Crystal Growth, Structural and Thermal Studies of FeC4H4O6·2.5H2O

Single crystals of iron(II) tartrate hemi-pentahydrate, FeC4H4O6·2.5H2O, were grown by the gel method using silica gels. Differential scanning calorimetry, thermogravimetric-differential thermal analysis, and X-ray diffraction measurements were performed on the single crystals. The space group symmetry (orthorhombic P212121) and structural parameters were determined at room temperature. The crystal structure consisted of slightly distorted FeO6 octahedra, C4H4O6 and H2O molecules, C4H4O6-Fe-C4H4O6 chains jointed by Fe-O bonds, and O-H···O hydrogen-bonding frameworks between adjacent molecules. Weight losses due to thermal decomposition of the crystal were found to occur in the temperature range of 300-1060 K. We inferred that the weight losses were caused by the evaporation of bound water molecules and the evolution of H2CO, CO, and O2 gases from C4H4O6 molecules, and that the black residue after decomposition was composed of triiron tetraoxide (Fe3O4) and carbon.