Nonaxisymmetrical 9,10-diarylanthracenes: Separable swivel conformers and promising optoelectronic properties

The chemical and physical functions of organic molecules are closely related to their conformations in both solutions and solid states, but the successful separation of organic conformers is usually very difficult because of the rapid internal rotation of single bonds. In the current work, we first demonstrate two stable and separable conformers with swivel cross-conjugated configuration based on 9,10-diphenylanthracene derivatives, and they are confirmed by 1H NMR spectra and single crystal analysis. The introduction of two bulky groups at the ortho positions of the two phenyls can enhance the internal rotation barrier of phenyl–anthryl single bond to fully stabilize the conformers in respective conformation even in reflux toluene. We find that they show similar solution but very different solid-state optical properties such as different emission wavelength and fluorescence efficiency. Moreover, only the syn conformer crystal can exhibit mechanochromic luminescence and mechanoluminescence.