Ligand‐Assisted Back Energy Transfer in Luminescent Tb^III Complexes for Thermosensing Properties

Abstract

A luminescent TbIII complex with a hexafluoroacetylacetone (hfa) ligand shows a characteristic back energy transfer (BEnT), which leads to high temperature sensitivity and potential application as a thermosensitive paint. Ligand‐assisted BEnT was observed when a phosphine oxide ligand was introduced into Tb(hfa)3 complex, which was shown to affect the activation energy (ΔEa) and frequency factor (A) in the BEnT process between TbIII ion and hfa ligands. According to temperature‐dependent emission‐lifetime measurements of mononuclear Tb(hfa)3 complexes with monodentate phosphine oxides and polynuclear Tb(hfa)3 complexes with bidentate phosphine oxides, the ΔEa and A values of polynuclear TbIII complexes were smaller than those of mononuclear TbIII complexes. Phosphorescence spectra and lifetimes of each Gd(hfa)3 complex revealed that excited states of hfa ligands in TbIIIcomplexes differed from those of the polynuclear TbIII complexes and mononuclear TbIII complexes. The differences in the ΔEa and A values between polynuclear and mononuclear TbIII complexes were caused by the formation of different excited states, such as delocalization of the excited state in the polynuclear TbIII complexes and localization of excited states in the mononuclear TbIII complexes. In particular, small ΔEa and A values of polynuclear TbIII complexes provided high, effective activation of the BEnT at low temperature, which resulted in high‐sensitive temperature‐dependent phosphor materials over a wide temperature range.

An Europium (III) Luminophore with Pressure‐Sensing Units: Effective Back Energy Transfer in Coordination Polymers with Hexadentate Porous Stable Networks

“…The calculated activation energy E a at around room temperature was 3.6×10 3 cm −1 . This calculated parameter is similar to that of thermo‐sensitive [Tb(hfa) 3 (tppo) 2 ] at room temperature ( E a =3.0×10 3 cm −1 ) . The Arrhenius analysis indicates that the BEnT from Eu III to the T 1 state should be activated at room temperature.…”

“…We herein select an Eu III coordination compound attached with triphenylene units for the back energy transfer (BEnT) process. The BEnT process with activation energy of the luminescence could be a key point for construction of a novel time‐resolved O 2 ‐analysis . In our previous study, an Eu III complex with triphenylene phosphine‐oxide, [Eu(hfa) 3 (dppto) 2 ] (hfa: hexafluoroacetyl‐acetonate, dppto: 2‐diphenylphosphoryl‐triphenylene), had a long T 1 lifetime on a low‐lying energy level (20,490 cm −1 ) .…”

Long‐Range LMCT Coupling in EuIII Coordination Polymers for an Effective Molecular Luminescent Thermometer**

“…On the other hand, an emission-lifetime-based temperature detection system has been focused for precise and distinguishable analysise ven under luminescents urfaces. [13][14][15][16][17] Carlos et al described an emission-lifetime-based thermometer with aw ide temperature range (12-320 K) using BEnT from the Eu III ion to 9-fluorenone-2,7-dicarboxylic acidl igands in the Eu III -MOF. [13] We have demonstrated that BEnT is strongly influenced by indirect long-range ligand-ligand electronic couplings (LECs)i n Tb III coordination polymers (Figure1a).…”

“…[13] We have demonstrated that BEnT is strongly influenced by indirect long-range ligand-ligand electronic couplings (LECs)i n Tb III coordination polymers (Figure1a). [14] Lanthanide coordination polymers showl ifetimes in the sub-millisecond range, which are longert han those of organic molecules, transition metal complexes,a nd semiconductor nanomaterials. The long emission lifetime makes it possible to time-gate out any background fluorescencefrom luminescent surfaces.…”

“…On the other hand, an emission‐lifetime‐based temperature detection system has been focused for precise and distinguishable analysis even under luminescent surfaces [13–17] . Carlos et al.…”