Synthesis and characterization of gadolinium coordination compounds containing different classes of ligands

The lanthanides ions has singular spectroscopic properties, such as strong emission lines and high color purity, allowing to synthesize luminescent coordination compounds and apply them in light emitting devices and luminescent markers. Although gadolinium is not a luminescent center, it can be used for complexes’ structural study and ligands’ triplet level determination. Here benzophenone-3 (bzf) and 2,2’-bipyridine (bipy) were used as ligands to obtain [Gd(bzf)3(bipy)] complex; bzf and Gd(NO3)3 were dissolved in ethanol and the pH were adjusted to 6-7 with triethanolamine, then bipy was dissolved in ethanol and added to the first solution, the result mixture was stirred at 50 °C for 6 h. A second complex, denoted [Gd(dpdb)3(H2O)2] was synthesized using 4-[(E)-(4-decyloxyphenyl)diazenyl]benzoic acid (dpdb), which was solubilized in DMSO and deprotonated with KOH, then Gd(NO3)3 solution was dropwised into dpdb one, then the solution was stirred at 50 °C for ~2 h. The infrared spectra show a carbonyl group displacement of bands associated with the bzf and dpdb ligands, and C-N bond in the bipy ligand. The plateau observed at 50-300 oC confirms that there no exist water molecules in the coordination sphere of gadolinium ion at [Gd(bzf)x(bipy)y] complex (Figure 1c). On the other hand the [Gd(dpdb)x(H2O)y] display a 6,2% weight loss up to 96°C, indicating the presence of water molecules, as it was expected. Elementary analysis suggests different stoichiometries according to nitrogen percentage, higher than expected for both. The possibility of ionic complexes is being investigated.