Enantiomorphic chiral structure in a 2D hybrid halide double perovskite: (R- and S-IdPA)4AgBiI8

Abstract

Chiral hybrid perovskites promise advanced chiral optoelectronic applications, relying on their structure–property correlation. A reasonable number of chiral hybrid perovskites have been already reported, but amongst them, only a few have higher order (more than 21) screw axes that are essential to form helical enantiomorphic space groups. For example, there is no report of double perovskites with helical enantiomorphic chiral structures. Here, we address the issue by synthesizing (R- and S-IdPA)4AgBiI8 (IdPA: 1-iodopropyl-2-ammonium) layered 2D hybrid double perovskites. (R- and S-IdPA)4AgBiI8 crystallize in the enantiomorphic chiral space group pair P41212 and P43212, with a fourth-order screw axis. Interestingly, gauche- and anti-conformers of IdPA cations are arranged alternately in the crystals. The two conformers have distinctly different noncovalent interactions with the inorganic layers, inducing structural asymmetry in the inorganic layers. In particular, the AgI6 unit gets hugely distorted, making the effective coordination number for Ag ∼ 2. The R- and S-enantiomers show mirror-image-like circular dichroism spectra originating from the electronic states of the inorganic sublattice. The films of (R- and S-IdPA)4AgBiI8 also show wavelength-tunable third-harmonic generation (THG) and, more importantly, THG circular dichroism (THG-CD) with a dissymmetry factor |gTHG-CD| of up to 0.13.