Near-Infrared Emitting Heterobinuclear Zn-Ln (Ln = Nd, Yb, Er,and Gd) Complexes Based on a Novel Asymmetric Schiff-Base Ligand

Abstract

With the asymmetric Schiff-base zinc complex ZnL (H2L = N-(5-bromo-3-methoxysalicylidene)-N'-(5-(4-cyanophenyl)-3-methoxysalicylidene) phenylene-1,2-diamine) as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO3)3(CH3CN)] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) are synthesized by the further reaction with Ln (NO3)3·6H2O, and characterized by FT-IR, FAB-MS and elementary analysis. Photophysical studies of these complexes show that the strong and characteristic NIR luminescence of Nd3+, Yb3+and Er3+ with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer.