PMC

Chemical structures are shown for ligands L1–L7.

The synthesis scheme and numbering scheme for ¹H NMR of the ligands L3–L5 is shown here.

Aromatic parts of the ¹H spectra of L3–L5 in CDCl₃ at 293 K are shown.

The frontier orbitals, computed by DFT, are shown for L3–L5 in their optimized gas-phase geometries (1 eV = 8065.5 cm⁻¹)

Luminescence emission spectra are shown for [Eu₂(Lk)(hfac)₆] (k = 3–5, solid state, 293 K, ν̄_exc = 28650 cm⁻¹).

The diagram shows a representation of microstates of half-occupied polymeric linear receptors displaying a) attractive, b) negligible, and c) repulsive nearest-neighbor pair interaction energies.

Possible static geometries are shown for the central bis(benzimidazole)phenyl spacer for ligands L3–L5 in solution (point groups are given for X ≠ H, while the related point groups for X = H are given in parentheses).

Panel a) shows fluorescence and panel b) shows phosphorescence (delay time after flash 0.1 ms) spectra of [Gd₂(Lk)(hfac)₆] (k = 3–5, solid state, 77 K, ν̄_exc = 28650 cm⁻¹). The * indicates contamination with traces of highly-emissive Eu(III) cations.

The figure shows two different strategies for the introduction of lanthanide-binding sites into organic polymers. The chelating units are a) connected to the periphery (Type I) or b) incorporated within the polymer backbone (Type II).

a) Fluorescence (293 K) and b) phosphorescence (delay time after excitation flash 0.1 ms, 77 K) emission spectra are shown for L3–L5 in solution (10⁻⁴ M in CH₂Cl₂).

The figure shows the Jablonski diagram established for [Eu₂(Lk)(hfac)₆] (k = 3–5) and collects the efficiencies of intersystem crossings (η_ISC), energy transfers , intrinsic quantum yields and global quantum yields for the global ligand-mediated sensitization of Eu(III) (solid-state, 293 K). Color codes : [Eu₂(L3)(hfac)₆] = blue, [Eu₂(L4)(hfac)₆] = red and [Eu₂(L5)(hfac)₆] = green.

This simplified Jablonski diagram for [Ln₂(Lk)(hfac)₆] (k = 3–5) shows the ligand-centered triplet-mediated sensitization mechanism of the two trivalent lanthanides. , k_ISC = intersystem crossing rate constant, and .

ORTEP views of the molecular structures are shown with the numbering schemes for a) [Yb₂(L3)(hfac)₆], b) [Yb₂(L4)(hfac)₆] and c) [Eu₂(L5)(hfac)₆] in the crystal structures of 1, 3 and 4. Thermal ellipsoids are represented at the 30% probability level and hydrogen atoms are omitted for clarity.

UV-vis absorption spectra are shown for L3 (CH₂Cl₂, solid line), [Gd(hfac)₃(diglyme)₂] (CH₃CN, dashed line, ε × 2 for comparison purpose) and [Gd₂(L3)(hfac)₆] (CH₂Cl₂:CH₃CN 1:1, dotted line) recorded at 293 K. The absorption spectrum of the latter ternary complex is corrected for partial decomplexation according to equilibrium 10 with (see ).