Multistimuli-Responsive Squaraine Dyad Exhibiting Concentration-Controlled Vapochromic Luminescence

Abstract

Stimuli-responsive organic materials with controllable luminescence are of enormous importance because of their potential applications in sensing, data security, and display devices. In this study, a multistimuliresponsive squaraine dyad (SQ-d) composed of two rigid squaraine moieties and a flexible ethylene linker was rationally designed and synthesized. SQ-d exhibits polymorphic luminescence, which can be reversibly switched by various external stimuli, including solvent vapor exposure, heat, and shear force. Unexpectedly, the weakly luminescent phase (O1) of SQ-d exhibits concentration-controlled vapochromic behavior. Film O1 can convert to a highly green-emissive phase (G1) under a low concentration of CHCl 3 vapor and convert to a highly yellow-emissive phase (Y) under a high concentration of CHCl 3 vapor; these originate from two distinct crystallization-induced emission enhancement processes. To the best of our knowledge, this is the first investigation of the effect of vapor concentration on the phase transitions of organic vapochromic luminophores. By analyzing the single-crystal structures and photophysical properties of SQ-d, we concluded that the green and yellow emissions probably originated from a zigzag stacking mode and an H-type π−π stacking mode, respectively. Finally, two prototypes based on SQ-d for applications in information encryption and vapor sensing were successfully demonstrated.

Stimuli‐Responsive Properties on a Bisbenzofuropyrazine Core: Mechanochromism and Concentration‐Controlled Vapochromism

“…Moreover, when samples in the green luminescent states (concentration of CHCl 3 vapor=1029–1092 mg/L) were exposed to air, they quickly changed to blue luminescence, same as observed at lower concentrations. Such a rapid color change in responsive to the vapor concentration is highly suggestive of multi‐step phase transition, which is not trivial in the literature [8] …”

“…Recently, Yang and coworkers reported two types of luminescence switching through a two‐step phase transition, taking advantage of the difference in the phase transition speed [7] . Yang, Jiang, and coworkers also achieved luminescence switching depending on solvent vapor concentration to induce phase transitions [8] . Despite these certain advancements, luminescence switching by solvent vapor concentration still remains underdeveloped [9]…”

Vapochromism of indolenine-based heptamethine cyanine dye adsorbed on silica gel

“…Interestingly, the TLC plates adsorbed with HMCD 3 changed from bluegreen to pale blue-green upon exposure to the vapors of various chlorinated solvents, such as CH 2 Cl 2 , CHCl 3 , CH 2 ClCH 2 Cl, and PhCl. 14 After exposure to chlorinated solvents, the original blue-green was restored when the plates were left in air.…”

Multistimuli-responsive behavior of a phosphorescent Cu3pyrazolate3complex for luminescent logic gates and encrypted information transformation

“…[1][2][3][4][5][6][7][8][9][10] Stimuli-responsive luminescence behavior involves several fundamental scientific aspects, and the most essential one may be the effect of different external stimuli on the luminescence properties by changing the intermolecular interactions (e.g., hydrogen-bonds and π⋯π interactions) and the relevant aggregation of this type of material. [1][2][3][4]7,8,[11][12][13][14] A series of relevant advanced applications have also been demonstrated in the literature, including diagnosis, 2,6,13,14 optoelectronic noses, 5,8 anticounterfeiting technology, 15,16 confidential data encryption, 17,18 and molecular logic gates. [19][20][21] To date, in order to better meet the complicated requirements of real-world applications, the focus of development of stimuli-responsive materials has been transferring to multi-responsive luminescent materials although they remain much less investigated relative to the mono-responsive ones.…”