Vibrational and Thermal Evidence of Coordinated Water and Carboxylate Groups in Crystalline Calcium Malonate Dihydrate

• Published in: Journal of solid state chemistry Vol. 143; no. 2; pp. 174 - 181
• Main Authors: Brusau, E.V., Narda, G.E., Pedregosa, J.C., Echeverria, G., Punte, G.M.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.03.1999; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Infrared and raman spectra and scattering; Inorganic compounds; Miscellaneous; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other nonmetallic inorganics; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Raman spectra; Inorganic compounds; Calcium compounds; XRD; Infrared spectra; Lattice vibrations; Dehydration; Experimental study; Thermal properties; Organic anion; Vibrational modes; Organic salt; Carboxylates; Hydrates; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1999.8069

Revision of the crystal structure of calcium malonate dihydrate, [Ca(mal)(H2O)2], has shown that it belongs to the monoclinic system, space groupC2/m, witha=13.857(6),b=6.8072(8),c=6.806(5) Å,β=106.31(7)°,Z=4, andV=616.2(5) Å3. This is in agreement with one of the previous structural determinations, and nonequivalent water molecules and chelating and bridging carboxylate groups in the crystal lattice are evidenced. The infrared and Raman spectra were recorded and discussed in relation to the structural properties. Librational modes of water have been clearly identified and an assignment for all the internal modes is proposed. The thermal dehydration and decomposition processes were investigated using TG/DTA measurements. The structural model is consistent with the vibrational behavior and the two different temperatures observed in the dehydration process.