Hybrid perovskite semiconductor materials are predicted to lock chirality into place and encode asymmetry into their electronic states, while softness of their crystal lattice accommodates lattice strain to maintain high crystal quality with low defect densities, necessary for high luminescence yields. We report photoluminescence quantum efficiencies as high as 39% and degrees of circularly polarized photoluminescence of up to 52%, at room temperature, in the chiral layered hybrid lead-halide perovskites (R/S/Rac)-3BrMBA2PbI4 [3BrMBA = 1-(3-bromphenyl)-ethylamine]. Using transient chiroptical spectroscopy, we explain the excellent photoluminescence yields from suppression of nonradiative loss channels and high rates of radiative recombination. We further find that photoexcitations show polarization lifetimes that exceed the time scales of radiative decays, which rationalize the high degrees of polarized luminescence. Our findings pave the way toward high-performance solution-processed photonic systems for chiroptical applications and chiral-spintronic logic at room temperature.

A series of rare earth complexes of the form Ln(L^R)₃ supported by bidentate ortho-aryloxide-NHC ligands are reported (L^R = 2-O-3,5-^tBu₂-C₆H₂(1-C{N(CH)₂N(R)})); R = ⁱPr, ^tBu, Mes; Ln = Ce, Sm, Eu). The cerium complexes cleanly and quantitatively insert carbon dioxide exclusively into all three cerium carbene bonds, forming Ce(L^R·CO₂)₃. The insertion is reversible only for the mesityl-substituted complex Ce(L^Mes)₃. Analysis of the capacity of Ce(L^R)₃ to insert a range of heteroallenes that are isoelectronic with CO₂ reveals the solvent and ligand size dependence of the selectivity. This is important because only the complexes capable of reversible CO₂-insertion are competent catalysts for catalytic conversions of CO₂. Preliminary studies show that only Ce(L^Mes·CO₂)₃ catalyses the formation of propylene carbonate from propylene oxide under 1 atm of CO₂ pressure. The mono-ligand complexes can be isolated from reactions using LiCe(NⁱPr₂)₄ as a starting material; LiBr adducts [Ce(L^R)(NⁱPr₂)Br·LiBr(THF)]₂ (R = Me, ⁱPr) are reported, along with a hexanuclear N-heterocyclic dicarbene [Li₂Ce₃(OArC^Me-H)₃(NⁱPr₂)₅(THF)₂]₂ by-product. The analogous para-aryloxide-NHC proligand (p-L^Mes = 4-O-2,6-^tBu₂-C₆H₂(1-C{N(CH)₂NMes}))) has been made for comparison, but the rare earth tris-ligand complexes Ln(p-L^Mes)₃(THF)₂ (Ln = Y, Ce) are too reactive for straightforward Lewis pair separated chemistry to be usefully carried out.