[C5H12N]SnCl3: A Tin Halide Organic–Inorganic Hybrid as an Above-Room-Temperature Solid-State Nonlinear Optical Switch

Nonlinear optical (NLO) switches driven by a solid-state structural phase transition have attracted extensive attention; however, above-room-temperature solid-state NLO switch materials are still sparse. Herein, we report an above-room-temperature tin halide organic–inorganic hybrid quadratic NLO switchable material, N-methylpyrrolidinium trichloride stannite (C₅H₁₂N]SnCl₃, MPSC). The MPSC crystal exhibits a phase-matchable NLO property that is 1.1 times that of KH₂PO₄ (KDP) and NLO switching behavior, changing from a high second harmonic generation (SHG) response to a low SHG response at 383 K, thereby demonstrating its prospective applications in the field of nonlinear optics. Variable-temperature crystal structural analysis combined with theoretical calculations revealed that the large NLO response stems from the inorganic SnCl₃ moiety, whereas the high-performance NLO switching properties mainly originate from the order/disorder transformation of the N-methylpyrrolidinium. This work provides a new approach to designing and exploring new high-performance quadratic NLO switches involving tin halide organic–inorganic hybrids.