Electronic Energy Levels of Dysprosium(III) ions in Solution. Assigning the Emitting State and the Intraconfigurational 4f–4f Transitions in the Vis–NIR Region and Photophysical Characterization of Dy(III) in Water, Methanol, and Dimethyl Sulfoxide

Abstract

Dysprosium­(III) ions are the third most luminescent lanthanide­(III) ions. Dy­(III) is used as dopant in optical fibers and as shift reagent in NMR imaging and is the element at the forefront of research in single-molecule magnets. Nonetheless, the excited state manifold of the dysprosium­(III) ion is not fully mapped and the nature of the emitting state has not been unequivocally assigned. In the work reported here, the photophysical properties of dysprosium­(III) triflate dissolved in H2O, MeOH, and DMSO have been studied in great detail. The solvates are symmetric, all oxygen donor atom complexes where the coordination number is 8 or 9. By comparing protonated and deuterated solvents, performing variable temperature spectroscopy, and determining the excited state lifetimes and luminescence quantum yields, the solution structure can be inferred. For the three complexes, the observed electronic energy levels were determined using absorption and emission spectroscopy. The Dy­(III) excited state manifolds of the three solvates differ from that reported by Carnall, in particular for the low lying 6F-states. It is shown that dysprosium­(III) complexes primarily luminesce from the 4F9/2 state, although thermal population of, and subsequent luminescence from the 4I15/2 state is observed. The intrinsic luminescence quantum yield is moderate (∼10%) in DMSO-d 6 and is significantly reduced in protonated solvent as both C–H and O–H oscillators act as efficient quenchers of the 4F9/2 state. We are able to conclude that the emitting state in dysprosium­(III) is 4F9/2, that the m J levels must be considered when determining electronic energy levels of dysprosium­(III), and that scrutiny of the transition probabilities may reveal the structure of dysprosium­(III) ions in solution.

Incorporation of expanded organic cations in dysprosium(III) borohydrides for achieving luminescent molecular nanomagnets

“…The rich excitation patterns (Fig. 3 i), consisting of the series of sharp peaks rather than the broad bands, indicate that the emission properties are due to the direct f–f excitation pathways as these excitation peaks can be assigned to the specific electronic transitions from the ground 6 H 15/2 multiplet to the higher-lying excited states within the Dy III centers 107 . There is no proof for an intermolecular energy transfer process which could be expected particularly for 2 incorporating expanded Ph 4 P + cations.…”

New Class of Efficient T2 Magnetic Resonance Imaging Contrast Agent: Carbon-Coated Paramagnetic Dysprosium Oxide Nanoparticles

“…Therefore, most of the PL in the DYO@C nanoparticle sample solution was due to the amorphous carbon-coating layer. Here, the emission peak at 520 nm was assigned based on energetic consideration between electronic energy levels [ 51 ] below the λ ex = 330 nm. The quantum yield (QY) of the DYO@C nanoparticle solution sample was estimated to be 6.5% using fluorescein with a QY value of 95% as the reference [ 24 ].…”

“…These were confirmed from the absorption band at λ abs-max = 260 nm in the UV-visible absorption spectrum (Figure 9a) and the emission band at λ em-max = 460 nm in the photoluminescent (PL) spectrum (excitation wavelength, λ ex = 370 nm; Figure 9b) of an aqueous solution sample, as observed in the amorphous carbon nanoparticle solution sample [24]. A PL spectrum (λ ex = 330 nm) of the aqueous Dy 2 O 3 nanoparticle solution sample, which was prepared by dispersing TGA-treated Dy 2 O 3 nanoparticles in triple-distilled water, was also taken for reference (Figure 9b), showing weak Dy-transitions at 490 nm ( 4 F 9/2 → 6 H 15/2 ) and 520 nm ( 4 I 15/2 → 6 H 13/2 ) [50,51]. Therefore, most of the PL in the DYO@C nanoparticle sample solution was due to the amorphous carbon-coating layer.…”

Combining the Best of Two Chelating Titans: A Hydroxypyridinone‐Decorated Macrocyclic Ligand for Efficient and Concomitant Complexation and Sensitized Luminescence of f‐Elements

“…Lifetime measurements of Dy(III)-DOTHOPO 4 F 9/2 ! 6 H 7/2 transition displayed a very short 2.5(2) ns decay lifetime in HEPES buffer (pH 7.4), which is likely the consequence of the very close energy levels of the Dy(III) ion [50] and DOTHOPO and, as in the case of Tb, due to the quenching of the triplet excited state by atmospheric oxygen. For Dy(III)-DOTHOPO, the increase in lifetime when going from RT to 77 K is even greater than we observed with Tb(III) ( Table S1).…”