Thermal behaviour of hydrated lanthanide complexes with heptanedioic acid

Abstract

The multi-step dehydration and decomposition of trivalent lanthanum and lanthanide heptanediate polyhydrates were investigated by means of thermal analysis completed with infrared study. Further more, X-ray diffraction data for investigated heptanediate complexes of general stoichiometry Lnz(CTHt004)3.nH20 (where n = 16 in the case of La, Ce, Pr, Nd and Sm pimelates, n = 8 for Eu, Gd, Tb, Dy, Er and Tm pimelates, n = 12 for Ho, Yb and Lu pimelates) were also reported.The last discoveries of new properties and oceurence of heptanedioie acid (usually called pimelic acid) and its compounds have indicated many possibilities of their practical use [1][2][3][4][5][6][7]. It is well known that heptanedioic acid durint heating undergoes a variety of transformations such as decarboxylation, eyclization and polymerization. Its complexes play a dominant role in biochemical systems and are used for preparation of some sorts of bactericides and antibiotic substances [8,9]. The salts of heptanedioic acid show the antidiabetic activity [10]. Pimelie acid inhibits the development of saprophytic mieroflora, and for that reason is used now for biological purification of wastewater from the production of synthetic fat [11].Heptanedioic acid as bidentate ligand forms easily eomplexes with a vide variety of metals; however only few data exist in literature on lanthanide pimelates. The preparation of these complexes and their solubility in water are published by Ryabehikov [12]