Effective enhancement of near-infrared emission by carbazole modification in the Zn-Nd bimetallic Schiff-base complexes

With ZnL1 or ZnL2 from the simple Salen-type Schiff-base ligand H2L1 (H2L1 N,N'-bis(3-methoxysalicylidene)-ethylene-1,2-diamine) or the carbazole-modified Salen-type Schiff-base ligand H2L2 (H2L2 N,N'-bis(3-methoxy-5-{2-[4-(N-carbazyl)-phenyl]-ethynyl}-ethylene-1,2-diamine) as the precursor, two series of four bimetallic ZnLn complexes (Ln=Nd(1 or 3), Ln=Gd (2 or 4) are obtained, respectively. The photophysical properties results showed that the sensitization from the excited state ((LC)-L-1 and (LC)-L-3) of the ligand H2L1 or H2L2 and the effective energy transfer of Zn2+-Schiff-base (ZnL1 or ZnL2) to the Nd3+ ion for the NIR luminescence were realized, respectively. Especially through the cabarzole modification, the improved NIR luminescence of the ZnNd complex 3 was observed due to the realization of the energy level's match of the excited state of the chromophore to the Nd3+ ion's exciting state. (C) 2012 Elsevier B.V. All rights reserved.