Chiral hybrid organic-inorganic metal halides (HOIMHs) with noncentrosymmetric structure have attracted significant attention for nonlinear optics (NLO). Herein, guided by atom response theory (ART), we screened representative lead-free metal halide polyhedra and found that NbCl6- exhibits the highest linear polarizability. Therefore, we constructed the first chiral niobium-based HOIMHs, (R/S-3BrMBA)NbCl6 (R/S-Nb), and investigated their NLO properties. As expected, S-Nb exhibits efficient second harmonic generation (SHG) under 770-1000 nm excitation. Most importantly, the effective second-order NLO coefficient (deff) of S-Nb reaches 6.77 pm/V, representing the highest value among the reported zero-dimensional chiral HOIMHs. Moreover, S-Nb demonstrates strong SHG circular dichroism (SHG-CD) under circularly polarized excitation, with an anisotropy factor (gSHG-CD) of 1.37, which is one of the highest values among chiral HOIMHs. Our results highlight the potential of chiral niobium halides toward nonlinear chiroptical applications and provide an effective ART-guided strategy for designing high-performance NLO material through polarizability and band-gap engineering.
Liu et al. (Fri,) studied this question.