A Promising Change in the Selection of the Circular Polarization Excitation Used in the Measurement of Eu(III) Circularly Polarized Luminescence

Abstract

A judicious change in the selected transition used for circular polarization excitation will overcome the low oscillator strength limitation of the currently allowed magnetic-dipole 5 D 1 ← 7 F 2 (Eu(III)) transition chosen for circularly polarized luminescence (CPL) measurement. The proposed allowed magnetic-dipole 5 D 1 ← 7 F 0 (Eu(III)) transition will facilitate the detection of CPL from the Eu(III) systems of interest. CPL on the acetonitrile solution of the chiral tris complex of Eu(III) with (R,R)-, recently suggested as an effective and reliable CPL calibrating agent, confirms the feasibility of the proposed experimental procedure. A comparable CPL activity exhibited by the acetonitrile solution of [Eu((R,R)-1) 3 ] 3+ following direct excitation in the spectral range of the 5 D 1 ← 7 F 0 transition and upon indirect excitation through the ligand absorption bands (λ exc = 308 nm) was observed. This confirms that the recommended magnetic-dipole allowed absorption transition, 5 D 1 ← 7 F 0 , is the transition to be considered in the measurement of CPL. This work provides critical direction for the continued instrumental improvements that can be done for developing CPL into a biomolecular structural probe.

Structural and Photophysical Properties of Visible- and Near-IR-Emitting Tris Lanthanide(III) Complexes Formed with the Enantiomers of N,N′-Bis(1-phenylethyl)-2,6-pyridinedicarboxamide

“…37, 39, 65, 69–71 A similar conclusion was also drawn from the CPL measurements. 36, 38 It was found that the strong CPL activity exhibited by [Eu L 3 ] 3+ (e.g. g lum value amounted to −0.19 at 590 nm for L = ( R , R )– 1 ) is comparable when either a direct excitation of the Eu(III) ion in the spectral range of the 5 D 0 → 7 F 1 transition or an indirect excitation through the ligand absorption bands was used but also is independent of the polarization of the excitation beam (e.g.…”

“…This was consistent with the presence of only one diastereomeric species in solution. 27, 28, 38, 71, 72 On the other hand, one would have expected that the CPL would have been dependent on the excitation polarization if the solution would have contained a mixture of diastereoisomers. 73, 74 This is also in good agreement with the X–ray crystal structures of [Ln L 3 ] 3+ (Ln(III) = Eu, Gd, Tb, Yb and L = ( R , R )– 1 and ( S , S )– 1 ) showing the formation of triple helical complexes in the solid state (see below).…”

“…Although the sensitization of these Ln(III) ions was relatively weak due to poor energy transfer processes, one can envision to use these stable [Ln L 3 ] 3+ complexes for their chiroptical properties (i.e. large CPL activities observed) 36, 38, 77 to develop reliable empirical relationships between chiral structures and CPL sign patterns. Of special importance, one may be able to develop a “helicity rule” aimed at determining a Δ or Λ helicity configuration based upon CPL sign patterns from such Ln(III)–containing systems or related compounds emitting in the VIS and NIR regions.…”

Synthesis, Crystal Structure, Luminescence and Thermal Stability of a New Coordination Polymer Constructed by Europium(III) and 2,4‐Dichlorophenoxyacetate

“…In the second stage, the turning point temperature of the fastest weight loss is 309.01 ℃, and the weight-loss ratio is 47.73% (calculated 47.03%), which could be attributed to the removal of four water molecules and four 2,4-dichlorophenoxy acetic acid anions. In the last stage, the weight-loss ratio is 15.77% with the turning point temperature of the fastest weight loss at 625.85 ℃ (calculated 15.86%), corresponding to the scrap (C 16 …”

“…9,10 Lanthanide aromatic carboxylate complexes often show distinctive molecular structures because lanthanide ions have larger radii and higher variable coordination numbers than transitional metals, 11,12 and aromatic carboxylic acids have a variety of coordination modes. A large number of lanthanide aromatic carboxylate complexes have dimer and polymeric structures, [13][14][15][16] and they have also good luminescence and thermal stability. [17][18][19][20] So it is interesting to study lanthanide complexes with aromatic carboxylic acids as the ligands.…”