A terpyridyl-imidazole based europium tris-(β-diketonate) complex as an efficient molecular luminescent thermometer and single component white light emitter via synergy in energy transfer between ligands and Eu³⁺

Abstract

A europium tris-(β-diketonate) complex coupled with a terpyridyl-imidazole motif acts as an efficient luminescent thermometer and single component white light emitter via mutual energy transfer among ligands and Eu3+.

Terpyridyl-Imidazole Based Ligand Coordinated to Ln(Hexafluoroacetyl acetonate)3 Core: Synthesis, Structural Characterization, Luminescence Properties, and Thermosensing Behaviors in Solution and PMMA Film

“…Hence, simply by replacing the antenna ligand from tta to hfa, a huge modulation of intercomponent energy transfer is achieved in the respective Eu III complex, which is also mirrored in its photoluminescence spectral behavior. Additionally, diminution of Eu III -centered emission intensity and lifetime upon temperature rise can be attributed to the involvement of the low-lying LMCT state, which is not very unusual in such Eu III -complexes, as the reduction potential for the Eu III /Eu II couple is very low (−0.35 V). ,,,− On the other hand, a systematic increase in the ligand-centered emission peak at ∼465 nm upon the rise in temperature may be ascribed to LMCT-state mediated back-energy transfer to the S 1 state of tpy-HImzphen . Complex 3 exhibits very low relative emission intensity and lifetime associated with the Sm III -centered electric dipole peak at ∼646 nm.…”

“…38,45,46 As per our literature survey, Ln III -based discrete molecule luminescent thermometers are relatively less explored, 37,39,47−54 while reports on terpyridyl-ligand-based lanthanide luminescent thermometers are even more sparse. 55 In our recent report, we have designed a series of lanthanide(III) complexes comprising 2-theonyltrifluoroacetonate (tta) and the same terpyridyl-imidazole ligand (tpy-HImzphen) and investigated their dissimilar luminescence characteristics. 29 We noticed that only Eu III among the four lanthanides (La III , Eu III , Sm III , and Tb III ) gets substantially sensitized.…”

“…29 We noticed that only Eu III among the four lanthanides (La III , Eu III , Sm III , and Tb III ) gets substantially sensitized. However, the cumulative energy transfer from tta as well as from tpy-HImzphen to Eu III is quite low (η sens = ∼37%), 55 despite maintaining the required energy gap between the lowest triplet state (T 1 ) of the ligands and the lowest emissive state of Eu III ( 5 D 0 ). Herein, we considered replacing the tta moiety with another fluorinated β-diketonate moiety having a higher T 1 level (∼22000 cm −1 ) than that of tta (∼21000 cm −1 ) so that intercomponent energy transfer from ligand-to-metal becomes more facile.…”

“…Luminescent lanthanide complexes are now emerging as the next-generation tools for precise measurement of temperature over traditional thermometers in medical and industrial applications, mostly owing to their noninvasive nature and nanoscale miniaturization. − Lanthanide luminescent thermometers possess all the necessary criteria to be suitable for luminescence thermometry, viz., intense luminescence with high-temperature sensitivity as well as photostability, a longer decay time, and thermostability. , Most of the earlier reported luminescent lanthanide thermometers are either lanthanide-based coordination polymers , or mix-doped MOFs. ,, As per our literature survey, Ln III -based discrete molecule luminescent thermometers are relatively less explored, ,,− while reports on terpyridyl-ligand-based lanthanide luminescent thermometers are even more sparse …”

The influence of different cations on the structure and spectral properties of Ln3+ tetrakis-complexes with the CAPh-type ligand dimethyl-N-trichloroacetylamidophosphate

“…Lanthanide complexes with organic ligands that have narrow emission bands and long luminescence lifetimes attract the attention of researchers due to their potential applicability in organic light emitting device (OLED) technology, photoluminescent labels in biological systems, luminescent thermometers, pressure sensors, solar cells, etc. 1–8 An organic ligand, also called “antenna”, is used as a sensitizer which transfers absorbed incident light energy to the lanthanide ion that emits in a characteristic wavelength. 9–11 A prominent place among the substances-sensitizers of Ln 3+ emission belongs to bidentate chelating ligands such as carbacylamidophosphates (P,N-heterosubstituted analogs of β-diketones, with the chelating fragment C(O)N(H)P(O)) and sulfonylamidophosphates (S,P,N-heterosubstituted analogues of β-diketones, with the chelating fragment S(O)N(H)P(O)).…”