Asymmetric dearomative [4+ +3] cyclization reactions.Scheme 4. Transformations of product 3aa.

An efficient strategy which integrates visible-light-induced iminyl-radical formation with carboimination of unactivated alkenes has been developed for the easy access of densely functionalized pyrroline derivatives. With fac-[Ir­(ppy)3] as photoredox catalyst, the acyl oximes were converted into iminyl radical intermediates by one electron reduction, and evolve through a cascade of intramolecular cyclization and intermolecular carbon radical trapping to give the functionalized pyrrolines. The utilization of silyl enol ethers as coupling partners not only allows the introduction of synthetically useful ketone functionalities but also renders catalyst regeneration without any external reductants. This protocol is characterized by its mild reaction conditions and the tolerance of a broad range of functionalities.