Sm(III) complexation with alpha-amino acids X-ray crystal structure of [Sm-2(Hala)(4)(H2O)(8)](ClO4)(4)(Cl)(2)

Sm(III) coordination compounds are currently used as radiotherapeutic agent s. Moreover, it is known that tumour cells show enhanced intake of or-amino acids (H(n)aa). With this in mind, the study of samarium complexes with th ese ligands has obvious interest. In this work, potentiometric studies of S m(LU) in the presence of glycine, alanine, proline, tryptophane, valine, gl utamic acid and cysteine have been carried out. Experiments were performed in aqueous solution ([Sm3+] = 5.0-60.0 mM) at 37 degreesC and 0.15 M NaClO4 . Mono and dinuclear species were detected in the pH range 1.5-5.3, For hig her pH values, Sm(OH)(3) competes with the formation of Sm complexes. In ad dition, Sm(III)-H(n)aa complexes were isolated and characterized at solid s tate. The structure of [Sm-2(Hala)(4)(H2O)(8)](ClO4)(4)(Cl)(2) is reported. In this complex, two Sm centres are joined by four mu -COO bridges. Four m olecules of water complete the positions of each eight-coordinate Sm atom. (C) 2001 Elsevier Science B.V. All rights reserved.