Heating and mechanical force-induced luminescence on–off switching of arylamine derivatives with highly distorted structures

Abstract

A triphenylamine-based organic luminophor (TPA-CO) with a highly distorted structure has been designed and effortlessly obtained by an Ullmann reaction. The luminophor exhibits a stimuli-induced emission enhancement effect and intramolecular charge transfer properties. The fluorescence efficiency of its crystals is dramatically increased from 0.4% to 12.3% upon grinding. The emission enhancement is also realized by a heating process. The "bright" state can recover its original state and turn "dark". The luminescence "on-off" behaviour is repeatedly transformed by a grinding-vapour process or by a heating process. The XRD patterns of the "bright" and "dark" states show that the change of emission intensity is related to the reversible transition between the crystalline state and the metastable amorphous state. At the molecular level, the emission enhancement upon external stimuli may be attributed to conformational planarization and weak intermolecular interactions.

High-contrast and reversible mechanochromic luminescence of a D–π–A compound with a twisted molecular conformation

“…Similar phenomena of incomplete conversion have been observed in other ML systems. 17 Annealing or vapour fuming of the ground power results in the disappearance of the diffuse halo and the intensification of diffraction peaks, indicating the recovery of original crystalline state. From the PXRD results, it can be concluded that the conversion between crystalline and amorphous states is responsible for the reversible mechanochromism of TPAANDCV.…”

Highly Twisted Isomers of Triphenylacrylonitrile Derivatives with High Emission Efficiency and Mechanochromic Behavior

“…Chemicals and Instruments 1 HNMR and 13 CNMR spectra of the products were recorded on aB ruker AVANCE III 500-MHz instrument (Bruker,S witzerland) with tetramethylsilane (TMS) as the internal standard and chloroform-d (CDCl 3 )ast he solvent, which were purchased from Alfa Aesar.M ass spectrometry (MS) was performed with aT hermo DECAX-60000 LCQ Deca XF (Thermo, USA) mass spectrometer.F luorescence measurements were recorded on aH itachi F-4600 spectrophotometer.T he UV/Vis spectra were recorded with aU V-1800 UV/Vis spectrophotometer (Shimadzu, Japan). Photoluminescence (PL) quantum yields (F f )int he solid state were measured with aHamamatsu absolute PL quantum yield spectrometer C11347 (Quantaurus-QY,J apan).…”

“…1 HNMR (500 MHz,CDCl 3 ) d = 8.35 (s, 1H), 8.19 (d,J = 8.0 Hz,1H),7.62 (m,7H),3H),7.46 (dd,J = 9.0,6H),7.39 (d,J = 8.5 Hz,2H),2H),2H), (m, 2H),7.14-7.10 ppm (m, 2H). 13 CNMR (500 Hz, CDCl 3 ): d = 157. 4, 141.9, 141.5, 140.7, 139.4, 137.6, 133.0, 132.2, 130.8, 130.2, 130.0, 129.0, 128.8, 128.5, 128.4, 127.6, 127.1, 126.3, 125.2, 123.5, 120.4, 120.2, 118.7, 111.6, 110.1, 110.0 Crystallographic data for TPAN-C3:C 39 H 27 N 2 ,C 39 H 27 N 2 ,M = 522.62 gmol À1 ,T riclinic, a = 9.818(3), b = 12.379 (12) , c = 13.079 (13) ; b = 69.174(16) , V = 1437(2) 3, T = 293(2) K, R(int) = 0.0367, space group P À1 , D cal = 1.208 gcm…”

“…In addition, our group reported an ovel TPAN derivative, whichf ormed polymorphic crystals exhibiting luminescence switching upon exposure to solventv apour,m echanical, and thermalstimuli. [13] Herein, we preparet wo TPAN isomers, namely TPAN-C2 and TPAN-C3 as depicted in Scheme1,which exhibit ahighly twistTwon ovel triphenylacrylonitrile derivatives (TPAN-C2 and TPAN-C3)w ith highly twisted conformations have been successfully prepared by Suzuki coupling reaction. Both of them show mechanochromic (MC) fluorescent behaviour and exhibit remarkable fluorescencer edshifts from sky-blue to light green upon fully grinding them.…”

From Tetraphenylfurans to Ring‐Opened (Z)‐1,4‐Enediones: ACQ Fluorophores versus AIEgens with Distinct Responses to Mechanical Force and Light

“…Thus, the crystalline states of these luminogens may adopt a more twisted conformation and thus excited energy is partially consumed by nonradiative transitions. Upon grinding, the molecular structures become slightly more planar and the effective intramolecular conjugation increases, which further blocks the nonradiative deactivation pathways . Also, the neighboring molecules do not get close to one another due to the steric effect of the substituents, which weakens the intermolecular interactions.…”