Synthesis and luminescence properties of substituted benzils.

Yasui, Masamichi; Fujihara, Takashi; Ohtsu, Hiroyoshi; Wada, Yuki; Shimada, Terumasa; Zhu, Yiying; Kawano, Masaki; Hanaya, Kengo; Sugai, Takeshi; Higashibayashi, Shuhei

Photophysical properties of benzil (1,2-diphenylethane-1,2-dione) and its derivatives in the crystal state have recently attracted much attention. However, the study of substituted benzils has mostly been limited to para-substituted derivatives, which did not induce a significant effect on the emission wavelength compared to pristine benzil. The effects of ortho- and meta-substituents on the photophysical properties in the crystal state have not been investigated so far. Our recently developed organocatalytic pinacol coupling of substituted benzaldehydes allowed us to prepare various ortho-, meta-, and para-substituted benzil derivatives and to investigate their luminescence properties. Ortho- and meta-substituents affected the electronic states of benzils in the crystal state, resulting in differences in their luminescence properties. The luminescence wavelength and type, i.e., phosphorescence or fluorescence, were altered by these substituents. Fast self-recovering phosphorescence-to-phosphorescence mechanochromism by the para-CF3 substituent at room temperature was also discovered. Benzil and its derivatives have been widely studied for their luminescence properties, but the effects of ortho- and meta-substituents on photophysical properties have yet to be explored. Here, ortho-, meta- and para-substituted benzil derivatives are accessed via an organocatalytic pinacol coupling of substituted benzaldehydes, and ortho- and meta-substituents are shown to significantly influence the electronic state and luminescence properties of benzil.

BENZIL; WAVELENGTHS; FLUORESCENCE; CRYSTALS; LUMINESCENCE; PHOSPHORESCENCE

Communications Chemistry, 2023, Vol 6, Issue 1, p1

2399-3669

Academic Journal

10.1038/s42004-023-01038-6