Gadolinium(III) and europium(III) l-glutamates: Synthesis and characterization

Two lanthanide(III) complexes with l-glutamate ligands [{Ln₂(l-Glu)₂(H₂O)₈} · 4(ClO₄) · 2.5H₂O]_n (Ln = Gd (1), Eu (2)) have been prepared and characterized by single-crystal X-ray diffraction. The compounds are isomorphous with infinite cationic 2D layers stacked together by secondary bonds. The building blocks are slightly different non-centrosymmetric dinuclear units placed in alternating layers, the resulting structures thus containing four non-equivalent Ln metal sites. The dinuclear units contain a fourfold bridge, two in the η¹:η¹:μ₂ and two in the η²:η¹:μ₂ modes, from two α- and two γ-carboxylates of four different l-Glu residues, respectively.