Two nonlinear optically responsive crown ether inclusion compounds based on a sulfonimide anion assembly

Organic amine crown ether supramolecular compounds, based on crystal engineering design, have already made significant research progress in functional devices such as ferroelectrics, ferroelastics and nonlinear optical materials, especially those involving anilinium cations, which have attracted widespread attention. In comparison, benzylammonium cations have been less studied and most counter-ions are inorganic metal salt anions, crystallizing in centrosymmetric space groups without nonlinear optical (NLO) response. By changing the anion, we have obtained two types of crown ether inclusion compounds, namely, benzylammonium bis(methanesulfonyl)azanide-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1), C₇H₁₀N⁺·C₂H₆NO₄S₂^-·C₁₂H₂₄O₆ or [(BA)(18-crown-6)][DMSA] [BA = benzylammonium and DMSA = bis(methanesulfonyl)azanide] and benzylammonium (methanesulfonyl)(trifluoromethylsulfonyl)azanide-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1), C₇H₁₀N⁺·C₂H₃F₃NO₄S₂^-·C₁₂H₂₄O₆ or [(BA)(18-crown-6)][TfNMs] [TfNMs = (methylsulfonyl)(trifluoromethylsulfonyl)azanide]. Both compounds crystallize in the polar chiral space group P2₁ at 100 K and exhibit a clear second harmonic generation (SHG) active characteristic, showing potential for use in quadratic nonlinear optical fields. Moreover, this work is the first to report crown-ether-based compounds using TfNMs as the counter-ion, enriching the choice of counter-anion for crown-ether-based compounds.