Lanthanide complexes with compartmental schiff bases

Lanthanide complexes have been prepared with acyclic and cyclic compartmental Schiff bases (H2L) obtained by condensation of 2,6-diformyl-4-chlorophenol and the polyamines NH2(CH2)2X(CH2)2NH2 (X = NH, S). They can be formulated as Ln(L)NO3· nH2O or Ln(H2L)(NO3)3·nH2O (Ln3+ = La, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb; n = 0-5) and have been obtained by step-by-step reactions, which allow a more appropriate control of the reaction procedure. Template syntheses often produce not well defined complexes. The Schiff bases act as neutral of dinegative chelating ligands according to the experimental conditions employed. When they coordinate as neutral ligands, one ionic and two bidentate nitrate groups are present in the complexes. A ring contraction, through an interanl cyclization, has been observed in the macrocyclic complexes when X = NH (H2Lc). The crystal structure of [Tb(H2Lc)(NO3)2]NO3 was determined by X-ray crystallography. The compound is monoclinic, space group C2/c, with a = 23.668(5), b = 14.328(7), c = 19.482(5) Å and ? = 91.82(5)°; Dc = 1.70 g cm-3 for Z = 8. The structure was refined to R = 0.078. The terbium ion is nona-coordinated in the usual coordination geometry of a distorted tricapped trigonal prism. Two nitrato groups are chelate in approximately bisphenoidal position, the third nitrate being ionic. The organic macrocycle is coordinated through two oxygen and three nitrogen atoms. Selected bond distance are: Tb?O(nitrate) 2.46 Å (mean), Tb?O(ligand) 2.25 Å (mean), Tb?N(ligand) 2.54 Å (mean).