Guanidinium cyanurates versus guanidinium cyamelurates: Synthesis, spectroscopic investigation and structural characterization

Reactions of cyameluric acid and cyanuric acid with guanidine in water yield colorless crystals of two novel salts: triguanidinium cyamelurate hydrate [C(NH2)3]3·[C6N7O3]·3H2O (1) and guanidinium dihydrogencyanurate hydrate [C(NH2)3]2·[C3N3O3H2]2· H2O (2), respectively. The single crystal X-ray structures show that in the case of 2 there are two protons left at the triazine ring and two crystallographically independent cations and anions are present. In the case of triguanidinium cyamelurate 1, the heptazine ring is completely deprotonated with three crystallographically independent cations. Extensive networks of hydrogen bonds, involving all the molecular species, rule the crystal packing of both salts. Raman and FTIR spectra show the typical features expected for the heterocyclic anions and the guanidinium cation. Simultaneous thermal analysis (TG/DTA) indicates several decomposition steps resulting in 100% mass loss at ∼750 °C for 1 and ∼600 °C for 2.