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• W3127681921 abstract "Open AccessCCS ChemistryRESEARCH ARTICLE1 Feb 2022Thermally Activated Delayed Fluorescence of Aggregates Induced by Strong π–π Interactions and Reversible Dual-Responsive Luminescence Switching Xiangyu Zhang, Tong Lu, Changjiang Zhou, Haichao Liu, Yating Wen, Yue Shen, Bao Li, Shi-Tong Zhang and Bing Yang Xiangyu Zhang State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Tong Lu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Changjiang Zhou Shenzhen Key Laboratory of Polymer Science and Technology, College of Materials Science and Engineering, Shenzhen University, Shenzhen 518060 Google Scholar More articles by this author , Haichao Liu *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Yating Wen State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Yue Shen State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Bao Li State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author , Shi-Tong Zhang State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author and Bing Yang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 Google Scholar More articles by this author https://doi.org/10.31635/ccschem.021.202000731 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail A reversible dual-responsive luminescent material was introduced by our group to show the simultaneous color and lifetime switching in response to external stimuli. Pristine crystalline powder of (E)-2-(benzo[d]thiazol-2-yl)-3-(pyren-1-yl)acrylonitrile (Py-BZTCN) shows the ordered π–π stacking with only near-monomer-normal orange-yellow fluorescence, but it exhibits red emission with thermally activated delayed fluorescence (TADF) after grinding, which can be reversibly recovered by heating or fuming treatment. Grinding disturbs the ordered π–π stacking of pristine powder, leading to the formation of small aggregates with compressed distance and increased overlap of π–π stacking between adjacent molecules. The cause of switching was verified by single-crystal X-ray diffraction experiments of two corresponding crystals. This strong π–π interaction effectively promotes the excited-state energy splitting and substantially decreases the singlet–triplet energy gap (ΔEST) of aggregates, resulting in the red TADF emission of aggregates through reverse intersystem crossing. This finding proposes a new route to realizing the TADF emission of aggregates through strong intermolecular interactions based on non-TADF monomer, thereby enabling a novel high-contrast dual-responsive luminescence switching. Download figure Download PowerPoint Introduction Organic π-conjugated materials attract extensive attention in stimuli-responsive luminescence switching studies because their luminescence characteristics (e.g., color, intensity, and lifetime) can be easily tuned by molecular structure and molecular packing.1,2 Meanwhile, thermally activated delayed fluorescence (TADF) materials have become an important member in the extended family of stimulus responses as a result of their special delayed lifetime between fluorescence and phosphorescence.3–7 With regard to the TADF mechanism, a nearly degenerate energy (a very small energy difference, ΔEST) exists between the lowest excited singlet (S1) and triplet (T1) states, enabling the occurrence of reverse intersystem crossing (RISC) from triplet to singlet states and resulting in delayed fluorescence with the aid of thermal energy.8,9 Since the first purely organic TADF material was discovered in 1961,10 TADF material has been continuously developed, and recently Adachi and latter researchers11–28 have made important progress. Generally, the access to TADF includes several categories of molecular systems as follows: (1) fullerenes, whose TADF is primarily due to the highly delocalized π electrons over the whole sphere12; (2) some metal–organic complexes, which show TADF with a small ΔEST and a stable T1 arising from a metal-to-ligand charge-transfer (CT) excited state and relatively weak spin–orbit coupling;13,14 (3) pure organic donor–acceptor (D–A) molecules, which are typically featured with a large twist between D and A units by steric hindrance or a spiro-junction, as well as a small ΔEST through strong intramolecular CT state;15–18 (4) intermolecular D/A complexes, which acquire a small ΔEST from the exciplex state through space CT and are also an important TADF material system;15,19–21 (5) aggregation-induced delayed fluorescence (AIDF),22–25 which can be observed in the aggregate state owing to the greatly suppressed nonradiation through restricting intramolecular motions, making intersystem crossing (ISC) and RISC more competitive than nonradiative decay of S1; and (6) nitrogen- and boron-containing polycyclic aromatic compounds, in which the arrangement of nitrogen and boron atoms facilitates effective separation between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), leading to the minimized ΔEST and multi-resonance TADF with narrow emission.26–28 Different TADF systems and mechanisms have been proposed, but their intrinsic nature is dominated by the CT excited state and efficient HOMO–LUMO separation. In this contribution, based on the confirmed non-TADF of monomers, an unusual TADF of aggregates is discovered in one-dimensional close π–π stacking, arising from the reduced ΔEST by the excited-state energy splitting through strong π–π interactions and the aggregation of multiple molecules. Usually, the stimuli-responsive luminescence of organic solid-state material shows remarkable changes in emission color in response to external stimuli (e.g., grinding, heating, and fuming).8,9,29–45 However, simultaneous dual-responses of emission color and lifetime rarely occur between normal fluorescence and aggregate TADF. Herein, we report such a stimuli-responsive luminescence switching based on (E)-2-(benzo[d]thiazol-2-yl)-3-(pyren-1-yl)acrylonitrile (Py-BZTCN) molecule with pyrene (Py) as D and 2-(benzo[d]thiazol-2-yl)acrylonitrile (BZTCN) as A (Chart 1). Pristine crystalline powder showed a normal orange-yellow fluorescence emission, but this prompt fluorescence was switched into red TADF emission after grinding. This ground powder can be reversibly recovered to the initial orange-yellow emission by heating or fuming. Experimental and theoretical investigations demonstrated that such dual-responsive luminescence switching can be ascribed to a change in intermolecular interactions due to the different molecular packing.46–49 Crystals with orange-yellow emission (O-type for simplicity) showed long-range ordered π–π stacking with relatively weak intermolecular interaction, whose fluorescence was consistent with that of pristine powder. Grinding disturbance formed small aggregates with compressed π–π distance and increased π–π overlap between adjacent molecules, so the strong π–π interactions promoted the excited-state energy splitting to substantially reduce ΔEST, resulting in the occurrence of TADF. Most importantly, a red emitting (R-type for simplicity) crystal with TADF property was successfully grown, thereby providing solid and direct evidence for the red TADF emission through strong π–π interactions and the aggregation of multiple molecules. This novel case of grinding-induced TADF emission in π–π aggregates for dual-responsive luminescence switching can provide a new pathway to harvesting the TADF emission of aggregates through strong π–π interactions based on non-TADF monomers. Chart 1 | Molecular structures of TADF materials in this and previous works in this area. Download figure Download PowerPoint Experimental Methods Py-BZTCN was synthesized as follows: pyrene-1-carbaldehyde (806 mg, 3.5 mmol), benzothiazole-2-acetonitrile (727 mg, 4.2 mmol), and piperidine (3.2 mL, 35.0 mmol) were added to 30 mL ethanol. The mixture was allowed to react at room temperature for 8 h. After removing the solvent, the residue was dissolved in dichloromethane and concentrated in vacuum. It was purified by silica gel chromatography (eluent solvents: petroleum ether and dichloromethane) and then by sublimation to afford the orange-yellow powder in 89% yield (1070 mg). 2-(Pyren-1-yl)benzo[d]thiazole (Py-BZT) was synthesized as follows: a mixture of pyrene-1-carbaldehyde (465 mg, 2.0 mmol), 2-aminobenzenethiol (257 μL, 2.4 mmol), and dimethyl sulfoxide (DMSO) (15 mL) was degassed and recharged with nitrogen. After being stirred and refluxed at 170 °C for 12 h under nitrogen atmosphere, the mixture was cooled down to room temperature. Water (50 mL) was added, and the mixture was extracted with dichloromethane (3 × 150 mL). The organic phase was dried with anhydrous sodium sulfate, filtered and concentrated in vacuum. It was purified by silica gel chromatography (eluent solvents: petroleum ether and dichloromethane) to afford the light yellow powder in 33% yield (220 mg). Their structures were characterized by 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. The details are shown in the Supporting Information. 1H and 13C NMR spectra were recorded on a Bruker AVANCE 500 spectrometer (Bruker Corp., Switzerland), using tetramethylsilane (TMS) as the internal standard. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was carried out using an AXIMA-CFR™ plus instrument (Bruker Corp.). Elemental analysis was carried out by a FlashEA 1112, CHNS elemental analysis instrument (Elementar, Germany). Single-crystal X-ray diffraction (XRD) experiments were carried out on a Rigaku R-AXIS RAPID diffractometer equipped with a Mo-Kα and control software using the RAPID AUTO (Rigaku Corp., Japan). For R-type crystal of Py-BZTCN, the diffraction experiment was performed at the BL17B beamline, Shanghai Synchrotron Radiation Facility (SSRF). The crystal structures were solved with direct methods and refined with a full-matrix least-squares technique using the Olex2 program. Powder XRD patterns were collected on a Rigaku SmartLab(3) diffractometer (Rigaku Corp.). UV–vis spectra of solutions were recorded on a Shimadzu UV-3100 spectrophotometer (Shimadzu Corp., Japan). Steady-state photoluminescence (PL) spectra and time-resolved spectra were carried out by FLS980 fluorescence spectrometer (Edinburgh Instruments Ltd., United Kingdom). PL quantum yields (PLQYs) were measured using an integrating-sphere apparatus. Low-temperature fluorescence spectra were recorded by FLS980 fluorescence spectrometer and phosphorescence spectra were recorded by FluoroMax-4 spectrofluorometer (Horiba Jobin Yvon, France) with a Dewar flask. Thermal gravimetric analysis (TGA) was undertaken on a PerkinElmer thermal analysis system (TA Instruments, USA) at a heating rate of 10 °C min−1 and a nitrogen flow rate of 80 mL min−1. Differential scanning calorimetry (DSC) analysis was carried out using a NETZSCH (DSC-204) instrument (Netzsch Corp., Germany) at a heating rate of 10 °C min−1 in nitrogen flow. The ground-state potential energy curve was obtained on the basis of density functional theory (DFT) method at the level of B3LYP/6-31G(d,p). Optimized excited-state geometry, excited-state energy, and natural transition orbitals (NTOs) were calculated on the basis of time-dependent DFT (TD-DFT) method at the level of B3LYP/6-31G(d, p). All the DFT and TD-DFT calculations were carried out using the Gaussian 09 (version D.01) package. Results and Discussion Py-BZTCN compound was synthesized using the Knoevenagel reaction of pyrene-1-carbaldehyde and benzothiazole-2-acetonitrile ( Supporting Information Scheme S1),50 and purified by column chromatography and sublimation method, respectively. For comparison, the counterpart Py-BZT was synthesized according to a previous report ( Supporting Information Scheme S2).51 The 1H NMR spectrum of Py-BZTCN powder from column chromatography exhibited the mixture of cis- and trans-isomers, whereas powder purified by sublimation showed only the trans-isomer according to the 1H NMR spectrum and even the crystal structure (subsequent discussion) ( Supporting Information Figure S1). To compare the photophysical properties between cis- and trans-isomers, two kinds of powders were dissolved in diluted DMSO solvent in darkness, and then the PL spectra and lifetimes were measured. Two solutions presented the same PL spectrum (λmax = 559 nm) with a short lifetime (τ = 2.17 ns). Likewise, the DMSO solution of sublimated powder demonstrated an unchanged PL spectrum before and after UV irradiation despite the occurrence of cis → trans isomerism induced by UV irradiation according to the 1H NMR spectra ( Supporting Information Figure S2). Moreover, 5 wt % of two powders was dispersed in polymethyl methacrylate (PMMA) in darkness to prepare solid-state films to make the surroundings rigid, and the same PL spectrum and lifetime of two films remained ( Supporting Information Figure S3). These results indicated that cis- and trans-isomers had almost the same photophysical properties, so the pure trans-isomer powder was prepared by sublimation as our research object in this work. To further understand the excited-state properties of Py-BZTCN, the changes in its UV–vis absorption and PL spectra with increasing solvent polarity were examined. Py-BZTCN showed almost invariable absorption spectra in different solvents ( Supporting Information Figure S4). Obviously, PL spectra exhibited a solvatochromic red shift from λmax = 513 nm in hexane to λmax = 559 nm in DMSO with increasing solvent polarity together with the gradual disappearance of vibrational fine structures, indicating an evolution of excited-state character from locally excited (LE) to CT state (Figure 1a). NTOs were calculated based on optimized excited-state geometry, and hole and particle were distributed over the entire molecule. To distinguish between D and A, the dihedral angle (θ) between Py and BZTCN moieties was adjusted to be 90°. At this time, hole and particle were localized on Py and BZTCN, respectively, indicating that Py acted as D and BZTCN served as A ( Supporting Information Figure S5). The Lippert–Mataga model was used to estimate the excited-state dipole moment. The slopes of two-segment lines were fitted corresponding to the excited-state dipole moments of 6.57 and 12.34 D, respectively, which were much smaller than that (23 D) of the typical CT state of (N,N-dimethylamino)benzonitrile.52 This finding indicated a coexistence of LE and CT states, that is, hybridized local and CT (HLCT) state53–60 (Figure 1b and Supporting Information Table S1). By contrast, Py-BZT displayed a very small solvatochromic effect corresponding to a very weak CT or LE-dominated excited-state character ( Supporting Information Figure S6) owing to the absence of the strong electron-withdrawing cyano group. Notably, Py-BZTCN showed a very weak yellow-green monomer emission at λmax = 540 nm in tetrahydrofuran (THF) solution, and its PLQY was only 0.15%. However, Py-BZTCN began to aggregate and show enhanced emission when the water volume ratio reached 80% in THF/H2O mixture (Figure 1c and Supporting Information Figure S7), similar to the aggregation-induced emission enhancement (AIEE).61–66 Interestingly, Py-BZTCN aggregates in THF/H2O mixture (H2O fraction = 95%) showed red emission at λmax = 650 nm, which was even more red-shifted than the fluorescence in the strongly polar solvent DMSO and the orange-yellow emission of powders by column chromatography and sublimation, respectively (Figure 1d). This largely red-shifted emission could be related to a special aggregate formation instead of a CT emission of monomer as a result of the polarization effect in solid state. Conversely, Py-BZT did not show an obvious AIEE effect ( Supporting Information Figure S8). Figure 1 | (a) UV–vis absorption spectrum of Py-BZTCN in DMSO solvent and PL spectra of Py-BZTCN in different solvents. (b) Solvatochromic Lippert–Mataga models of Py-BZTCN. (c) PL spectra of Py-BZTCN in THF/H2O mixtures with different water fractions. (d) Fluorescence photographs of Py-BZTCN at 0% and 95% H2O fractions in THF/H2O mixtures (left) and Py-BZTCN powder purified by column chromatography (right top) and sublimation (right bottom), respectively. HEX, hexane; ETE, ethyl ether; ACN, acetonitrile. Download figure Download PowerPoint To clarify the aggregate structure, crystal growth was attempted by two methods, namely, sublimation and solvent diffusion. The needle-like O-type crystal was obtained by sublimation, and showed bright orange-yellow emission at λmax = 581 nm with a PLQY of 52.75% and a short lifetime (2.37 ns @ 72.72% and 3.90 ns @ 27.28%). Single-crystal XRD experiments revealed only the trans-isomer of Py-BZTCN in the O-type crystal, and two enantiomers can be readily distinguished (Figure 2a). O-type crystal showed one-dimensional long-range π–π stacking with an interplanar π–π distance of 3.563 Å and an overlap of about 20% between two Py groups, together with an interplanar π–π distance of 3.473 Å and a small overlap of 10% between adjacent benzothiazole groups, indicating relatively weak π–π interactions (Figure 2a and Supporting Information Figure S9). By contrast, a flocculent crystal of Py-BZTCN cultivated by solvent diffusion (THF/methanol) demonstrated red (R-type) emission at λmax = 676 nm with a PLQY of 12.63%. The lifetime measurement interestingly manifested short- (5.90 ns) and long-lived (4.12 μs) components corresponding to a prompt fluorescence and a delayed fluorescence, respectively ( Supporting Information Figure S10). Considering the close emission, this flocculent crystal should have a similar molecular packing to the aggregates in the THF/H2O mixture. Unfortunately, this R-type flocculent crystal was too tiny to be determined by structural analysis through single-crystal XRD. Figure 2 | (a) Conformation and stacking form of O-type crystal of Py-BZTCN. (b) Transformation progress of different samples through external stimuli. (c) PL spectra, (d) XRD pattern, and (e) DSC pattern of O-type crystal, ground sample, fumed sample, and R-type flocculent crystal of Py-BZTCN. Download figure Download PowerPoint Inspired by the relatively weak π–π interactions, the O-type crystal was ground to observe the possible change in emission color. Unexpectedly, the emission color changed from orange-yellow to red after grinding instead of a blue-shift (Figures 2b and 2c). The ground powder showed a very close emission spectrum to that of the R-type flocculent crystal, and its PLQY was measured to be 5.27%. Powder XRD experiments indeed revealed a real amorphous state of ground powder according to the disappearance of XRD patterns (Figure 2d). The 1H NMR spectrum of ground powder remained the same as that of the O-type crystal, indicating that the change in emission color was irrelevant to the isomerism between cis and trans, as well as the chemical reaction ( Supporting Information Figure S1). Interestingly, a heating or fuming treatment gave rise to a reversible luminescent return of ground powder from red to orange-yellow, along with the recovery of XRD patterns. DSC was further used to analyze the phase-transformation process among different samples. As shown in Figure 2e and Supporting Information Figure S11, the melting point (Tm) and the decomposition temperature (Td, according to 5 wt % loss by TGA) of Py-BZTCN were measured to be 218 and 386 °C, respectively. For ground powder, two exothermic peaks existed at 89 and 116 °C, corresponding to the crystallization of the amorphous state and phase transformation, respectively. The ground powder had the same Tm as that of the O-type crystal, indicating a metastable state of ground powder and a complete conversion from the amorphous into the O-type crystalline state by heating. The fumed sample exhibited the same DSC pattern as that of the O-type crystal, meaning that fuming can cause the complete transformation of the ground sample from the amorphous to the O-type crystalline state. However, the R-type floccule could be converted into the O-type crystal only by heating, accompanied with two thermal fluctuations in the DSC curve. The exothermic peak at 167 °C can be assigned to phase transformation, whereas the adjacent endothermic peak may be a pending question, which is expected to be answered after the structure solution of the R-type crystal. Overall, the DSC curve demonstrated that the R-type flocculent crystal was a metastable state relative to the O-type in the heating process. Besides the identical PL spectrum, R-type flocculent crystal and the ground amorphous powder were found to have a near-microsecond-long lifetime in fluorescence emission, and ground amorphous sample showed short- (7.97 ns) and long-lived (2.30 μs) components ( Supporting Information Figure S12). With increasing temperature, time-resolved PL spectra showed the gradually incremental long-lived component, indicating TADF emission through thermally activated RISC (Figures 3a and 3b). Meanwhile, both of them showed enhanced emission upon deoxygenation, further confirming the triplet exciton contribution through RISC ( Supporting Information Figure S13). Moreover, ΔEST was estimated to be 0.038 eV for the R-type flocculent crystal and 0.087 eV for ground powder according to the fluorescence and phosphorescence spectra at 77 K (Figure 3c). Such a small ΔEST was fully qualified for TADF generation by RISC from triplet to singlet states. All of the above results proved that the long-lived emission component was a TADF characteristic for the R-type flocculent crystal and amorphous ground powder. For comparison, the O-type crystal showed only normal fluorescence properties with near-monomer emission (similar to that of doped PMMA film), no delayed lifetime, and oxygen insensitivity, in accordance with the emission from the HLCT state ( Supporting Information Figure S14). Meanwhile, ΔEST was measured to be 0.686 eV for the Py-BZTCN monomer ( Supporting Information Figure S15) and 0.330 eV for O-type crystal (Figure 3c) respectively, which are usually too large to harvest TADF emission. Figure 3 | (a) Time-resolved spectra of R-type flocculent crystal with increasing temperature from 80 to 280 K in vacuum (temperature gradient: 50 K, inset: time-resolved spectrum of O-type crystal at 298 K). (b) Time-resolved spectra of ground sample with increasing temperature from 80 to 300 K in vacuum (temperature gradient: 20 K). (c) Prompt and delayed PL spectra of O-type crystal, R-type flocculent crystal, and ground sample at 77 K (orange and red line: fluorescence; blue line: phosphorescence after delay of 10 ms). (d) Conformation and stacking form of the R-type crystal of Py-BZTCN. Download figure Download PowerPoint Based on the above analysis, the R-type flocculent crystal and amorphous ground powder had almost identical photophysical properties, but why the grinding-induced phase transition from O-type crystal to amorphous state caused the TADF and red-shifted emission is unknown. Grinding treatment usually induces a disaggregation of the ordered aggregate (e.g., crystal) into the disordered state (e.g., amorphous powder), which results in a blue-shifted PL spectrum corresponding to an emission change from aggregate to monomer.67 In only two cases has grinding-induced red-shifted emission been attributed to the formation of excimer68–71 and the change in molecular conformation.3 First, Iwasaki and co-workers72 reported that the fluorescence of Py-octafluoronaphthalene cocrystals showed a red-shift from single-molecular Py emission to Py excimer emission by grinding. Nevertheless, this situation can be easily excluded in terms of the lifetime of amorphous powder because the lifetime of excimer fluorescence often lasts as long as tens or hundreds of nanoseconds (<300 ns) in an organic aromatic system.73–76 The second case is the study by Yasuda et al.3, who proposed another mechanism for grinding-induced red-shifted emission. For this mechanism, shear forces could control the torsional degree of molecular conformation in the twisted intramolecular CT-excited state, leading to different emission colors and TADF lifetimes.3 Additionally, some D–A derivatives of phenothiazine,77–82 phenoxazine,83,84 and 9,9-dimethyl-9,10-dihydroacridine85,86 are generally considered to have two distinct conformers, namely, quasi-axial and -equatorial conformers, which are responsible for normal fluorescence and TADF, respectively. However, both conformations of these compounds along with their related delayed-fluorescence properties have not been fully verified by crystal structure until now. Although an orthogonal conformation of Py-BZTCN showed HOMO–LUMO separation, small ΔEST, and red-shifted emission by theoretical simulation ( Supporting Information Figures S5 and S16), the actual red-shift of emission of R-type flocculent crystal and ground powder was far beyond its twisted intramolecular CT emission of monomer in a strongly polar solvent (e.g., DMSO). Thus, such a dual-responsive luminescence (color and lifetime) can be ascribed to other reasons instead of a change in molecular conformation. Considering the insufficient resolution of single-crystal XRD on a too slim crystal, synchrotron radiation XRD was performed to determine crystal packing in the R-type flocculent crystal (Figure 3d). Two trans-enantiomers were successfully identified clearly in the R-type crystal similar to those in the O-type crystal, but it was a cocrystalline state with the solvent inclusion of methanol. Most importantly, a closer π–π stacking mode with a larger cofacial overlap was found in the R-type crystal than in the O-type crystal, indicating a stronger π–π interaction in the R-type crystal than in the O-type crystal. The R-type crystal showed long-range face-to-face π–π stacking with an interplanar distance of 3.480 Å and an overlap degree of about 66% between Py groups, as well as an interplanar distance of 3.498 Å and an overlap of 40% between adjacent benzothiazole groups ( Supporting Information Figure S17). Compared with the O-type crystal, solvents offered more abundant noncovalent interactions to stabilize the metastable R-type crystal at room temperature ( Supporting Information Figure S18), also explaining why solvent fuming did not induce phase transition and emission change of the R-type crystal. Regarding the DSC pattern, the endothermic peak at 179 °C was confirmed to be due to the loss of solvent molecules. On account of the very similar molecular conformation between R- and O-type crystals, the significant differences in photophysical properties cannot be ascribed to the conformational change of Py-BZTCN. This intrinsic change in molecular packing with strengthened π–π interactions may be responsible for the red-shifted and TADF emission from O- to R-type crystal despite the similar H-aggregation between these two crystals ( Supporting Information Figure S19).87–89 Grinding force primarily disturbs the ordered π–π stacking of O-type crystal of Py-BZTCN into an amorphous state. However, some small-size aggregates randomly form with the compressed π–π distance and increased π–π overlap between nei" @default.
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• W3127681921 title "Thermally Activated Delayed Fluorescence of Aggregates Induced by Strong π–π Interactions and Reversible Dual-Responsive Luminescence Switching" @default.
• W3127681921 cites W1903035564 @default.
• W3127681921 cites W1963505485 @default.
• W3127681921 cites W1966957194 @default.
• W3127681921 cites W1970768075 @default.
• W3127681921 cites W1979487830 @default.
• W3127681921 cites W1981477318 @default.
• W3127681921 cites W1986591131 @default.
• W3127681921 cites W1987674325 @default.
• W3127681921 cites W1994724903 @default.
• W3127681921 cites W2001872081 @default.
• W3127681921 cites W2005259257 @default.
• W3127681921 cites W2018791417 @default.
• W3127681921 cites W2023954419 @default.
• W3127681921 cites W2029839561 @default.
• W3127681921 cites W2032185182 @default.
• W3127681921 cites W2034078366 @default.
• W3127681921 cites W2040191580 @default.
• W3127681921 cites W2044777503 @default.
• W3127681921 cites W2047346673 @default.
• W3127681921 cites W2058709487 @default.
• W3127681921 cites W2059185999 @default.
• W3127681921 cites W2059234830 @default.
• W3127681921 cites W2068405388 @default.
• W3127681921 cites W2069438188 @default.
• W3127681921 cites W2074053784 @default.
• W3127681921 cites W2089317723 @default.
• W3127681921 cites W2097864132 @default.
• W3127681921 cites W2134063343 @default.
• W3127681921 cites W2148561067 @default.
• W3127681921 cites W2148772155 @default.
• W3127681921 cites W2152047537 @default.
• W3127681921 cites W2168036745 @default.
• W3127681921 cites W2190305232 @default.
• W3127681921 cites W2233726204 @default.
• W3127681921 cites W2294868367 @default.
• W3127681921 cites W2313626922 @default.
• W3127681921 cites W2408583555 @default.
• W3127681921 cites W2487850372 @default.
• W3127681921 cites W2517162063 @default.
• W3127681921 cites W2605920122 @default.
• W3127681921 cites W2624598794 @default.
• W3127681921 cites W2770507099 @default.
• W3127681921 cites W2805370796 @default.
• W3127681921 cites W2888195268 @default.
• W3127681921 cites W2889122759 @default.
• W3127681921 cites W2924823614 @default.
• W3127681921 cites W2949216146 @default.
• W3127681921 cites W2957546222 @default.
• W3127681921 cites W2973348042 @default.
• W3127681921 cites W2977040496 @default.
• W3127681921 cites W3014676125 @default.
• W3127681921 cites W3022051471 @default.
• W3127681921 cites W3035572162 @default.
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