Two UV organic-inorganic hybrid antimony-based materials with superior optical performance derived from cation-anion synergetic interactions

Finding suitable strategies to effectively enhance the optical properties of materials are the goal being pursued by researchers. Herein, cation-anion synergetic interactions strategy was proposed to develop two novel organic-inorganic hybrid antimony-based optical materials, (C3H5N2)SbF2SO4 (I) and (C5H6N)SbF2SO4 (II), which were obtained by introducing Sb3+ cation containing stereochemically active lone-pair (SCALP) and organic π-conjugated cations into sulphate system. The synergistic interactions of the organic π-conjugated cations, the inorganic [SbO2F2]3− seesaw anions and the [SO4]2− distorted tetrahedra anions make their ultraviolet (UV) absorption edges approach 297 and 283 nm, respectively, and raise their birefringence up to 0.193@546 nm and 0.179@546 nm, respectively. Interestingly, although the two compounds have the same stoichiometric ratio and similar one-dimensional (1D) chain structure, they show opposite macroscopic symmetry, where the NCS compound (II) exhibits a large second-harmonic generation (SHG) response (1.6 times that of KH2PO4). The two reported compounds are found to be promising UV optical materials in the experimental tests.