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Crystal Engineering of Complexes of Propane-1,2,3-tricarboxylic Acid (H3tca) with Lanthanide(III) Cations

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posted on 02.04.2008, 00:00 by Laura Cañadillas-Delgado, Oscar Fabelo, Jorge Pasán, Fernando S. Delgado, Maríadel Déniz, Eliezer Sepúlveda, María-Milagros Laz, Miguel Julve, Catalina Ruiz-Pérez
The knowledge of the one-synthon based supramolecular network of the propane-1,2,3-tricarboxylic acid (H3tca), commonly referred to as tricarballylic acid (1), induced us to look for new architectures of tricarballylate-containing lanthanide(III) cations having in mind that the structure of the complex [Ce(tca)(H2O)2]n is the only reported example of this type of compounds. Three novel complexes of formulas [Gd(tca)(H2O)3]n·nH2O (2), [Eu(tca)(H2O)3]n·nH2O (3), and [La2(tca)2(H2O)5]n·4nH2O (4) have been synthesized, and their structures have been determined by X-ray diffraction on single crystals. 2 and 3 are isomorphous compounds. They exhibit a layered structure where the lanthanide atoms are nine-coordinated with three water molecules and six carboxylate-oxygen atoms building a monocapped square antiprism surrounding and the tca ligands adopting a tris-bidentate coordination mode. 4 has a three-dimensional structure where two 10-coordinated, crystallographically independent lanthanum atoms [La(1) and La(2)] occur with three/two [La(1)/La(2)] water molecules and seven/eight [La(1)/La(2)] carboxylate-oxygens describing bicapped square antiprism surroundings. Two different tca groups are present in 4 both having in common the tris-bidentate coordination mode but acting in addition as monodentate and bis-monodentate ligands through one and two carboxylate groups, respectively.