Circularly Polarized Luminescence from an Eu(III) Complex Based on 2-Thenoyltrifluoroacetyl-acetonate and a Tetradentate Chiral Ligand

Abstract

A new chiral complex {[EuL(tta)(HO)]CFSO; L = N, N'-bis(2-pyridylmethylidene)-1,2-( R, R + S, S)-cyclohexanediamine; tta = 2-thenoyltrifluoroacetyl-acetonate} has been synthesized and characterized from a structural and spectroscopic point of view. The molecular structure in the solid state shows the presence of one chiral L, two tta, and one water molecules bound to the metal center. L and tta molecules can efficiently harvest and transfer to Eu(III) the UV light absorbed in the 250-400 nm range. The forced electric-dipole D → F emission band dominates the Eu(III) emission spectra recorded in the solid state and in solution of acetonitrile or methanol and the calculated intrinsic quantum yield of the metal ion is around 40-50%. The light emitted by the enantiopure complex shows a sizable degree of polarization with a maximum value of the emission dissymmetry factor ( g) equal to 0.2 in methanol solution. If compared with the complex in the solid state or in acetonitrile solution, then the first coordination sphere of Eu(III) when the complex is dissolved in methanol is characterized by the presence of one CHOH molecule instead of water. This fact is related to different Eu(III) CPL signatures in the two solvents.

Binuclear Lanthanide(III) Complexes with Chiral Ligands: Dynamic Equilibria in Solution and Binding with Nucleotides Studied by Spectroscopic Methods

“…CPL signals of 5 D 0 → 7 F 1 decrease significantly, and the peak at 2001 cm −1 almost disappears at concentration of 1.3 mM. The weakest CPL curve of 5 D 0 → 7 F 1 transition is similar to that of previously reported mononuclear chiral Eu(III) complex derived from N,N’‐bis(2‐pyridylmethylene),2‐diamine, indicating that most of the binuclear complex dissociated into monomer under this condition.…”

Lanthanide‐Based Complexes Containing a Chiral trans‐1,2‐Diaminocyclohexane (DACH) Backbone: Spectroscopic Properties and Potential Applications

“…DFT calculations performed on all the Y(III) analogues, as its complexes present similar structural features to Eu(III) but have no unpaired electrons, thus improving the speed of calculation, [61] considering solvent explicitly, revealed the presence of two water molecules directly bound to Y(III) (Figure 10). This result was confirmed also by calculations where up to 5 water molecules were added in the proximity of the metal ion which produced all final structures with only two waters directly bound and the others forming H‐bonds in second sphere [65] …”

Solid‐State Near‐Infrared Circularly Polarized Luminescence from Chiral YbIII‐Single‐Molecule Magnet

“…Among them, the highest value of g lum =1.38 measured for the Cs[Eu((+)‐hfbc) 4 ] complex (where hfbc=3‐heptafluoro‐butylryl‐(+)‐camphorato) [7] . Another chemical approach is to associate achiral Ln(β‐diketonate) n (2≤n≤4) units to chiral ligands such as binaphtyl derivatives, [8] cyclohexane diamine, [9] or pyridinebisoxazoline [10] . In the near infrared (NIR) region i. e. from 700 to 1300 nm, Nd III and mostly Yb III ‐centered emissions are likely to be favoured, even if NIR‐CPL studies for these ions remain scarce [10,11] …”