Unique (3,12)-Connected Porous Lanthanide−Organic Frameworks Based on Ln₄O₄ Clusters: Synthesis, Crystal Structures, Luminescence, and Magnetism

Abstract

Three porous lanthanide-organic frameworks, [Ln(4)(OH)(4)(3-SBA)(4)(H(2)O)(4)].nH(2)O [Ln = Eu(III) (1), n = 10; Gd(III) (2), n = 10; Tb(III) (3), n = 8; 3-SBA = 3-sulfobenzoate], have been prepared by a hydrothermal synthesis method. They are isomorphous and crystallize in a tetragonal system with space group P 42(1)c. The structure can be considered to be built up by cubanelike [Ln(4)(OH)(4)](8+) secondary building units, which are further connected by 3-SBA to form a 3D coordination framework with 1D pores along the c direction for accommodation of novel T8(3) water tapes or zigzag water chains. Furthermore, in these compounds, the [Ln(4)(OH)(4)](8+) units and 3-SBA ligands serve as 12-connected and 3-connected nodes, respectively, resulting in a unique (3,12)-connected framework with the Schlafli symbol of (4(3))(4)(4(20).6(28).8(18)). The luminescent properties of the Eu(III) (1) and Tb(III) (3) complexes have been studied, showing characteristic emissions at room temperature. Variable-temperature magnetic susceptibility studies indicate that the Gd(III) complex 2 displays weak antiferromagnetic coupling through mu(3)-OH(-) pathways.