Halogen regulation triggers NLO and dielectric dual switches in hybrid compounds with green fluorescence

Hybrid metal halides with nonlinear optical (NLO) and dielectric dual switching properties are a class of materials with great application prospects in the fields of optoelectronics and smart devices. However, effectively modifying and regulating molecular structures to obtain temperature-responsive NLO switching performance is still a challenge. Herein, we reported a strategy to modify symmetry by employing halogen substitution. Br with greater electronegativity reduced the symmetry from the centrosymmetric (Cl-MM)2MnBr4 (1) to the noncentrosymmetric (Br-MM)2MnBr4 (2). Therefore, the structure was enriched with NLO, and its NLO can be switched by the structural phase transition. Then it is natural that the reversible dielectric switches were triggered in both the lead-free compounds by the phase changes. In addition, they exhibit bright green fluorescence under ultraviolet light, and the photoluminescence quantum efficiency reaches 47.24% and 40.69%, respectively. These results indicate that the halogen-modification strategy has injected new vitality into the exploration of the development of multi-response materials with NLO and dielectric switching performance.