Synthesis and Structure of the Calcium Complex with Meconic Acid

Abstract

The structure and composition of the calcium complex with meconic acid (5-hydroxy-4-oxo-4H-pyran-2,6-dicarboxylic acid), calcium meconate, were studied. Elemental analysis and X-ray diffraction analysis determined the composition of the complex compound [Ca(H2Mec)2(H2O)4]·4H2O. The compound crystallizes in the monoclinic space group P21/n as an octahydrate, with four water molecules in the first coordination sphere of the calcium cation and four additional water molecules forming the outer coordination sphere through hydrogen bonds. The formation of coordination bonds between the meconic acid residue and the calcium cation in the complex was also confirmed by indirect methods (NMR and IR spectroscopy). Quantum chemical calculations were used to correlate the experimental and calculated vibrational frequencies in the IR spectrum of calcium meconate.