Multicolored‐Fluorescence Switching of ICT‐Type Organic Solids with Clear Color Difference: Mechanically Controlled Excited State

Abstract

A donor-acceptor-type fluorophore containing a twisted diphenylacrylonitrile and triphenylamine has been developed by using the Suzuki reaction. The system indicates typical intramolecular charge-transfer properties. Upon mechanical grinding or hydrostatic pressure, the fluorophore reveals a multicolored fluorescence switching. Interestingly, a fluorescence color transition from green to red was clearly observed, and the change of photoluminescent (PL) wavelength gets close to 111 nm. The mechanisms of high-contrast mechanochromic behavior are fully investigated by techniques including powder XRD, PL lifetime, high-pressure PL lifetime, and Raman spectra analysis. The tremendous PL wavelength shift is attributed to gradual transition of excited states from the local excited state to the charge-transfer state.

Branched triphenylamine-core compounds: aggregation induced two-photon absorption

“…2a. We can see that T1 shows two absorption peaks in ethanol which located at ~293 nm and ~441 nm. The fluorescence intensity primarily decreased and the emission peak red shifted slightly with increasing f w when fw≤ 50%, which could be attributed to the twisted intramolecular charge-transfer (TICT) 30, 31, then the fluorescence intensity increased and the emission peak showed remarkable red-shift with the f w increasing when f w ≥50%, which could be ascribed to the formation of a charge-transfer (CT) excited 32,33 and the formation of J-aggregation. Moreover, the two absorption peaks of T1, T2 both red shift with the increasing of f w , which is the feature of the J-aggregation 29 .…”

Mechanochromic Luminescence of Aggregation-Induced Emission Luminogens

“…Ma and coworkers developed a donor-acceptor-type MC luminogen containing twisted diphenylacrylonitrile and triphenylamine units. 54 The luminogen reveals a multi-color fluorescence switching upon mechanical grinding or applying a hydrostatic pressure due to the alteration of two different excited states. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”

Mechanothermally induced conformational switch of a porphyrin dimer in a polymer film

“…6 In addition, fluorophores in which a multicolor switch could be induced by mechanical force via the synergistic effect of intramolecular conformational twisting and intermolecular molecular packing modes were recently reported. 7 Notably, the photophysical properties of 9,10-bis(phenylethynyl)anthracene and several poly(phenyleneethynylene)s were investigated in regard to the aggregation-induced coplanarization of the twisted species in solution and thin films. 8 However, the conformational changes between twisted and planar forms were not attributed to the stretching of the films.…”