Pyranone–Arylbenzene Molecules Controlled by the Competition of Local Excited State and Twisted Intramolecular Charge-Transfer State: Dual-State Emission, Polymorphism, and Mechanofluorochromism

Abstract

The adjustment of the luminescent properties of materials according to different environments has always been a hot topic. Among them, the local excited (LE) state and the twisted intramolecular charge-transfer (TICT) state are important factors that affect the photophysical properties of compounds. Herein, four donor–acceptor pyranone–arylbenzene molecules were synthesized using pyranone (Pr) as the acceptor and phenyl (Ph), naphthalene (Np), anthracene (An), and pyrene (Py) as donors, respectively. The results of experiments and theoretical calculations show that the TICT state dominates the luminescent properties of Pr–Ph and Pr–Np, which results in fluorescence quenching in solution and solid states. However, Pr–An and Pr–Py are dominated by the LE state caused by rigid anthracene and pyrene, and the twisted molecular conformations avoid the strong π–π interactions, leading to dual-state emissions. Moreover, Pr–An has two completely different polymorphs, Pr–An-SB and Pr–An-YG, which emit sky-blue and yellow-green fluorescence due to different conformations and stacking arrangements, respectively. Both the polymorphs can be transformed into an amorphous state that emits dark cyan fluorescence upon grinding, revealing high-contrast mechanofluorochromic properties. Furthermore, Pr–An-YG can be converted into more stable Pr–An-SB by solvent fumigation, revealing vapochromic activity. This work provides some useful information for the development of fluorescent materials based on LE and TICT states.

Mechanofluorochromism of (D–π–)2A-type azine-based fluorescent dyes

“…In particular, the intermolecular MFC (inter-MFC) based on reversible changes in molecular orientation and arrangement of dye molecules is superior in durability to the intramolecular MFC (intra-MFC) based on reversible changes in the chemical structures of dye molecules by cleavage and reconstruction of chemical bonds during the grinding–heating process, and thus, the inter-MFC is expected to be applicable to rewritable photoimaging and electroluminescence devices. 8–70 Among various types of fluorescent dyes possessing the mechanofluorochromic properties, donor–π–acceptor (D–π–A)-type fluorescent dyes composed of an electron-donating moiety (D) and an electron-withdrawing moiety (A) connected by a π-conjugated bridge exhibit intense photoabsorption and fluorescence emission properties based on the intramolecular charge transfer (ICT) excitation from the D moiety to the A moiety. 11–33 Thus, the dipole moments as well as photoabsorption ( i.e.…”

“…8–70 Among various types of fluorescent dyes possessing the mechanofluorochromic properties, donor–π–acceptor (D–π–A)-type fluorescent dyes composed of an electron-donating moiety (D) and an electron-withdrawing moiety (A) connected by a π-conjugated bridge exhibit intense photoabsorption and fluorescence emission properties based on the intramolecular charge transfer (ICT) excitation from the D moiety to the A moiety. 11–33 Thus, the dipole moments as well as photoabsorption ( i.e. , color) and fluorescence emission ( i.e.…”

D–A–D structured triphenylamine fluorophore with bright dual-state emission for reversible mechanofluorochromism and trace water detection

“…Fluorescent materials with high emission efficiency have attracted great attention due to their potential in applications such as chemo-/biosensors, mechanosensors, bioimaging, and organic light-emitting diodes (OLEDs). [1][2][3][4][5][6][7][8] The reported fluorescent materials mainly focus on aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) molecules. [9][10][11][12] Although ACQ molecules are highly emissive in dilute solutions, they are non-emissive or show weak emission in the solid state due to the nonradiative decay caused by the formation of detrimental aggregates.…”

CF3 H-bonding locked aromatic stacking of picric acid with mechanofluorochromic fluorophores: highly selective reusable sensor and rewritable fluorescence platform

“…16,17 Tailoring the fluorophore structure is one important tool employed for deriving desirable/unexpected functional properties in the resulting fluorescent materials. 18 Integrating alkyl chain functionality to control molecular packing has resulted in self-reversible mechanofluorochromic, liquid crystalline and room-temperature phosphorescent materials. [19][20][21][22][23] Tunable fluorescence materials have been obtained by changing donor and acceptor functionality.…”