Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L1 , L2 and L3 , has been investigated.The Schiff base macrocycle L1 and its corresponding reduced ligand L2 arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L3 is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L1 and L2 have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L1 give the expected [1:1, Ln:L1 ] stoichiometry; however, complexes obtained with L2 show a [2:1, Ln:L2 ] stoichiometry. Finally, complexation reactions with L3 have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.