Lanthanide(III) Complexes with Thiodiacetato Ligand: Chemical Speciation, Synthesis, Crystal Structure, and Solid-State Luminescence

The synthesis, crystal structures, and luminescence of two lanthanide polynuclear complexes with the general formula [Ln2(tda)3(H2O)5]·3H2O (Ln = Sm, Eu; tda = thiodiacetato anion) are reported. The compounds were obtained by direct reaction of H2tda and lanthanide(III) chloride in an aqueous solution. The choice of the conditions of synthesis was based on speciation studies. The structure of the polymeric complexes contains Ln(III) ions in a tricapped trigonal prism geometry. The versatility of this ligand provides different coordination modes and provokes the formation of thick 2D sheets. Direct excitation of the Ln(III) ions gives place to the characteristic intra-configuration sharp luminescence emission of both complexes in the solid state.