Bending-Induced Fluorescence Shift of Dual-Shaped Flexible Organic Crystals from a Diaminoterephthalate with Nonplanar Conformation

The integrationof bending-induced fluorescence shifts (BIFS)and outstanding elasticity across a wide temperature range into thestraight-shaped (Cry-S) and naturally curved (Cry-NC) crystals froma diaminoterephthalate with the nonplanar conformation. The development of flexible crystalline materials witha bending-inducedfluorescence shift (BIFS) remains a challenge. The flexible crystalswith BIFS properties reported so far are mainly realized by chemicalstructures with a planar conformation or a special donor-& pi;-acceptorconfiguration. Here, BIFS is simultaneously achieved in the straight-shaped(Cry-S) and naturally curved (Cry-NC) crystal prepared by a halogenateddiaminoterephthalate derivative with a nonplanar conformation. Cry-Sdisplays an obviously reversible red-shifted fluorescence (& SIM;20nm) in the bent position compared with its original (undeformed) state.In contrast to the naturally curved position (undeformed), Cry-NCsimilarly shows a red shift (& SIM;16 nm) at its acutely bent position(deformed). In addition, Cry-S and Cry-NC can be reversibly bent ina wide temperature range from - 6 to 180 & DEG;C under mechanicalexternal force. It is hoped that this work would facilitate the designof BIFS materials and their applications in the field of mechanicallystimulated light sensors.