Synthesis, mechanism and NMR spectra of lanthanide complexes with a novel unsymmetrical Schiff base

Owing to its two unsymmetrical-NH2 groups sited on different terminals, 2, 6-diaminocaproic acid (ly-sine) was used as a reactant for synthesizing a novel unsymmetrieal Schiff base with salicylaldehyde on one side and o-vanillin on the other for the first time. It is a new way to synthesize such a special unsymmetrieal Schiff base. It is named "hetero bis-Schiff base" for distinguishing it from others. The synthesis method, formation mechanism as well as twelve new lanthanide complexes with the above ligand are reported and discussed herein. They were characterized by elementary analysis, molar conductivity, IR-spectra and especially by 1H and 13C NMR spectra. The results obtained may provide a new promising method for synthesizing similar unsymmetrieal Schiff bases and their complexes.