The first coordination polymer of lanthanum(III) with a naphthalene-1,4,5,8-tetracarboxylic 1,8-anhydride derivative

The title compound, catena-poly[[[hepta-aqualanthanum(III)]- - 1,3-dioxo-2-oxa-1H,3H-phenalene-6,7-dicarboxyl-ato-² O ⁶:O ⁷] hemi(4,8-di-carboxy-naphthalene-1,5-dicarboxyl-ate) di-hydrate], {[La(C14H4O7)(H2O)7](C14H6O8)0.5·2H2O}n , is a dihydrate of a coordination polymer between the dianion of naphthalene-1,4,5,8-tetra-carboxylic 1,8-anhydride and the hepta-hydrated lanthanum(III) ion, charge balanced by an additional 4,8-dicarboxy-naphthalene-1,5-dicarboxyl-ate di-an-ion that is located on an inversion centre and is not coordinated to the metal ion. The linear polymeric arrays adopt a comb-like structure, and these pack in pairs with one chain inter-penetrating another, like two parts of a zip, to optimize stacking inter-actions between their ligand fragments. All the components of this compound are further inter-linked by an extensive pattern of O - H⋯O hydrogen bonds throughout the crystal structure. The main scientific significance of the results reported here is that they demonstrate for the first time the feasibility of coordination polymerization of the above organic ligand with lanthanide ions. The resulting polymer has a unique architecture. Finally, the reported structure is a rare example where the tetra-acid and the diacid anhydride ligand species co-exist in the same crystal.