Structural regulation and luminescence properties of Tb/Zn-Tb complexes based on aliphatic ether Schiff base

Abstract

Three new Tb(III) complexes containing bis(N-3-methoxysalicylidene)-3- oxapentane-1,5-diamine (H2L) ligand, [Tb(H2L)(NO3)3] (1), [ZnTbL(NO3)2(OAc)(MeOH)] (2), [Zn4Tb2L4(TP)2](NO3)2·DMF (3) (DMF = N,N-dimethylformamide, TP = terephthalate) have been synthesized by ether diffusion and structurally characterized. Complex 1 is a mononuclear, whereas complex 2 forms a heterodinuclear Zn-Tb cluster when introducing zinc ion into the reaction system of Complex 1. Complex 3 is a Zn-Tb heterohexanuclear cluster by adding terephthalic acid into the reaction system of complex 2. Solid-state luminescence studies show that the luminescence peaks of the ligand (π*→π) in the three complexes have undergone significant redshift and enhancement, which may be attributed to the coordination of ligand with metal ions. Moreover, the characteristic emission peak of terbium ions (5D4→7F5, at 545 nm for 2 and 546 nm for 3) appeared in heteronuclear complexes 2 and 3, while complex 1 did not. This indicates that the aliphatic ether Schiff base ligand cannot sensitize terbium ion to luminescence, while the zinc Schiff base complex [ZnL] unit can sensitize terbium ion to luminescence. Finally, the structures and luminescence properties of terbium complexes can be adjusted by the introduction of zinc(II) ion and co-ligand.