Perovskite-type organic–inorganic hybrid NLO switches tuned by guest cations

Abstract

Three organic–inorganic hybrid analogues, ([Et₃(n-Pr)P][Mn(dca)₃]) 1, ([Et₃(CH₂CHCH₂)P][Mn(dca)₃]) 2, ([Et₃(CH₂OCH₃)P][Mn(dca)₃]) 3, [dca = dicyanamide, N(CN)₂⁻], show similar three-dimensional perovskite frameworks, in which the guest phosphonium cations occupy the cavities. Compounds 1 and 3 belong to the orthorhombic noncentrosymmetric space group P2₁2₁2₁ at room temperature, while compound 2 crystallizes in the monoclinic centrosymmetric space group P2₁/c. Differential scanning calorimetry (DSC) and dielectric measurements confirmed the phase transitions in compounds 1, 2 and 3, where subtle structural distinctions of guest cations affect the crystal lattices, phase transition temperatures and physical properties. Interestingly, compounds 1 and 3 are SHG active at room temperature and can be used as NLO switches tuned by guest cations and triggered by temperature.