Lanthanide Sensitizers for Large Anti-Stokes Shift Near-Infrared-to-Visible Triplet-Triplet Annihilation Photon Upconversion.

The upconversion of near-infrared (NIR) to visible (vis) photons is of interest for display technologies and energy conversion. Although triplet-triplet annihilation (TTA) offers a mechanism for upconversion that works efficiently at low incident irradiance flux densities, current strategies for NIR-vis upconversion based on TTA have fundamental limitations. Herein, we report a strategy for NIR-vis TTA based on lanthanide-containing complexes to sensitize the upconversion. We demonstrate a ß-diketonate complex of Yb3+ paired with rubrene that emits yellow (λem = 559 nm) under NIR excitation (λexc = 980 nm). This corresponds to an exceptional anti-Stokes shift of just less than 1 eV. Thus, lanthanide complexes could unlock high-performance NIR-vis upconversion, with lanthanide sensitizers overcoming the energy loss, reabsorption, and short triplet lifetime that fundamentally limit porphyrin, nanocrystals, and direct S0-T1 sensitizers.

Strong circularly polarized luminescence of an octahedral chromium(iii) complex.

The chiral spin-flip luminophore [Cr(ddpd)2]3+ can be resolved into enantiopure material by chiral HPLC. The corresponding enantiomers show very high luminescence dissymmetry factors of up to ∣glum ∣≈ 0.093 in circularly polarized luminescence (CPL) measurements for the "ruby-like" phosphorescence transition 2E/2T1 → 4A2 in the near-IR region around λ ≈ 775 nm.

Efficient Ytterbium Near-Infrared Luminophore Based on a Nondeuterated Ligand.

A novel molecular ytterbium complex is reported with a new tetradentate ligand based on the 2,2'-bipyridine-6,6'-dicarboxylic acid scaffold. The photophysical properties are investigated, especially with respect to near-infrared luminescence. The ytterbium complex shows a rather high absolute luminescence quantum yield of Φ = 3.0% and a luminescence lifetime of τobs = 72 µs at room temperature in CD3OD solution.

Long Wavelength Excitation of Europium Luminescence in Extended, Carboline-Based Cryptates.

Two new ß-carboline-based tris(biaryl) europium cryptates are introduced. The extended antenna moiety incorporated into the cryptand frameworks enables the sensitization of europium emission with excitation wavelengths well above 450 nm. In aqueous solution, the cryptates show great complex stability, luminescence lifetimes around 0.5 ms, and absolute quantum yields of ca. 3%. In addition, the europium luminescence shows a well-defined pH-dependence in the physiologically interesting pH range 7-9.

Chiral Resolution of Lanthanoid Cryptates with Extreme Configurational Stability.

Chiral resolution is achieved for racemic tris(2,2'-bipyridine)-based lanthanoid cryptates by chiral HPLC. The resolved complexes exhibit very rare configurational stability under extreme conditions.