Preparation and characterization of lanthanide(III) complexes with polybenzimidazole ligands. Crystal structure of bis[tris(N-methyl-1-benzimidazol-2-yl)amine]lanthanum(III) perchlorate monoacetonitrile solvate

Complexes with the composition [Ln(L-1)(2)](ClO4)(3) . mCH(3)CN . nH(2)O an d [Ln(L-2)(2)](ClO4)(3) . mCH(3)CN . nH(2)O (Ln = La, Sm, Eu, Tm; L-1 = tri s(N-methyl-1-benzimidazol-2-yl)amine, L2 = tris (N-ethyl-1-benzimidazol-2-y l) amine; m n = 0 or 1)have been characterized by infrared absorption spect roscopy (for the former) and elemental analysis. The X-ray crystal structur e of the complex [La(L-1)(2)](ClO4)(3) . CH3CN (La-l) has been determined. La-l crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 12 .882(4), b = 21.100(6), c = 22.706(6) and Z = 4. The coordination geometry about the lanthanum(III) ion is best described as a slightly distorted tria ngulated dodecahedron comprising eight nitrogen atoms from two tetradentate ligands (L-1).