Synthesis, Characterization and Photophysical Study of 4,4’-Diamino-2,2’-stilbenedisulfonate with Lanthanide Ions Complexes

Complex of 4,4’-diamino-2,2’-stilbenedisulfonic acid (DSD) with trivalent lanthanide ions Eu3+ and Tb3+ were prepared at the ratio of 3:1 (DSD:Ln). The complexes with ions present in the form of powder show black (Eu3+) and brown (Tb3+) colors. The complexometric titration and CHN elemental analysis suggest that these complexes have the general formula Eu(C14H12N2SO3SO3H)3∙3H2O and Tb(C14H12N2SO3SO3H)2(CF3SO3)∙3H2O. The shift of the 330 nm band for DSD to a longer wavelength in the infrared spectra of the complexes and the disappearance of the bands at 2921 and 2623 cm-1 are indicative of the formation of complexes with ions Eu3+ and Tb3+. Thermal analysis shows that DSD is thermally stable up to 573 K and the decomposition process of the complexes shows two and three mass losses for ions Eu3+ and Tb3+, respectively. The analysis of luminescence indicates that the complexes do not present the emission from the lanthanide moiety in the visible region. This may be related to the ligand triplet states, which are probably at lower energy than the emission state of the Eu3+ (5D0) and Tb3+ (5D4) ions.