Lithium Melonate, Li-3[C6N7(NCN)(3)]center dot 6H(2)O - Synthesis, Crystal Structure and Thermal Properties of a Novel Precursor for Graphitic Carbon Nitrides

摘要

A new s-heptazine derivative, lithium melonate Li-3[C6N7(NCN)(3)] (2), has been prepared from potassium melonate by using an ion exchanger resin. The crystal structure of the hexahydrate Li-3[C6N7(NCN)(3)]center dot 6H(2)O (2a) has been determined by X-ray diffraction analysis (hexagonal, P6(3)/m, a = b = 12.2263(6), c = 6.8854(6) angstrom, V = 891.35(10) angstrom(3)) The results show that this s-heptazine derivative adopts ideal C-3h symmetry, thus comprising 1/6 of the formula moiety in the asymmetric unit. C-13 NMR spectroscopic data indicate that no melonate-lithium interaction occurs in solution, whereas lithium is tetrahedrally coordinated by two oxygen and two nitrogen atoms in 2a in the solid. The title compound 2 was further characterised by FTIR Raman spectroscopy, TG/DTA and elemental analysis. In spite of the high nitrogen content, compound 2 proved to be thermally stable up to similar to 500 degrees C. The latter observation is typical for melonates and has been reported for other s-heptazine derivatives as well.