Alkali Ion – Ce < sup > 3+ < /sup > – DipicH < inf > 2 < /inf > System : Coordination Networks and Water Clusters.

Abstract

Heterometallic coordination polymers having the general formula [A3(H2O)nCe(dipic)3]⋅mH2O, where A denotes an alkali metal ion (Li–Cs), have been obtained by reacting an aqueous solution of Ce(NO3)3⋅6H2O with alkali hydroxides in presence of dipicH2. Ce(dipic)33– ion functions as a metallo-ligand by linking the alkali ions. While the lightest alkali ion forms a 2D coordination network (1, n=6, m=3), all others form 3D networks (Na: 2, n=8, m=7; K: 3, n=9, m=3; Rb: 4 and 5, n=6, m=2; Cs: 6, n=6, m=3). The structure of compound 2 was inferred from the isomorphous Na−Gd compound (7) which formed better quality crystals. Remarkably, both Na and K networks are built around alkali ion-water chains. In the case of the three lighter alkali ions, the lattice water molecules are assembled into water clusters: tetramer (Li); acyclic heptamer (Na); water tape (K). X-ray powder diffraction studies show that the hydrated structures could be regenerated by exposure of the dehydrated samples to moisture in the case of Li, Na and K, but not for Rb and Cs.