Synthesis and crystal structure of the complex [Rb3(CYH2)3(CYH3)(H2O)4] (CYH3 = isocyanuric acid): An interesting case of disordered sub-structure, ordered super-structure

The reaction in water between RbOH and isocyanuric acid (CYH₃) leads, under mild reaction conditions (pH = 10, T = 20 °C), to the formation of crystals of good quality of the complex [Rb₃(CYH₂)₃(CYH₃)(H₂O)₄]. The ordered structure of [Rb₃(CYH₂)₃(CYH₃)(H₂O)₄] was refined from X-ray diffraction data, using a super-structure unit cell with a = 13.1315(1), b = 16.6198(1), c = 23.6865(1) Å, β = 99.751(1)°, and space group I2/a. The asymmetric unit of [Rb₃(CYH₂)₃(CYH₃)(H₂O)₄] contains three independent Rb⁺ cations, three CYH₂⁻ anions, one CYH₃ and four water molecules, all located in the unit cell in general position. The Rb⁺ cations with the water molecules are arranged to form layers intercalated by ribbons made by the CYH₂⁻ anions and CYH₃ molecules, in their keto-tautomeric form, that are coordinated to the cations through their oxygen atom, and interact each other and with the water molecules through hydrogen bonds. FT-IR and ATR-IR spectra of complex [Rb₃(CYH₂)₃(CYH₃)(H₂O)₄] are reported. Hirshfeld surface analysis (d_norm, shape index, curvedness) was also used to visualize the intermolecular interactions in the crystal structure. The low value of void percent in the crystal packing, to which the presence of water molecules contribute, indicates a compact crystal packing.