Deciphering Three Beneficial Effects of 2,2′-Bipyridine-N,N′-Dioxide on the Luminescence Sensitization of Lanthanide(III) Hexafluoroacetylacetonate Ternary Complexes

Abstract

Lanthanide hexafluoroacetylacetonate ternary complexes with 2,2 0 -bipyridine-N,N 0 -dioxide, [Ln(hfa) 3 (bpyO2)], were synthesized for Ln = Eu, Gd, Tb, and Lu and fully characterized by elemental, thermal, and mass-spectrometric analyses. The X-ray crystal structure of [Eu(hfa) 3 (bpyO2)] 3 0.5C 6 H 6 reveals an octa-coordinate metal ion lying in a severely distorted trigonal dodecahedron geometry; the EuÀO distances lie in the range 2.36À2.44 Å with no significant difference between hfa À and bpyO2. A detailed comparative photophysical investigation has been carried out to determine the exact influence of the introduction of bpyO2 in the inner coordination sphere of the metal ion in replacement of the two water molecules in [Ln(hfa) 3 (H 2 O) 2 ]. While this replacement is detrimental for Tb, it leads to a 15-fold increase in the overall quantum yield for Eu. This large improvement originates from (i) a better sensitization efficiency, the ancillary ligand being responsible for 3/4 of the energy transfer, (ii) elimination of nonradiative deactivation pathways through harmonics of OÀH vibrations, and (iii) reduction in the radiative lifetime. The latter influence is rarely documented, but it accounts here for a ≈25% increase in the intrinsic quantum yield, so that more attention should be given to this parameter when designing highly luminescent lanthanide complexes.

Lanthanide–organic frameworks constructed from naphthalenedisulfonates: structure, luminescence and luminescence sensing properties

“…13 The results highlight that 1,5-Nds is the most suitable ligand for construction of Ln 3+ complexes with a novel structure and satisfactory luminescence property. The skeleton structures of 1 and 5 are stable up to 401°C and 383°C, respectively.…”

The Radiative Lifetime in Near‐IR‐Luminescent Ytterbium Cryptates: The Key to Extremely High Quantum Yields

“…[3] Although the effect of the N-oxide moieties on t rad could not rigorously be separated from the effect of the concurrent change in the donor set, we wanted to investigate whether the same phenomenon could be observed in near-IR luminescent lanthanoid complexes and whether we could more clearly isolate the extent and nature of the operative effect on t rad .D ecreasing t rad for the sake of efficiencygains is not avery pressing need for visible emitters such as europium or terbium because very efficient systems with near-optimum quantum yields have already been developed, [1d] but this effect could greatly benefit near-IR luminophores with their low efficiencies.T herefore,w e selected ytterbium as the near-IR emitting lanthanoid of choice owing to its chemical similarity to europium and its great technological importance for photonic applications.F or the purpose of our investigation, we designed the new model cryptate 2-Yb ( Figure 1) to be as similar as possible to the known analogue 1-Yb. [3] Although the effect of the N-oxide moieties on t rad could not rigorously be separated from the effect of the concurrent change in the donor set, we wanted to investigate whether the same phenomenon could be observed in near-IR luminescent lanthanoid complexes and whether we could more clearly isolate the extent and nature of the operative effect on t rad .D ecreasing t rad for the sake of efficiencygains is not avery pressing need for visible emitters such as europium or terbium because very efficient systems with near-optimum quantum yields have already been developed, [1d] but this effect could greatly benefit near-IR luminophores with their low efficiencies.T herefore,w e selected ytterbium as the near-IR emitting lanthanoid of choice owing to its chemical similarity to europium and its great technological importance for photonic applications.F or the purpose of our investigation, we designed the new model cryptate 2-Yb ( Figure 1) to be as similar as possible to the known analogue 1-Yb.…”

“…[3] The synthetic realization of 2-Yb was straightforward and involved as the first step the reaction of bis(amine) 3 [5] and benzylic dibromide 4 [4a] in the appropriate ratio (1:2) to give the corresponding sodium cryptate 2-Na. [3] The synthetic realization of 2-Yb was straightforward and involved as the first step the reaction of bis(amine) 3 [5] and benzylic dibromide 4 [4a] in the appropriate ratio (1:2) to give the corresponding sodium cryptate 2-Na.…”

Visible-emitting hybrid sol–gel materials comprising lanthanide ions: thin film behaviour and potential use as phosphors for solid-state lighting

“…This shows that, for the polyfluorene-containing material, the absorbing state is also the emitting state, and that for the Tb-and Eu-containing materials, an energy transfer occurs from the absorbing ligands to the lanthanide ion. 4,39 The ratio between the intensity of the 5 D 0 -7 F 2 transition and that of the 5 D 0 -7 F 1 transition is a good indicator of this low-symmetry. The emission spectrum of 1 shows a structured band in the blue region with a maximum at 425 nm that corresponds to emission of the polyfluorene.…”

“…Also, the Eu III and Tb III emissions were found to be lower than those obtained in the single-emitting materials. 39,43 To probe this, we measured emission spectra at variable temperatures of a film of the composition 6 Tb : 1 Eu : 7 PhenSi 2 : 28 TEOS. These relatively poor emissive properties of the Tb III ion in this material were anticipated to result from two possible deactivation pathways of the 5 D 4 level.…”