Crystal structure and luminescent properties of new rare earth complexes with a flexible Salen-type ligand

A novel Salen-type ligand and its four complexes, [LnL(NO3)3] [Ln = La (1), Nd (2), Eu (3), Tb (4)], were synthesized. The X-ray single-crystal diffraction analysis indicates that the ML type complexes [LaL(NO3)3] and [NdL(NO3)3] are isomorphous. With a proton migration (or transfer) from the phenol function to the imine function, coordination of Ln to the ligand gives the ligand a zwitterionic phenoxo-iminium form. The luminescent property of the Tb(III) complex is described and some factors that influence the luminescent intensity were also discussed.