Studies on Lanthanide Complexes of the Tripodal Ligand Tris(benzimidazol-2-ylmethyl)amine (ntb). Crystal Structures of [Ln(ntb)(NO3)3].H2O (Ln = Ce, Er)

The tripodal ligand tris(benzimidazol-2-ylmethyl)amine (ntb) reacts with lanthanide nitrates in methanol to give the mononuclear complexes [Ln(ntb)(NO3)3].H2O (Ln = La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Er) which have been characterized by elemental analyses, infrared, electronic and 1H n.m.r. spectroscopies, X-ray diffraction patterns, and conductivity measurements. The crystal and molecular structures of two complexes [Ln(ntb)(NO3)3].H2O (Ln = Ce, Er) have been determined. The cerium complex crystallizes in the monoclinic system, space group C2/c with a 26·79(1), b 14·497(8), c 17·20(1) Å, β 99·06(4)°, V 6596(6) Å3 , Z 8, while the erbium complex crystallizes in the cubic system, space group Pa-3 with a 18·2504(1) Å, V 6078·79(6) Å3, Z 8. In both cases the central metal ions are coordinated to the four nitrogen atoms of ntb and six oxygen atoms of three chelating nitrate groups. The total coordination number of the metal ion is 10. Spectroscopic analyses suggest that other complexes show a similar coordination mode. The fluorescence properties of the samarium(III), europium(III), terbium(III), and dysprosium(III) complexes were investigated.