Topological aspects of lanthanide-adipate-aqua compounds: Close packed and open framework structures

摘要

A search in the Cambridge Structural Database (CSD) for lanthanide complexes with adipate [OOC(CH_2)_4 COO]~(2-) and aqua ligands retrieved a fair number of compounds. To this dataset a new lanthanum metalorganic framework, {[La_2(adip)_3(H _2O)_2] (1) (adipH_2 = adipic acid), synthesised and structurally characterized in these labs, was included. The crystal structures of these coordination polymers, of general formulation [Ln _2(adip)_3(H_2O)_x], exhibit a variety of topologies and dimensionality, which were clustered in different classes and described in detail. It was explored that the majority of these evidences the presence of metal chains or dinuclear Ln_2 entities (separated in both cases by 4.0-4.8 ?), where lanthanide ions are differently connected by carboxylate groups with chelating or oxygen-bridging mode. The different amount of coordinated water molecules appear to affect the solid state networks. Moreover the crystal packing of these compounds shows peculiar aspects and examples were reported in the literature where the long alkyl chain of adipate connectors give rise to interpenetrated structures, or to porous material where lattice water or neutral larger molecules are clathrated.