Hetero-binuclear near-infrared (NIR) luminescent Zn–Nd complexes self-assembled from the benzimidazole-based ligands

Abstract

With the compound [Zn(HL1)2(Py)] (H2L1=2-(1H-benzo[d]imidazol-2-yl)-6-methoxyophenol), Py=pyridine) or [Zn(HL2)2(Py)] (H2L2=2-(1H-benzo[d]imidazol-2-yl)-4-bromo-6-methoxyphenol) as the precursor, complexes [ZnLn(HL1)2(Py)(NO3)3] (Ln=Nd, 1; Ln=Gd, 2) or [ZnLn(HL2)2(Py)(NO3)3] (Ln=Nd, 3; Ln=Gd, 4) were obtained by the further reaction with Ln(NO3)3·6H2O (Ln=Nd or Gd). The result of their photophysical properties shows that the strong and characteristic near-infrared (NIR) luminescence of Nd3+ ions for complexes 1 and 3 with emissive lifetimes in microsecond range, has been sensitized from the excited state (1LC and 3LC) of the benzimidazole-based ligands, and the involvement of heavy atoms (Br) at the ligand endows the enhanced NIR luminescent property.