Chiral Rare-Earth (Ce, Eu) Metal Halides with Bright\nCircularly Polarized Luminescence

Chiral\nmetal halide materials are emerging chiroptical materials\nthat are easy to synthesize and have a wide tunability. Rare-earth\n(RE) metals are desirable components to be incorporated in the hybrid\nregime; however, they are typically difficult to handle for solution-based\nhalide chemistry. Here, we report two new examples of chiral RE metal\nhalides with Ce(III) and Eu(III) with chiral alkanolammonium cations\n(<i>R</i>/<i>S</i>-3-hydroxyquinuclidium). These\ncompounds crystallize in the non-centrosymmetric space group <i>R</i>3, where their mirror-like symmetric circular dichroism\n(CD) and circularly polarized luminescence (CPL) further witness the\nchiral nature. The superior emission properties, including the high\nphotoluminescence quantum yield of the Ce-based materials (84–90%)\nand Eu-based materials (27–29%), have led to distinct and sharp\nsymmetrical CPL in the ultraviolet and visible regions, with dissymmetry\nfactors (<i>g</i><sub>lum</sub>) of ∼2 × 10<sup>–3</sup> and ∼4 × 10<sup>–3</sup>, respectively.\nThis work has established and expanded the materials space for chiral\nRE metal halides and demonstrated their potential for chiroptical\nand spintronic applications.