Multi‐Stimuli‐Induced Mechanical Bending and Reversible Fluorescence Switching in a Single Organic Crystal

Abstract

Fluorescent single crystals that respond to multiple external stimuli are of great interest in molecular machines, sensors, and displays. The integration of photo-or acidinduced fluorescence enhancement and bending in one organic crystal, however, has not been reported yet. Herein, we report the interesting plastic photomechanical bending and switching on of the fluorescence of an azine crystal in a single-crystal transformation, due to extended p-conjugation and molecular slippage. Moreover, the fluorescent plastic bending driven by multiple volatile acid vapors was firstly observed, and attributed to the synergistic effect of push-pull electronic structure and hydrogen bonding. The single crystal also shows high elasticity under external force. In addition, reversible fluorescence switching can be triggered by grinding and solvent fuming, as well as by the adsorption and desorption of HCl vapor. The integration of plastic, elastic bending and switch-on fluorescence into one single crystal provides a new strategy for next-generation smart materials.

A Red-Emitting Cu(I)–Halide Cluster Phosphor with Near-Unity Photoluminescence Efficiency for High-Power wLED Applications

“…typically observed at low temperature, which is attributed to a 3 (M+X)LCT excited state [2,4,5,15,18]. However, the high-energy emission is not observed even at the lowest temperature (79 K) in this case.…”

“…A low-energy emission, i.e., λ em > 550 nm, which is assigned to the cluster-centered ( 3 CC) excited state can be observed for systems with intermetallic interactions and is independent of the nature of the ligands. In addition, a high-energy emission, i.e., λ em < 450 nm, is typically observed at low temperature, which is attributed to a 3 (M+X)LCT excited state [ 2 , 4 , 5 , 15 , 18 ]. However, the high-energy emission is not observed even at the lowest temperature (79 K) in this case.…”

“…Highly luminescent molecules or clusters have attracted much attention in the past two decades because of their wide applications in fields of display, sensing, light-emitting devices, etc. [1][2][3][4][5][6]. The photophysical properties of metal complexes can be modified not only by the property of central metals but also by organic ligands and metal-ligand interactions [7][8][9][10][11][12][13][14][15][16][17].…”

Designing Dual Mechanical Response in Molecular Crystals through Cocrystallization

“…25 The reported materials typically respond mechanically to only one external stimulus. Only a few examples of molecular 26,27 and coordination polymer crystals 7 31 To gain structural insights into the elastic bending behavior, the crystal structures of 1 and 2 were solved by single-crystal X-ray diffraction (SCXRD). Cocrystal 1 crystallizes in monoclinic space group P2 1 /c with one of each coformer (NVP and CBA) in the asymmetric unit (Table S2.1).…”

“…The reported materials typically respond mechanically to only one external stimulus. Only a few examples of molecular , and coordination polymer crystals have so far been shown to combine multiple mechanical responses into a single material. These multifunctional materials open the door to designing advanced actuating materials that can absorb one type of energy and convert it into a mechanical response.…”