Impact of Electron-Donating Groups on Attaining Dual-Emitting Imidazole-Based Donor–Acceptor Materials

Abstract

Imidazole-based donor–acceptor materials are well known for their polarity-controlled trade-off phenomenon between the localized excitation-based short-wavelength (SW) emission in nonpolar solvents and charge transfer dominated long-wavelength (LW) emission in polar solvents. To attain concurrent SW- and LW-based dual-emission characteristics, a series of imidazole-based donor–acceptor fluorophores (CBImDCN, TPImDCN, PZImDCN) possessing different electron-donating groups such as carbazole, triphenylamine, and phenothiazine linked via the N-position of the imidazole core unit were synthesized and verified by NMR and mass spectroscopic techniques. As a result, the strong donating TPImDCN and PZImDCN exhibited dual emission in different solvents of varying polarity, covering the blue (SW) and green/orange (LW) regions. On the other hand, in contrast, only an SW emission band is observed with the weak donating CBImDCN. Moreover, PZImDCN shows panchromatic emission under 365 nm illumination, while only orange color emission is observed under visible light excitation, revealing two different origins of SW and LW emissions, as also evidenced from DFT calculations. Overall, this work reveals a new approach for attaining concurrent SW and LW emission characteristics from imidazole-based D–A materials and sheds light on the design and development of novel panchromatic emitters with intriguing properties for lighting and display applications.

Arylacetylene End-Capped Triarylamine-Based D–A System for Switching from Binary to Ternary Memory Behavior

“…The additional peak, at 489 nm, originated from the charge transfer between highly electron-donating triarylamine and the electron-accepting −CF 3 unit. 33,34 The experimental and computational absorption and emission wavelength values agree significantly agree. The results are given in Table 1.…”

“…The peak at 448 nm corresponds to the locally excited emission contributed by the π–π* transition that arises from the phenanthroimidazole. The additional peak, at 489 nm, originated from the charge transfer between highly electron-donating triarylamine and the electron-accepting −CF 3 unit. , The experimental and computational absorption and emission wavelength values agree significantly agree. The results are given in Table .…”

Synthesis, photophysics and two-photon absorption of imidazole-centred tripodal chromophores

“…The expected nonplanar arrangement of the central triphenylimidazole corresponds to the related X-ray molecular structures. 39,40,48 For instance, N-ethyllophine (CCDC 765921) and 1a showed a similar nonplanar arrangement of the phenyls appended at the imidazole C2/C4/C5 (torsion angles 41/18/71 vs. 27/21/551). With tricarbaldehyde 1a in hand, we further extended our investigation to series b (Scheme 2).…”

“…Imidazole-centred tripodal molecules have found various applications as pharmacophores, 36 charge-transfer (CT) chromophores, 37 fluorophores, [38][39][40][41][42] molecular sensors capable of detecting various analytes such as F À , BF 4 À /ClO 4 À , Hg 2+ , Zn 2+ , cysteine or picric acid, [43][44][45][46][47][48][49][50][51] viscosity probes, 52 pH probes, 53,54 luminescent solar concentrators (LSCs), 55 emitters for organic light-emitting diodes (OLEDs) [56][57][58][59] and robust heterocycles for dye-sensitised solar cells (DSSCs). [60][61][62] Besides interesting linear optical properties, imidazole push-pull molecules have also been investigated for their nonlinear optical (NLO) activity.…”

Odd–Even Effect in Charge Transfer Complexes through the Regulation of the Alkyl Chain

“…Dual emissions have been shown to be a viable way to realize white light emission. ,− It was interesting that TAT-5C@TCNPh exhibited a white light under 312 nm UV irradiation, and the corresponding CIE chromaticity coordinates were calculated to be (0.32, 0.36) (Figure d and Figure S32a). This white light emission resulted from the dual emissions of the blue fluorescence from TAT-5C and the yellow TADF from the CT complex.…”