Crystallization‐Induced Emission Enhancement of a Deep‐Blue Luminescence Material with Tunable Mechano‐ and Thermochromism

Abstract

Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli‐responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine‐based spacer. This amide‐rich molecule offers many possibilities for forming intra‐ and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as‐prepared two‐component cocrystalline material displays an exceptive deep‐blue emission, which is extremely rare among naphthalimide‐based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual “turn off” thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid‐state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system.

Influence of Calcination Temperature on Crystal Growth and Optical Characteristics of Eu3+ Doped ZnO/Zn2SiO4 Composites Fabricated via Simple Thermal Treatment Method

“…Luminescent materials such as phosphors are the substances that emit light in the electromagnetic waves (EM) spectrum after the conversion of the absorbed energy from an energy source. These materials may be classified according to the wide range of excitation energy sources and excitation trigger [2][3][4]. Essentially, photoluminescence is a phenomenon where the emission of light happens when stimulated by short-wavelength light, usually ultraviolet (UV) light or visible light [5].…”

Stimuli‐Responsive AIEgens

“…[ 75 ] Therefore, a myriad of AIEgens with diverse stimuli‐responsive properties has been developed in recent years, and the resulting materials have shown broad application prospects. [ 76–96 ]…”

Naphthalimide‐Based Hydrazone Derivatives: Synthesis, Mechanochromism in the Solid State and Response to Ions in Dilute Solutions

“…Some reports have shown that 1,8‐naphthalimide hydrazone‐conjugated organic compounds with planar structures and an electron‐donating group, are able to increase fluorescence quantum yields and tune the emission wavelength to longer regions [9] . Stimuli‐responsive dyes with two naphthalimide chromophores have been reported, and offer a good many of intra‐ and intermolecular hydrogen bond interactions and exhibit an apparent mechanochromic fluorescent behavior, which is extremely rare among naphthalimide‐based molecules in the solid state [10] . Previous work has shown that mechanical forces can induce the morphology change through enhancing π‐π stacking and destroying hydrogen bonds and twisted molecular conformation and the absence of intermolecular interaction lead to a loose packing mode, [11] and the transformation of molecular packing accounts for the obvious mechanofluorochromic effect [12] …”