Ratiometric pressure sensors based on cyano-substituted oligo(p-phenylene vinylene) derivatives in the hybridized local and charge-transfer excited state

Zhang, Yujian; Qile, Moge; Sun, Jingwei; Xu, Minhong; Wang, Kai; Cao, Feng; Li, Weijun; Song, Qingbao; Zou, Bo; Zhang, Cheng

doi:10.1039/c6tc03157a

Cited by 53 publications

(26 citation statements)

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“…Remarkably, the magnitude of the PL spectral shift for the TPEB‐α crystals upon increasing hydrostatic pressure (Δλ em,max = 212 nm) is unprecedented (Figure ). To elucidate the large redshift, we prepared the HLCT‐active luminophor mF‐TPA, which has PLQYs as high as 82.6% 8. However, the pressure‐induced redshift in mF‐TPA (Δλ em,max = 146 nm) was far smaller than that of TPEB‐α.…”

Section: Resultsmentioning

confidence: 99%

“…This combination is a “win‐win” tactic: the former contributes to high PLQYs, while the latter guarantees high sensitivity to external stimuli. Accordingly, HLCT‐type cyano‐substituted oligo(p‐phenylene vinylene) (CN‐OPV) demonstrated a clear bathochromic shift (Δλ max > 145 nm) in its PL color from the visible to the near‐IR region (λ max = 765 nm) upon exposure to high pressure . Clearly, D–π–A‐type luminophors with high brightness have great potential to show the clear color differences and strong penetrability characteristic.…”

Section: Introductionmentioning

confidence: 83%

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Highly Bright Fluorescence from Dispersed Dimers: Deep‐Red Polymorphs and Wide‐Range Piezochromism

Luo

Sheng

et al. 2020

Advanced Optical Materials

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applicability. [1b,2] At present, the practical requirements of flaw detection, haptic sensing, and deformation detection have promoted research into PCMs with strong penetrability and clear color differences (large spectral shifts). Compared with visible light, deep-red to infrared (IR) fluorescence has lower energy and longer PL wavelengths, giving it stronger penetrability. [3] Surprisingly, there are very few reports on PCMs with PL spectra that cover the deepred/near-IR regions and have clear color differences (>200 nm, Figure 1). [3b,4] In general, donor (D)-acceptor (A) luminophors generate an intramolecular charge transfer (CT) excited state in polar environments due to the twisting of the D-A bond. Interestingly, the CT state, which is highly sensitive to changes in the external environment, can induce tremendous shifts in the PL spectra. [4a,5] For instance, the He's group investigated the piezochromic behavior of two propeller-shaped boron difluoride complexes under high pressure.[5c] The intramolecular CT-type luminophor presented a larger color difference and higher sensitivity. However, such a CT state generally causes forbidden electronic transitions, leading to PL quenching. [5a,6] Thus, preparing near-IR luminophors with high PL quantum yields (PLQYs) is quite difficult. To solve this problem, Ma and another group reported D-A luminophores showing very bright near-IR fluorescence arising from the presence of a hybridized local and charge transfer (HLCT) state, which is a special excited state that possesses the characteristics of a locally excited (LE) state and CT character. [7] This combination is a "win-win" tactic: the former contributes to high PLQYs, while the latter guarantees high sensitivity to external stimuli. Accordingly, HLCT-type cyano-substituted oligo(p-phenylene vinylene) (CN-OPV) demonstrated a clear bathochromic shift (Δλ max > 145 nm) in its PL color from the visible to the near-IR region (λ max = 765 nm) upon exposure to high pressure. [8] Clearly, D-π-A-type luminophors with high brightness have great potential to show the clear color differences and strong penetrability characteristic. Nevertheless, during the compression, the PL intensity of PCMs is dramatically weakened as a consequence of conformational planarization and enhanced intermolecular π-π interactions, which is not conducive to further improving the piezochromic properties. [3b,9] Therefore, to realize high-performance piezochromic behavior, designing Near-infrared piezochromic materials (PCMs), which show a fluorescence response with a clear color difference and strong penetrability, have important potential applications, but few such organic luminophores have been reported. High-brightness donor (D)-acceptor (A) luminophores present great potential for preparing near-IR PCMs with clear color differences. However, the intermolecular π-π interactions are sharply enhanced at high pressures, which is not beneficial for the improvement of the piezochromic properties. Herein, two crystalline polymorphs (...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 83%

Highly Bright Fluorescence from Dispersed Dimers: Deep‐Red Polymorphs and Wide‐Range Piezochromism

Luo

Sheng

et al. 2020

Advanced Optical Materials

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“…The field of intermolecular CT crystals or salts mostly focused on high conductivity, superconductivity, or organic ferroelectrics properties,, and luminescence mechanochromism is still rare. To the best of our knowledge, the novelty of this work can be found in the following two points: a) High pressure study of luminescent co‐crystal with intermolecular CT interaction has not been reported, although the high pressure fluorescence study or intramolecular CT system has been reported ,,. b) An example of high‐pressure single‐crystal X‐ray diffraction analysis of piezochromic materials is still rare, although it has been performed for mono‐component crystal showing an excimer emission …”

Section: Figurementioning

confidence: 99%

“…As the applied pressure increased, the fluorescence emission of the 1 ⋅ guest clearly showed a gradual red shift, and the luminescence intensity gradually decreased (Figure a–c), which coincided with the previous results –,, For example, 1 ⋅ 4‐fluorotoluene showed a noticeable luminescence color change of over 100 nm from cyan (483 nm at 0.2 GPa) to red (593 nm at 8.7 GPa) under UV light excitation as shown in Figure a, which is more significant than upon mechanical grinding. Moreover, luminescence recovery from red to cyan was achieved under a decompression process.…”

Section: Figurementioning

confidence: 99%

Piezofluorochromism in Charge‐Transfer Inclusion Crystals: The Influence of High Pressure versus Mechanical Grinding

et al. 2018

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The distinct piezochromic luminescent responses of chargeÀtransfer inclusion crystals, which consist of small aromatic guest molecules with naphthalenediimide derivatives, are reported. Reversible multichromism is observed over the entire visible region in response to high pressure, whereas a weak response to mechanical grinding is evident. High-pressure single-crystal X-ray diffraction analysis and TD-DFT calculations clearly suggest that high compression induces a closer arrangement with a short interfacial distance between small aromatic guest molecules and naphthalenediimide derivatives, which is proposed as the origin of the drastic luminescent color change.The development of luminescent molecules that are sensitive to external stimuli has attracted considerable attention in recent years owing to their potential applications, such as in bioimaging, display, memory, and sensors. [1,2] Materials sensitive to external stimuli, such as pH, light, and temperature, have been relatively well investigated, whereas piezochromic luminescent materials, which change their luminescence upon mechanical grinding/shearing or high compression, remain poorly understood. Indeed, a number of mechanochromic systems, based on organic molecules [3] and metal complexes, [4] have been developed. In early stages of research, high-pressure effects on the electrostatic structure of organic crystals such as anthracene, chrysene, and pyrene were reported. [5] Based on the recent advance in understanding the mechanochromic systems, Zou, Tian and co-workers have reported anthracenederivatives, which exhibit mechanochromism after mechanical grinding and high pressure. [3a] In 2013, Saito, Yamaguchi and co-workers reported a propeller-shaped tetrathiazoylthiophene whose luminescence displayed distinct emission color changes in response to mechanical grinding and high pressure. [3c] Intramolecular charge-transfer (CT) fluorophores with an electron acceptor (A) and an electron donor (D) were used to demonstrate photoluminescence color changes in response to mechanical grinding and high pressure. In the molecular designs, intramolecular rotation of phenyl rings and packing modes, such as p-p stacked aggregates or amorphous states, are essential to tune the emission properties. However, the organic molecules that have been reported so far possess a major drawback. Most of the organic molecules that exhibit mechanochromism show the change of molecular packing modes and molecular torsion angles based on monomer emission, excimer emission, and intramolecular CT emission. Therefore, when grinding or smashing to make the crystal smaller, the crystal structure unexpectedly changes or collapses to form an amorphous powder. It is necessary to use pristine crystals when evaluating the piezochromic properties against high pressure. To the best of our knowledge, organic molecules that show a weak fluorescence response to mechanical grinding/smashing (anisotropic pressure) but significant response to high pressure (quasi-isotropic pressure) are rare.A...

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“…In addition, a clear decreasing trend of the h PL in the different solvents is observed, which is ascribed to the CT effect depending on solvent polarity. 19,20 To evaluate the solvatochromic effect, the Lippert-Mataga model is applied to estimate the dipole moment (m e ) of the excited state. The plot of Stokes shi against orientation polarizability (Df) is shown in Fig.…”

Section: Solvatochromic Effectmentioning

confidence: 99%

Stimuli-responsive fluorescence switching of cyanostilbene derivatives: ultrasensitive water, acidochromism and mechanochromism

Wang

Wei

2018

RSC Adv.

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A novel donor-p-acceptor structure stimuli-responsive fluorescent material of (Z)-2-(4 0 -(diphenylamino)-[1,1 0 -biphenyl]-4-yl)-3-(pyridin-2-yl)acrylonitrile (oN-TPA) was designed and synthesized, with the cyanogroup and pyridine as the acceptors (A) and triphenylamine as the donor (D). oN-TPA exhibits an obvious solvatochromic effect and the excited state is confirmed to be a hybridized local and charge-transfer (HLCT) state that simultaneously possesses the locally-excited (LE) state and charge transfer (CT) state characters. The LE state ensures relatively high fluorescence efficiency while the CT state provides multistimuli responsive fluorescence behaviors because it is easily tuned by the surrounding environment.Firstly, oN-TPA exhibits "on-off-on" fluorescence properties in the mixture of water/tetrahydrofuran (THF) with the increasing water content. For the "on-off" part, a good linear relationship between fluorescence intensity and water fraction is achieved, which is ascribed to the synergistic effect of protons in water and intramolecular charge-transfer (ICT) effect depending on solvent polarity. The "off-

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Ratiometric pressure sensors based on cyano-substituted oligo(p-phenylene vinylene) derivatives in the hybridized local and charge-transfer excited state

Abstract: D–A type dye exhibits high emission efficiency and ratiometric piezochromism behavior due to HLCT characteristics.

Cited by 53 publications

References 58 publications

Highly Bright Fluorescence from Dispersed Dimers: Deep‐Red Polymorphs and Wide‐Range Piezochromism

Highly Bright Fluorescence from Dispersed Dimers: Deep‐Red Polymorphs and Wide‐Range Piezochromism

Piezofluorochromism in Charge‐Transfer Inclusion Crystals: The Influence of High Pressure versus Mechanical Grinding

Stimuli-responsive fluorescence switching of cyanostilbene derivatives: ultrasensitive water, acidochromism and mechanochromism

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