A family of 3D lanthanide oxalatosuccinate with rare structures: 3D host framework incorporating a 3D alkali metal guest lattice

A family of 3D metal–organic frameworks Na2Ln2(ox)3(suc)·(H2O)2, (Ln = Nd 1, Eu 2, Gd 3, Tb 4, ox = oxalate, suc = succinate) have been hydrothermally synthesized by self-assembly of succinic, sodium oxalate and Ln3+. They were characterized by X-ray crystallography, revealing that they crystallize in monoclinic groupP21/c. Ln3+ cations adopt a 9-fold configuration. Ox ligands play a unique dual role. These salts bear extraordinary structural features which result from host–guest interactions. Ln3+ cations, ox anions and succinate anions construct a host 3D framework. Guest Na+ cations are connected by ox ligands to construct a 3D alkali metal guest lattice, which is incorporated in the host 3D framework. Na+ cations adopt a fairly rare 7-fold configuration. The host–guest interaction would be more evident when sodium oxalate is displaced by oxalic acid, leading to an open framework [Nd2(ox)(suc)2·(H2O)4]·4H2O (5), where Nd3+ cations are 8-fold. Complex 5 bears a layer-pillared 3D structure, orthorhombic groupFddd, distinct from that of complex 1. Their thermal behavior, luminescence properties, and magnetic properties have been studied.