Chiral Hybrid Germanium(II) Halide with Strong Nonlinear Chiroptical Properties

Abstract Due to the pronounced anisotropic response to circularly polarized light, chiral hybrid organic–inorganic metal halides have been regarded as promising candidates for the application in nonlinear chiroptics, especially for the second‐harmonic generation circular dichroism (SHG‐CD) effect. However, designing novel lead‐free chiral hybrid metal halides with large anisotropy factors and high laser‐induced damage thresholds (LDT) of SHG‐CD remains challenging. Herein, we develop the first chiral hybrid germanium halide, ( R / S ‐NEA) 3 Ge 2 I 7 ⋅H 2 O ( R / S ‐NGI), and systematically investigated its linear and nonlinear chiroptical properties. S ‐NGI and R ‐NGI exhibit large anisotropy factors ( g SHG‐CD ) of 0.45 and 0.48, respectively, along with a high LDT of 38.46 GW/cm 2 ; these anisotropy factors were the highest values among the reported lead‐free chiral hybrid metal halides. Moreover, the effective second‐order nonlinear optical coefficient of S ‐NGI could reach up to 0.86 pm/V, which was 2.9 times higher than that of commercial Y‐cut quartz. Our findings facilitate a new avenue toward lead‐free chiral hybrid metal halides, and their implementation in nonlinear chiroptical applications.