Exceptional Optical Anisotropy Enhancement Achieved Through Dual-Ions Cosubstitution Strategy in Novel Hybrid Bismuth Halides

초록

Guided by a superb dual-ions cosubstitution strategy, two novel, highly optically anisotropic hybrid bismuth halides are designed and synthesized. The first compound, Gu3Bi2NO3Cl8 (Gu = C(NH2)3), is developed using the 2D perovskite halide Cs3Bi2Cl9 as the maternal structure. This involved substituting all Cs+ cations with organic Gu+ and replacing some Cl- anions with [NO3]-. Further substitution of Cl- with additional [NO3]- resulted in the formation of nitrate-rich Gu2Bi(NO3)3Cl2 crystal, exhibiting a 3.4-fold increase in [NO3]- per unit volume. Both compounds have a structurally 0D nature, comprising bismuth-centered polyhedra formed by coordinated chlorides and monodentate/bidentate nitrate moieties, with Gu+ serving as a separator and linker. Notably, the presence of superb optically anisotropic dual-ions, i.e., planar Gu+ and [NO3]-, enables these crystals to possess sharply enhanced optical anisotropy, with birefringence values more than 1 order of magnitude higher than that of the initial crystal Cs3Bi2Cl9 (0.162/0.186vs 0.011 at 546 nm). The discovery and characterization of Gu3Bi2NO3Cl8 and Gu2Bi(NO3)3Cl2 crystals provide new insights into achieving expected modifications in optical properties through the utilization of a dual-ions cosubstitution strategy. In this study, two optically anisotropic hybrid bismuth halides, Gu3Bi2NO3Cl8 and Gu2Bi(NO3)3Cl2, are designed and synthesized using a dual-ions cosubstitution strategy based on the known Cs3Bi2Cl9. Notably, the incorporation of superior anisotropic Gu+ and [NO3]- in these two crystals resulted in remarkably enhanced birefringence, surpassing the values of the initial Cs3Bi2Cl9 crystal by more than 1 order of magnitude.image

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