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Often, the quasi-spherical molecule 1,4-diazabicyclo[2.2.2]octane (2.2.2-dabco) is chosen to prepare switchable materials with a high phase transition temperature. We wished to reduce molecular symmetry but maintain a quasi-spherical shape. Hence, a similar molecule, 1,4-diazabicyclo[3.2.2]nonane (3.2.2-dabcn), was used to react with equimolar amounts of HClO4 or HReO4 in aqueous solution. Two compounds [3.2.2-Hdabcn]X (X = ClO4, 1; ReO4, 2) with high phase-transition points at 418 K for 1 and 394.6 K and 419.2 K for 2, respectively, were isolated, in which one-dimensional cationic chains were connected by different types of hydrogen bonds. Differential scanning calorimetry and dielectric-permittivity measurements revealed that 1 and 2 showed switchable phase transition and dielectric anomalies. Compound 1 also showed a reversible second-harmonic-generation effect. [ABSTRACT FROM AUTHOR]

Switchable second harmonic generation (SHG) materials have potential applications in information storage, signal processing, and so on because they can switch between SHG-on and SHG-off states. In this work, we designed and synthesized three organic-inorganic hybrid Rb halide three-dimensional (3D) perovskite materials [1 S ,4 S 2,5-2.2.1-H 2 dabch]RbX 3 ·0.5H 2 O (X = Cl, 1 ; Br, 2 ; I, 3 ) based on the chiral 1 S ,4 S -2,5-diazabicyclo[2.2.1]heptane (1 S ,4 S -2,5-2.2.1-dabch). The selection of homochiral organic cations ensures that the compounds 1 ∼ 3 crystallize in the noncentrosymmetric and chiral space group P 2 1 2 1 2 1 , which further leads to reversible SHG responses of the three compounds. Through differential scanning calorimetry (DSC) and dielectric measurements, it revealed that the phase transition point of the compounds 1 ∼ 3 increased with RbCl, RbBr, and RbI. This is because the hydrogen interaction H···X between the inorganic framework [RbX 3 ] n and the organic cation [1 S ,4 S -2,5-2.2.1-H 2 dabch] 2+ is increased with the order of I > Br > Cl. This study can provide an effective molecular design strategy for the exploration and construction of temperature-tunable SHG switching materials.