Hg3O2(NO3)F: a mercury nitrate oxyfluoride with an unprecedented [(Hg3O2F)+]∞ cationic framework and excellent optical anisotropy

Abstract

Combining multiple anions to design compounds with novel structures and excellent optical properties has become a hot research field. In this paper, a novel nitrate oxyfluoride, Hg₃O₂(NO₃)F, has been obtained. Hg₃O₂(NO₃)F features an unprecedented [(Hg₃O₂F)⁺]_∞ cationic framework constructed by V-shaped HgO₂ units and original HgO₂F₂ tetrahedra and with isolated NO₃⁻ anions balancing the charge. Hg₃O₂(NO₃)F is the first nitrate oxyfluoride containing a d¹⁰ metal. Importantly, Hg₃O₂(NO₃)F exhibits superior optical anisotropy with the calculated birefringence of Δn = 0.23 at 1064 nm. Based on the theoretical calculation analyses, the good optical anisotropy is mainly derived from the well-arranged V-shaped HgO₂ units. This work proves that the strategy of introducing heteranions is effective for exploring high-performance optical materials.