Issue 30, 2022, Issue in Progress

AIE and reversible mechanofluorochromism characteristics of new imidazole-based donor–π–acceptor dyes

Abstract

Four new imidazole-based donor–π–acceptor 2a–2d dyes have been synthesized, and their solvatochromism, aggregation-induced emission (AIE) and mechanofluorochromic (MFC) properties were investigated. The new dyes 2a–2d were designed to have 1,4,5-triphenyl-1H-imidazole as an electron donor (D) and 1-indanone, 1,3-indandione, 2-phenylacetonitrile and 2-thiopheneacetonitrile as electron acceptors (A) linked through a phenyl bridge. The maximum absorption wavelength of 2a–2d dyes in DCM solution appeared at 376, 437, 368, and 375 nm, respectively. The dyes exhibit a high molar extinction coefficient (ε) and large Stokes shift, making them useful in optoelectronic applications. Solvatochromic properties of dyes 2a–2d have been studied and showed bathochromic changes in emission wavelengths, from 449 to 550 nm for 2a, 476 to 599 nm for 2b, 438 to 520 nm for 2c, and from 439 to 529 nm for 2d, as the solvent polarity increased from n-hexane to acetonitrile. Moreover, in dioxane/water mixture systems, AIE behaviors were observed, and the emission intensity of 2b–2d dyes increased by around 5, 3, and 3 times in the mixed solvent (dioxane : water = 10 : 90) in contrast to pure dioxane. In addition, the XRD data of the 2a–2d dyes in pristine, ground, and fumed states illustrate that the transition between the ordered crystalline and disordered amorphous phases is the primary cause of MFC behaviors mechanism. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) showed that the highest occupied molecular orbital (HOMO) of dyes is distributed on the donor unit. In contrast, the lowest unoccupied molecular orbital (LUMO) is mainly placed on the acceptor unit to reveal that the HOMO–LUMO transition has a great ICT character.

Graphical abstract: AIE and reversible mechanofluorochromism characteristics of new imidazole-based donor–π–acceptor dyes

Supplementary files

Article information

Article type
Paper
Submitted
05 Mar 2022
Accepted
21 Jun 2022
First published
01 Jul 2022
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2022,12, 19270-19283

AIE and reversible mechanofluorochromism characteristics of new imidazole-based donor–π–acceptor dyes

O. F. Al Sharif, L. M. Nhari, R. M. El-Shishtawy, M. E. M. Zayed and A. M. Asiri, RSC Adv., 2022, 12, 19270 DOI: 10.1039/D2RA01466A

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