Thermally-assisted photosensitized emission in a trivalent terbium complex

Abstract

Luminescent lanthanide complexes containing effective photosensitizers are promising materials for use in displays and sensors. The photosensitizer design strategy has been studied for developing the lanthanide-based luminophores. Herein, we demonstrate a photosensitizer design using dinuclear luminescent lanthanide complex, which exhibits thermally-assisted photosensitized emission. The lanthanide complex comprised Tb(III) ions, six tetramethylheptanedionates, and phosphine oxide bridge containing a phenanthrene frameworks. The phenanthrene ligand and Tb(III) ions are the energy donor (photosensitizer) and acceptor (emission center) parts, respectively. The energy-donating level of the ligand (lowest excited triplet (T1) level = 19,850 cm−1) is lower than the emitting level of the Tb(III) ion (5D4 level = 20,500 cm−1). The long-lived T1 state of the energy-donating ligands promoted an efficient thermally-assisted photosensitized emission of the Tb(III) acceptor (5D4 level), resulting in a pure-green colored emission with a high photosensitized emission quantum yield (73%).

Tuning the Emission of Homometallic DyIII, TbIII, and EuIII 1-D Coordination Polymers with 2,6-Di(1H-1,2,4-triazole-1-yl-methyl)-4-R-phenoxo Ligands: Sensitization through the Singlet State

“…Alternatively, measurements of the T 1 lifetimes might provide further valuable information. , A longer lifetime (>1 ms) allows sufficient time for populating the T 1 state and transferring energy to the Ln III ions. On the other hand, a shorter lifetime (in the order of microseconds) indicates a weak population of this level.…”

Current Development of Lanthanide Complexes for Biomedical Applications

“…Therefore, the long-lasting T 1 excited state promotes efficient T 1 !Ln* energy transfer and enables efficient population of Ln(III) emitting states, even if the energy of T 1 excited state of ligand is equivalent to or lower than that of Ln* state (which cause back energy transfer (BEnT), Figure 2b). [45][46][47] On the other hand, the evaluation of the energy transfer process T 1 !Ln* can be represented as sensitization efficiency (η sens ) described in equation (1). The 4 f-4 f transition including radiative rate (k r ) and nonradiative rate (k nr ) constants are expressed in equation ( 2).…”

“…Therefore, the long–lasting T 1 excited state promotes efficient T 1 →Ln* energy transfer and enables efficient population of Ln(III) emitting states, even if the energy of T 1 excited state of ligand is equivalent to or lower than that of Ln* state (which cause back energy transfer (BEnT), Figure 2b). [45–47] …”

Effective photosensitized emission of a Tb(iii) complex using a β-diketonate photosensitizer and an oxygen barrier system in a thermally populated triplet state

“…24 The photosensitization model with a low T 1 level is beneficial for enhancing the brightness of Tb( iii ) emission (ESI in ref. 25). 25 However, the emission intensity of the Tb( iii ) luminophores is diminished by triplet oxygen quenching when using long-lived T 1 photosensitizers.…”

“…25). 25 However, the emission intensity of the Tb( iii ) luminophores is diminished by triplet oxygen quenching when using long-lived T 1 photosensitizers. 10,26–31…”