Novel Alkali Triazine Tricarboxylates Li3[C3N3(CO2)3]•4H2O, Rb3[C3N3(CO2)3]•2H2O and Cs3[C3N3(CO2)3]•2H2O-Synthesis, Crystal Structure and Thermal Behavior

The alkali 1,3,5-triazine-2,4,6-tricarboxylates Li3[C3N3(CO2)3]center dot 4H2O, Rb3[C3N3(CO2)3]center dot 2H2O and Cs3[C3N3(CO2)3]center dot 2H2O were synthesized by saponification of the respective triethyl ester in aqueous solution. In the crystal structure, the triazine tricarboxylate (TTC) units and metal ions are arranged in layers alternating with layers of crystal water molecules. Within the layers the triazine tricarboxylate entities form either strands in Li3[C3N3(CO2)3]center dot 4H2O or a hexagonal arrangement in Rb3[C3N3(CO2)3]center dot 2H2O and Cs3[C3N3(CO2)3]center dot 2H2O. Perpendicular to the layers, the triazine cores exhibit varying degrees of pp stacking dependent on the metal ions resulting in the formation of rods in Rb3[C3N3(CO2)3]center dot 2H2O and Cs3[C3N3(CO2)3]center dot 2H2O. Additionally, the thermal behavior of the alkali triazine tricarboxylates was investigated by means of FT-IR spectroscopy, TG and DTA measurements. Differences and similarities regarding structural features and thermal behavior are discussed for the obtained novel alkali triazine tricarboxylates and potassium triazine tricarboxylate dihydrate.