Ya‐Hang Wu, Hongyan Xiao, Bin Chen
Feb 3, 2020
Citations
0
Influential Citations
25
Citations
Journal
Angewandte Chemie
Abstract
Contrary to Kasha's rule , three rigid and structurally-simple heterocyclic stilbene derivatives, (E)-3H, 3'H-[1,1'-biisobenzofuranylidene]-3,3'-dione (SDPE-OO), (E)-3-(3-oxobenzo[c] thiophen-1(3H)-ylidene)isobenzofuran-1(3H)-one (SDPE-OS), and (E)-3H,3'H-[1,1'-bibenzo[c] thiophenylidene]-3,3'-dione (SDPE-SS), are found to fluoresce in their neat solid phases, from upper (S 2 ) and lowest (S 1 ) singlet excited states, even at room temperature in air. Photophysical studies, single-crystal structure analyses and theoretical calculations indicate that large energy gaps between S 2 and S 1 states (T 2 and T 1 states) as well as an abundance of intramolecular and intermolecular hydrogen bonds suppress internal conversions of the upper excited states in the solids and make possible the occurrence of fluorescence from S 2 excited state (phosphorescence from T 2 excited state). These results, including unprecedented fluorescence quantum yields (2.3-9.6%) from the S 2 states in the neat solids, establish a unique molecular skeleton for achieving multi-colored emissions from upper excited states by 'suppressing' Kasha's rule.