Photo-luminescent hetero-tetranuclear Zn2Ln2 (Ln = Nd, Yb, Er, Gd, Eu or Tb) complexes self-assembled from the benzimidazole-based HL and bpe

• Zn2Ln2-arrayed complexes from the benzimidazole-based ligand
• Sensitization and energy transfer
• Energy level match and charge transfer

Through the self-assembly of the benzimidazole-based ligand HL (HL = 2-(1H-benzo[d]imidazol-2-yl)-6-methoxyohenol) with Zn(OAc)2, Ln(NO3)3 (Ln = Nd, Yb, Er, Gd, Eu or Tb) and bpe (bpe = trans-bis(4-pyridyl)ethylene), six hetero-tetranuclear Zn2Ln2-arrayed complexes (Ln = Nd, 1; Yb, 2; Er, 3; Gd, 4; Eu 5; or Tb, 6) are obtained, respectively. The result of their photophysical properties shows that the characteristic near-infrared (NIR) luminescence of Nd3 +, Yb3 + or Er3 + ions and visible luminescence of Tb3 + ions with emissive lifetimes in microsecond ranges have been sensitized from the excited states (1LC and 3LC) of the benzimidazole-based ligand, while due to the charge-transfer process from the ligand excited state to the Eu3 + ions, the Eu3 +-based emissions are quenched in complex 5.

Series of hetero-tetranuclear Zn2Ln2 complexes [Zn2Ln2(L)4(bpe)(NO3)6] (Ln = Nd, 1; Yb, 2; Er, 3; Gd, 4; Eu 5; or Tb, 6) were synthesized and characterized. Their photophysical properties show that the characteristic near-infrared (NIR) emissions of Nd3 +, Yb3 + and Er3 + ions for 1–3 + and visible emissions of Tb3 + ion for 6 are sensitized from the excited states (1LC and 3LC) of the mixed ligands, while the Eu3 +-based emissions are quenched in 5 due to charge-transfer process.Figure optionsDownload as PowerPoint slide