Thermodynamic and Spectroscopic Studies of Lanthanides(III) Complexation with Polyamines in Dimethyl Sulfoxide

Abstract

The thermodynamic parameters of complexation of Ln(III) cations with tris(2-aminoethyl)amine (tren) and tetraethylenepentamine (tetren) were determined in dimethyl sulfoxide (DMSO) by potentiometry and calorimetry. The excitation and emission spectra and luminescence decay constants of Eu3+ and Tb3+ complexed by tren and tetren, as well as those of the same lanthanides(III) complexed with diethylenetriamine (dien) and triethylenetetramine (trien), were also obtained in the same solvent. The combination of thermodynamic and spectroscopic data showed that, in the 1:1 complexes, all nitrogens of the ligands are bound to the lanthanides except in the case of tren, in which the pendant N is bound. For the larger ligands (trien, tren, tetren) in the higher complexes (ML2), there was less complete binding by available donors, presumably due to steric crowding. FT-IR studies were carried out in an acetonitrile/DMSO mixture, suitably chosen to follow the changes in the primary solvation sphere of lanthanide(III) due to complexation of amine groups. Results show that the mean number of molecules of DMSO removed from the inner coordination sphere of lanthanides(III) is lower than ligand denticity and that the coordination number of the metal ions increases with amine complexation from approximately 8 to approximately 10. Independently of the number and structure of the amines, linear trends, similar for all lanthanides, were obtained by plotting the values of DeltaGj degrees, DeltaHj degrees, and TDeltaSj degrees for the complexation of ethylenediamine (en), dien, trien, tren, and tetren as a function of the number of amine metal-coordinated nitrogen atoms. The main factors on which the thermodynamic functions of lanthanide(III) complexation reactions in DMSO depend are discussed.

Apparent molar volumes and compressibilities of lanthanum, gadolinium and lutetium trifluoromethanesulfonates in dimethylsulfoxide

“…However, according, to other studies, the thermodynamic aspects of lanthanide complexation with polyamides and ethylenediamine in dimethylsulfoxide, such as the trend in both DH 0 1 and DS 0 1 , indicated some changes in the average coordination number along the lanthanide series [17,39]. A similar irregularity was reported by Buenzli et al on the basis of FTIR studies of lanthanide trinitrates in the presence of DMSO in anhydrous acetonitrile [40].…”

“…Considerable efforts have been made to investigate the physicochemical properties of lanthanide complexes with polyamides and with halide ions [14,17,18]. However, data on solution densities and on the speed of sound in solutions of lanthanide ions are scarce and mainly limited to aqueous solutions [19][20][21][22].…”

Complexation of Uranium(VI) by Gluconate in Acidic Solutions: a Thermodynamic Study with Structural Analysis

“…[36][37][38] As shown in Fig. 3, complexation of Ca 2+ and the tri-, penta-, and hexavalent f-elements by acetate follows such a linear trend when the value of the stability constant for the 1:1 complex is plotted as a function of effective cationic charge.…”

Tris-(2-aminoethyl) amine as a novel and efficient tripod ligand for a copper(I)-catalyzed C–O coupling reaction

“…Recent thermodynamic and spectroscopic studies of tris-(2-aminoethyl) amine-lanthanide complexes 16 and the use of similar polyamine-CuBr complexes in polymerization reactions 17 show the significance of the tripod ligand. Very recently Chen et al demonstrated for the first time that 1,1,1-tris-(hydroxymethyl)ethane can be used as a O-donor tridentate-tripod ligand for Cu-catalyzed carbon-heteroatom bond formation.…”