Lanthanide complexes of tetradentate macrocyclic ligand Synthesis and spectroscopic investigation

Abstract

In the present paper, the lanthanide complexes derived from (1,5,8,12-tetraaza-2,4,9,11-tetramethyl cyclotetraaza-1,4,8,11-tetraene) were synthesized. The general composition of the complexes is [Ln(L)X 2 .H 2 O]X, where Ln = La, Ce, Nd, Sm and Eu and X = NOj and Cl - . The ligand was characterized on the basis of elemental analyses, IR, Mass and 'H NMR spectral studies. All the complexes were characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, Mass, electronic spectral techniques and thermal studies. The ligand acts as a tetradentate chelate and coordinates through four nitrogen atoms of azomethine groups. The lanthanum complexes are diamagnetic while the other Ln III complexes are paramagnetic due to the presence of 4f n unpaired electrons. The spectral parameters i.e. nephelauxetic effect (p), covalency factor (b 1/2 ), Sinha parameter (6%) and covalency angular overlap parameter (η) have been calculated from absorption spectra of Nd ΙΙΙ and Sm ΙΙΙ complexes. These parameters suggest the metal-ligand covalent bonding. In the present study, the complexes show the coordination number seven.