Luminescent Lanthanide Complexes with 1,2-Bis(ethylsulfinyl)ethane: Structural Dependences on Reacting Solvent, Ratio, and Co-Ligand

Abstract

The present paper reports our sequential efforts to investigate the structures and properties of flexible disulfoxide–lanthanide complexes. Combining our reported results, on the basis of changing synthesis conditions and using a co-ligand, six new complexes, [Ln(meso-L)4](ClO4)3(H2O) n (n = 0.5, Ln = Eu (1), Gd (2); n = 0, Ln = Tb (3)) and [Ln(meso-L)2(phen)2](ClO4)3(CHCl3)2 (Ln = Eu (4), Gd (5), and Tb (6)) (herein, L = 1,2-bis(ethylsulfinyl)ethane, phen = 1,10-phenanthroline) were synthesized, and their structures were characterized by IR spectroscopy, elemental analysis, and X-ray single-crystal diffraction. The dependence of the formation of 1–3 on the solvents used and reaction ratios in the preparation was confirmed. Complexes 1–3 are isomorphous ionic complexes, and the coordination cation is chiral and has a mononuclear structure, in which the LnIII atom is eight-coordinated by four L ligands. Complexes 4–6 are also isomorphous mononuclear ionic complexes, and in each complex cation, the central LnIII atom is eight-coordinated by two L ligands and two phen molecules. In 1–6, all the L ligands exhibit the meso configuration and bis-monodentate chelating coordination mode. Further, the absorption and luminescent spectra of L, phen and complexes 4–6 in solution were investigated at room temperature. The absorption spectra show that only a very slight shift of the absorption band occurred for the ligands L and phen when coordinating to metal ions, being consistent with their origin. The photoluminescence of 4 and 6 exhibits the usual metal-centred emission spectra arising from ligand-to-metal energy transfer and the emission of π → π* transitions from the phen ligand; the latter is also seen in the emission spectrum of 5.