Sn<sup>4+</sup> Alloying and Chiral Incorporation\ninto Tellurium Halides Triggering Tunable Luminescence Emission and\nSecond-Harmonic Generation

Recently,\nchiral organic–inorganic hybrid metal halides\nhave attracted considerable interest as promising multifunctional\nmaterials, benefiting from their diverse structures and tunable photophysical\nproperties. Herein, by introducing the chiral ligand methylbenzylamine\n(<i>R</i>-/<i>S</i>-MBA) and alloying Sn<sup>4+</sup> cation, a series of tellurium-based halides <i>R</i>-/<i>S</i><b>-MBA</b><sub><b>2</b></sub><b>Sn</b><sub><b><i>x</i></b></sub><b>Te</b><sub><b>1</b>–<i>x</i></sub><b>Cl</b><sub><b>6</b></sub> (<i>x</i> = 0, 0.125, 0.2, 0.365 and 0.54)\nwith second-harmonic generation (SHG) effect and photoluminescence\n(PL) properties are successfully synthesized. Their optical bandgaps\nare determined to be 2.48–2.6 eV. Specifically, the introduction\nof chiral organic cations could break the structural symmetry and\ncause the tellurium halide to crystallize in the chiral space group.\nThe incorporation of isovalent Sn<sup>4+</sup> into the chiral host\ntellurium halides results in the increase in octahedral distortion,\nthereby promoting host intrinsic self-trapped emission that originates\nfrom the interconfigurational <sup>3</sup>P<sub>0,1</sub> → <sup>1</sup>S<sub>0</sub> transitions of Te<sup>4+</sup>. Consequently,\nthe as-prepared Sn<sup>4+</sup> doped halides, <i>R</i>-/<i>S</i>-MBA<sub>2</sub>Sn<sub><i>x</i></sub>Te<sub>1–<i>x</i></sub>Cl<sub>6</sub> (<i>x</i> = 0.365, 0.54),\nexhibit not only SHG response but also bright orange fluorescence.\nThis study provides an effective strategy for designing chiral multifunctional\nmaterials.