An iminodibenzyl-quinoxaline-iminodibenzyl scaffold as a mechanochromic and dual emitter: donor and bridge effects on optical properties

The influence of phenyl linkage and donor strength on the photophysical properties of new derivatives of quinoxaline-containing iminodibenzyl and iminostilbene moieties is studied. The donor-acceptor derivatives showed dual thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) despite a large energy gap between the excited singlet and triplet states ( ca. 0.5 eV). This extremely rare observation is explained by the twisted and rigidified structure of the iminodibenzyl moiety. Dual emission (TADF + RTP) and mechanochromism have been obtained using an iminodibenzyl-quinoxaline-iminodibenzyl scaffold.