Bridged Aromatic Oxo- and Thioethers with Intense Emission in Solution and the Solid State

Abstract

In this contribution, we report on a class of emitters based on bridged oxo- and/or thioethers revealing striking photoluminescence properties in fluid solution and in the solid state. In total, nine compounds were investigated concerning their photophysical properties, which were interpreted by quantum chemical calculations. To our delight, we discovered compounds possessing nearly identical photoluminescence quantum yields (Φ_F ) in solution and in the solid state, which has been rarely reported so far. Besides these efforts, we shed light on the influence of polymorphism and solvent polarity on the emission properties. In addition, an in-depth X-ray diffractometric analysis was conducted to correlate molecular packing in the crystal with differences in the photophysical properties.

Keywords: Aromatics; Bridged ethers; Luminophores; Solution and solid-state emitter (SSSE).

Scheme 1

Molecular structures of the target compounds investigated in this contribution.

Figure 1

Photographs of the compounds dissolved in DMF and as powders along with the corresponding wavelength of the emission maxima. λ_ex=365 nm, concentration in DMF=50 μM. Photographs of compounds in DMF were performed above room temperature (60 °C) due to the low solubility in common organic solvents.

Figure 2

A) Photoluminescence spectra of the two polymorphs as single crystals. B) Fluorescence microscopy image of the red polymorph of compound S₂O₂‐e (B). C) Fluorescence microscopy image of the yellow polymorph of compound S₂O₂‐e (A). D) Fluorescence microscopy image of both polymorphs grown together from a saturated DMF solution. (λ _ex=365 nm).

Figure 3

Molecular structures and packing of compounds S₂O₂‐e (A) (yellow polymorph, CCDC 1913837) and S₂O₂‐e (B) (red polymorph, CCDC 1913838) as obtained by X‐ray diffractometric analyses.