Stabilization of caesium ions by simple organic molecules: crystal structures of Cs(OXL) (OXL = oxalurate anion) and the CsOH/cyanuric acid co-crystal Cs3(CYH3)4(OH)3 (CYH3 = cyanuric acid)

Abstract

The reaction in water between CsOH and parabanic acid (PBH₂) leads to the formation of the caesium salt of the oxalurate anion Cs(OXL), while the reaction with cyanuric acid (CYH₃) leads to the formation of the CsOH co-crystal of cyanuric acid Cs₃(CYH₃)₄(OH)₃. The X-ray crystal structures of these compounds show that both the organic moieties OXL and CYH₃ form robust homomeric ribbons based on strong and articulated N–H⋯O hydrogen bonds. The stabilization of the Cs⁺ ions can occur regardless of whether the ribbon of organic units is negatively charged or neutral. In Cs(OXL), each cation displays nine-fold coordination with Cs–O distances in the range of 2.975(3)–3.601(4) Å; in Cs₃(CYH₃)₄(OH)₃, two of the Cs⁺ cations (Cs1 and Cs2) display a nine-fold coordination with Cs–O distances in the range of 3.007(9)–3.823(13) Å and one (Cs3) is ten-fold coordinated with Cs–O distances in the range of 3.161(14)–3.653(17) Å. The molecular electrostatic potential maps of OXL and di-OXL anions have been reported and discussed.