N, N′-Ethylene-bis(3-methoxysalicylideneimine) mononuclear (4f) and heterodinuclear (3d–4f) metal complexes: Synthesis, crystal structure and luminescent properties

Abstract

The stepwise synthesis of mononuclear (4f) and heterodinuclear (3d–4f) Salen-like complexes has been investigated through structural determination of the intermediate and final products occurring in the process. In the first step, reactions of ligand H 2L and Ln(NO 3) 3 · 6H 2O give rise to three mononuclear lanthanide complexes Ln(H 2L)(NO 3) 3 [H 2L = N, N′-ethylene-bis(3-methoxysalicylideneimine), Ln = Nd ( 1), Eu ( 2) and Tb ( 3)], in which N, N′-ethylene-bis(3-methoxysalicylideneimine) acts as tetradentate ligands with the O 2O 2 set of donor atoms capable of effective coordination. These species are fairly stable and have been isolated. Then, addition of Cu(Ac) 2 · H 2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes Cu(L)Ln(NO 3) 3 · H 2O [Ln = Nd ( 4) and Eu ( 5)] where the Cu(II) ion is inserted to the inner N 2O 2 cavity. Luminescent analysis reveals that complex 3 exhibits characteristic metal-centered fluorescence of Tb(III) ion. However, the characteristic luminescence of both Sm(III) and Eu(III) ions is not observed both in solution and solid state of the complexes.