Vibrational and thermal evidence of coordinated water and carboxylate groups in crystalline calcium malonate dihydrate

Revision of the crystal structure of calcium malonate dihydrate, [Ca(mal)(H 2O)(2)], has shown that it belongs to the monoclinic system, space group C2 /m, with a 13.857(6), b = 6.8072(8), 6.806(5) Angstrom, beta = 106.31(7)deg rees, Z = 4, and V = 616.2(5) Angstrom(3). 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 ev idenced, The infrared and Raman spectra were recorded and discussed in rela tion to the structural properties, Librational modes of,vater have been cle arly identified and an assignment for all the internal modes is proposed, T he thermal dehydration and decomposition processes were investigated using TG/DTA measurements, The structural model is consistent with the vibrationa l behavior and the two different temperatures observed in the dehydration p rocess, (C) 1999 Academic Press.