A Bendable Photoluminescent Molecular Crystal with Phase Transition Accompanied by SHG Switching

Abstract

Phase transition materials, which enable the switching of physical properties like second harmonic generation (SHG), have attracted great interest due to their wide applications, such as in sensors. However, although significant progress has been made in crystalline SHG switching phase transition materials, these materials typically show poor mechanical flexibility, hindering their applications in flexible wearable devices. Herein, for the first time, we reported a bendable photoluminescent molecular crystal (R)-octan-2-yl(E)-4- ((4-(hexadecyloxy)-2-hydroxybenzylidene)amino)benzoate (R-EHAB), which shows a phase transition at around 320 K, accompanied by obvious SHG switching between high-SHG and low-SHG states. Significantly, R-EHAB demonstrates a low elastic modulus of 3.03 GPa, which is much lower than that of most molecular phase transition crystals. This enables its crystals to be easily bent into a semicircular shape and remain unchanged after bending-recovery cycles. To our knowledge, R-EHAB is the first bendable molecular crystal with a phase transition accompanied by SHG switching. This work would inspire the further exploration of more bendable phase transition crystals for potential application in next-generation functional devices.

Keywords

SHG switching / Phase transition / Bendability / Photoluminescence / Molecular crystal / Elastic modulus / Schiff base / Chirality / Mechanical properties / Materials science

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