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

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 Zn₂Ln ₂-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 Nd^{3 +}, Yb^{3 +} or Er^{3 +} ions and visible luminescence of Tb ^{3 +} 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 Eu^{3 +} ions, the Eu^{3 +}-based emissions are quenched in complex 5.