Responsive, Water‐Soluble Europium(III) Luminescent Probes

A new phosphor of the type Gd Eu V O (x=0-1.0) was synthesized through the solid-state reaction ceramics method. A pure phase formation was verified by using X-ray powder diffraction measurements. The luminescence of Gd V O :Eu was investigated through optical and laser excitation spectroscopy. The luminescence curves were investigated in the temperature region 10 to 300 K. Gd V O shows a self-activated luminescence under excitation with UV- and near-UV light. The spectra, the decay lifetimes, and the thermal stability of Gd Eu V O (x=0.005-1.0) strongly depend on both the Eu concentration and the temperature. The tunable luminescence is realized by controlling the Eu -doping level to adjust the host energy-transfer efficiency from the VO groups to the Eu activators. At low Eu concentrations (<30 mol %), the intensity and lifetime show an unusual change with an increase of the temperature from 10-300 K, that is, the luminescence experiences a straightforward enhancement. The energy transfer from the VO group to the Eu ions could be accelerated with an increase of the temperature resulting in an unusual enhancement of the Eu luminescence and lifetime. However, the emission of the Eu ions decreased for highly Eu-doped samples (>30 mol %) with an increase of the temperature. The luminescence mechanism was discussed on the basis of the charge-transfer band of the Eu ions, the doping concentration, and the proposed microstructures in the lattices.

“…In particular, the 5 D 0 state is a single level without any Stark splitting in any hosts. This can avoid the convolution of overlapping luminescence lines from different energy levels …”

Section: Introductionsupporting

confidence: 89%

“…This can avoid the convolution of overlapping luminescence lines from different energy levels. [8][9][10] Brusset et al [11,12] firstly reported the rare-earth vanadate T 8 V 2 O 17 ,where Trepresents aREi on site. However,the detailed structure is still controversial.…”

Section: Introductionmentioning

confidence: 99%

Eu³⁺‐Activated Gd₈V₂O₁₇: Energy Transfer, Luminescence, and Temperature‐Dependence Characteristics

Deng

Liu

Zhou

et al. 2018

“…Instead, the Raman intensities almost exponentially vanish with increasing peptide concentrations, while the ROA/ CID values exhibit maxima at optimal peptide–complex ratios of around 4–7. One may speculate that more peptide molecules become bonded to the complex; however, the actual cause of the concentration dependence will likely be quite complicated, including luminescence quenching by the peptide and possible binding and decomposition of the complex by peptide impurities (mostly trifluoroacetic acid from the synthesis) at very high peptide concentrations.…”

Section: Titration Curvesmentioning

confidence: 99%

Binding of Lanthanide Complexes to Histidine‐Containing Peptides Probed by Raman Optical Activity Spectroscopy

Brichtová

Hudecová

Vršková

et al. 2018

Lanthanide complexes are used as convenient spectroscopic probes for many biomolecules. Their binding to proteins is believed to be enhanced by the presence of histidine, but the strength of the interaction significantly varies across different systems. To understand the role of peptide length and sequence, short histidine-containing peptides have been synthesized (His-Gly, His-Gly-Gly, His-Gly-Gly-Gly, Gly-His, Gly-His-Gly, His-His, and Gly-Gly-His) and circularly polarized luminescence (CPL) induced at the [Eu(dpa) ] complex has been measured by means of a Raman optical activity (ROA) spectrometer. The obtained data indicate relatively weak binding of the histidine residue to the complex, with a strong participation of other parts of the peptide. Longer peptides, low pH, and a histidine residue close to the N-peptide terminus favor the binding. The binding strengths are approximately proportional to the CPL intensity and roughly correlate with predictions based on molecular dynamics (MD) simulations. The specificity of lanthanide binding to the peptide structure and its intense luminescence and high optical activity make the ROA/CPL technique suitable for probing secondary and tertiary structures of peptides and proteins.

“…Lanthanide (Ln) complexes have attracted great interest over the past two decades due to their stability, flexible coordination ability,a nd unique photophysical properties. [9][10][11][12] Lanthanidec omplexes have been widely used as luminescent probes, MRI contrast agents, luminescentm etal-organic frameworks, and cellular imaging agents. [11] Very recently,P atra and co-workersr eported the synthesis of Eu III and Tb III complexes containing2 -alkenoylpyridine and three small 1,3-diketone ligands, which weres ubsequently found to present strong luminescence and display good binding affinity towards DNA and human serum albumin( HSA, Scheme1a).…”

Section: Introductionmentioning

confidence: 99%

Enantioselective [2+2] Photocycloaddition Reactions of Enones and Olefins with Visible Light Mediated by N,N′‐Dioxide–Metal Complexes

Han

Dong

Yao

et al. 2018

A 2‐alkenoylpyridine‐bound N,N′‐dioxide–TbIII complex has been found to absorb visible light to reach the excited state, leading to the direct visible‐light‐excited catalytic enantioselective [2+2] cycloaddition of 2‐alkenoylpyridines to various alkenes in the absence of an additional photosensitizer. Diverse enantioenriched cyclobutanes were successfully obtained (yields up to 70 %, >19:1 d.r., 92 % ee). The new chiral terbium(III) complex features a bathochromic shift, lower excitation energy, and facile intersystem crossing due to paramagnetic and heavy‐atom effects, which enable the antenna 2‐alkenoylpyridines to be excited. For comparison, a chiral N,N′‐dioxide–ScIII complex in combination with [Ru(bpy)3]Cl2 was efficient in the enantioselective photocycloaddition reactions of 2′‐hydroxychalcones with alkenes, thereby revealing that both substrates and metal salts have significant effects on the reaction.