Chiral Molecules Induce Enantiomorphic Lattice Helicity in Chiral 0D Tin Bromide Crystals

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Abstract
Chiral organic–inorganic hybrid metal halides have emerged as a promising class of materials for spin‐controlled optical and optoelectronic effects and related applications. Chiral hybrid metal halides generally crystallize in non‐helical space groups. Herein, we report the discovery of zero‐dimensional (0D) chiral (R/S‐MBA)2SnBr6 (MBA: methylbenzylammonium cation) single crystals with enantiomorphic lattice helicity. The S‐enantiomer of the chiral molecule induces right‐handed helicity with the P61 space group (right‐handed, P‐helix), while the R‐enantiomer induces right‐handed helicity with the P65 space group (left‐handed, M‐helix). The chiral molecules induce the helical twist of inorganic units in the lattice through N─H···Br and C─H···π interactions. Density functional theory (DFT) calculations indicate that the strong electronic coupling between chiral molecules and SnBr62− subunits is responsible for the generation of chirality. The chiral crystals exhibit circular dicroism (CD) spectra with a high dissymmetry factor (gCD) of 3.5 × 10−2 and no Cotton effect, maintaining the same CD sign throughout the spectrum. In addition, they exhibit broadband second harmonic generation (SHG) over a broad excitation range, with a gCP‐SHG up to 0.44. Furthermore, we find that the alloying of Sn with Pb leads to a change in dimensionality from 0D to non‐helical 1D structures. These crystals with helical lattices and interesting CD responses are expected to open new avenues for spin‐controlled applications.
Funding Information
  • Agencia Estatal de Investigación (TED2021‐131628A‐I00, CNS2022‐135531, PID2023‐147567NB‐I00, MICIU/AEI/10.13039/501100011033)
  • Deutsche Forschungsgemeinschaft (EXC 2089/1 – 390776260, FKZ 05D23WO1)
  • Ministerio de Ciencia, Innovación y Universidades (PID2022‐138023NB‐I00)

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