Calorimetric and spectroscopic studies of Eu(III) complexation with tetramethylmalonamide and tetramethylsuccinamide in acetonitrile and dimethylsulfoxide

The complexation of Eu(III) with two N,N,N',N'-alkyl-substituted diamide li gands, tetramethylmalonamide (TMMA) and tetramethylsuccinamide (TMSA), was studied in organic solvents using titration calorimetry, FT IR and luminesc ence spectroscopy. The formation constants and enthalpy changes of the comp lexation were determined in pure acetonitrile and in acetonitrile containin g small amounts of dimethyl sulfoxide (DMSO). It was observed that TMMA for ms stronger complexes with Eu(III) than TMSA in the latter systems, which i s attributed to the structural difference between TMMA and TMSA and an entr opy effect. The effect of Eu(III) solvation by DMSO on the formation of the Eu(III)-diamide complexes is also discussed. (C) 2000 Elsevier Science S.A . All rights reserved.