Constructing Full-Color Highly Emissive Organic Solids Based on an X-Shaped Tetrasubstituted Benzene Skeleton

With the aim of highlighting the potential talent of the unique single-benzene skeleton versus the common large pi-systems, we propose a general strategy to construct single-benzene fluorophores 1-9, featuring fascinating emission properties in the solid state, for example, high fluorescence quantum yields and wide variety of emission colors. Our molecular design is X-shaped tetrasubstituted benzene of which two electron-donating groups (EDGs) and two electron withdrawing groups are arranged in an X-shaped fashion. This molecular design enables a very small single-benzene skeleton to show intense fluorescence in the solid state because the pi-pi stacking and dipole-dipole interaction are inherently avoided in the crystal. More importantly, by simply changing the EDGs, the emission colors in the solid state of these single-benzene fluorophores can be continuously tuned from deep blue to red. In addition, the potential applications of these single-benzene fluorophores as crystal lasing media have been demonstrated by an amplified spontaneous emission measurement.