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

Abstract

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.