Picosecond time-resolved luminescence of Pr(III) complexes: Intramolecular excitation energy transfer from ligand to Pr(III)

The intramolecular excitation energy transfer from the fluorophore ligand (phens) to Pr(III) in the complexes on the basis of the picosecond time-resolved luminescence spectra is discussed. These complexes exhibit sequentially multiplex emissions from the energy levels on the ligand as π1π1* in the UV region, and from those on Pr(III) as ff in the visible region. From the decay curve analysis of these emissions, the intramolecular energy transfer pathway was clarified quantitatively following the spin-selection rule. The rate constants of energy transfer from the ligand to Pr(III) were estimated, from the π1π1* of phen to the 1I6 state of Pr(III) via the triplet state. This mechanism can be applied to control the emission properties of Pr(III) complexes by changing the emissive f-levels due to ligand variations.