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.