Luminescent properties of terbium(III) and europium(III) complexes with six 4-acetyl-bispyrazolones

Abstract

The lowest triplet energy levels of the six ligands(T) were determined to be 22989 cm⁻¹[1,3-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,3-propanedione, BPMPTD], 23148 cm⁻¹[1,4-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,4-butanedione, BPMPBD], 23419 cm⁻¹[1,5-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,5-pentane-dione, BPMPPD], 23310 cm⁻¹[1,6-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,6-hexanedione, BPMPHD], 21978 cm⁻¹[1,9-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,9-nonanedione, BPMPND] and 21930 cm⁻¹[1,10-bis-(1′-phenyl-3′-methyl-5′-pyrazolon-4′)-1,10-decanedione, BPMPDD], respectively. It was explained satisfactorily that the six ligands are more efficient for sensitizing the luminescence of Tb³⁺ than that of Eu³⁺ at room temperature, and the order of the luminescent intensities for the Tb³⁺ complexes is explained by the relative energy gap between T and ⁵ D _J of Tb³⁺ or Eu³⁺. As a conclusion, when 2700 cm⁻¹<ΔE(T-⁵ D ₄)<3000 cm⁻¹, the luminescent intensity of the Tb³⁺ complex is the strongest. This means that the lowest triplet energy level of the ligand is a chief factor to dominate RE³⁺ luminescence.