The first example of tetranuclear lanthanide complexes with 2-sulfobenzoate and 1,10-phenanthroline

Four novel complexes {[Ln2(2-SB)3(phen)3(H2O)2] · nH2O}2 (Ln = Sm (1), n = 3; Ln = Eu (2), n = 2; Ln = Tb (3), n = 2; and Ln = Dy (4), n = 2.5; 2-SB = 2-sulfobenzoate, phen = 1,10-phenanthroline), were synthesized by hydrothermal reactions and characterized using single-crystal X-ray diffraction, thermogravimetric analyses and luminescence spectroscopy. In the four complexes, there are two types of Ln(III) ion coordination environments. Ln(III) ions are connected together through 2-SB ligands via μ2-, η3- and η2-coordination modes, resulting in a tetranuclear molecule with central symmetry, indicating novel structural features. The emission spectra of the four complexes indicate the typical luminescence characteristics of the Sm(III) for 1, Eu(III) for 2, Tb(III) for 3, and Dy(III) ions for 4, respectively.