Sm(III) complexation with small peptides.: Crystal structure of [SM2(Gly-Val)4(H2O)8](ClO4)6•2H2O

in this work, samarium(III) complexes with small peptides have been studied by potentiometric measurements. Experiments were performed in aqueous solution at 37.0degreesC and 0.15 M NaClO4, resembling physiological medium. Low stability Sm(III)-peptide complexes were detected. Complexes with 1:1 ligand to metal molar ratio are predominant in the studied conditions. For Gly-Gly, the smallest dipeptide, [Sm(HL)(2)](3+) was also detected. For pH values greater than 6, hydrolysis to [Sm(OH)](2+) and Sm(OH)(3) becomes the main process. One of these complexes was isolated and characterized in the solid state. X-ray structure of [Sm-2(GlyVal)(4)(H2O)(8)](ClO4)(6)(.)2H(2)O is here reported. In this dimeric complex, two samarium. atoms, with coordination number nine, are connected via four bridging carboxylate groups. (C) 2003 Elsevier B.V. All rights reserved.