Sensitization of Yb(III), ER(III), and Nd(III) Luminescence by Ligands Based on 3-Formyl-4-Hydroxybenzoic Acid and Transition Metals.

The syntheses of 3-formyl-4-hydroxybenzoic acid-derived ligands from ethylenediamine, diethylenetriamine, and triethylenetetramine are described. These ligands can further form hetero-binuclear complexes with transition metal ions (M2+ = Zn2+, Fe2+, Ni2+, Mn2+) and lanthanide ions (Ln3+ = Nd3+, Er3+, Yb3+). The spectroscopic properties were studied using near-infrared (NIR) luminescence emission spectra, fluorescence lifetime, and quantum yield. These hetero-nuclear complexes exhibited the characteristic lanthanide near-infrared luminescence in the solid state through energy-transfer from the chromophore to lanthanide ions. The d-block emission bands of transition metal ions in the solid state overlapped with f–f absorption bands of Yb(III), Er(III), or Nd(III), sensitizing the near-infrared luminescence of these hetero-binuclear complexes. [ABSTRACT FROM AUTHOR]