Synthesis, structure and near-infrared (NIR) luminescence of series of Zn2Ln (Ln = Nd, Yb or Er) complexes based on the Salen-type Schiff-base ligand with the flexible linker

Abstract

Abstract With the Zn-Schiff-base [ZnL(CH 3 CN)] from the Salen-type Schiff-base ligand H 2 L (H 2 L = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) with the flexible linker as the precursor, a series of hetero-trinuclear Zn 2 Ln complexes [Zn 2 Ln(L) 2 (Cl) 3 ] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) are obtained by the further reaction with LnCl 3 ·6H 2 O, respectively. The results of their photophysical studies show that the strong and characteristic NIR luminescence with emissive lifetimes in the microsecond range, has been sensitized from the excited state (both 1 LC and 3 LC) of the ligand due to the effective intramolecular energy transfer.