Elucidating the Excited State of Mechanoluminescence in Organic Luminogens with Room‐Temperature Phosphorescence

Yang, Jie; Gao, Xuming; Xie, Zongliang; Gong, Yaqiong; Fang, Manman; Peng, Qian; Chi, Zhenguo; Li, Zhen

doi:10.1002/anie.201708119

Cited by 235 publications

(142 citation statements)

References 32 publications

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“…In particular,t he transformations of molecular conformation, such as trans-cis isomerization and excitedstate intramolecular proton transfer (ESIPT), have often been used to realize the dynamic PL process. [8] Then the questions arise whether the ML process is also sensitive to the molecular conformation or whether is it just the same as the PL behavior. [7] Inspired by similar energy level features between ML and PL processes,w et hen made an initial attempt to reveal the excited state of mechanoluminescence in the organic luminogen CzS-C 2 H 5 with the mature PL theory acting as template in 2017, and found that the change of packing mode under the mechanical stimulus played an important role in the ML process.…”

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confidence: 99%

Molecular Conformation‐Dependent Mechanoluminescence: Same Mechanical Stimulus but Different Emissive Color over Time

et al. 2018

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Ap henothiazine derivative of FCO-CzS with changeable mechanoluminescence is reported, which,u pon continuous mechanical stimulus,s hows mechanoluminescent emission from blue to white and yellow.Careful analysis of the experimental results,c oupled with the well-understood photoluminescence theory,s how that the molecular conformation transition of the phenothiazine group from quasi-axial to quasi-equatorial is responsible for this dynamic mechanoluminescence effect.

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Molecular Conformation‐Dependent Mechanoluminescence: Same Mechanical Stimulus but Different Emissive Color over Time

et al. 2018

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“…[35] Phenothiazines are well-known classes of compounds for application in thermally activated delayed fluorescence (TADF), because of the ease of intersystem crossing from their singlet to triplet states and vice versa. [35] Phenothiazines are well-known classes of compounds for application in thermally activated delayed fluorescence (TADF), because of the ease of intersystem crossing from their singlet to triplet states and vice versa.…”

Section: Phosphorescent Triboluminescent Materialsmentioning

confidence: 99%

Renaissance of Organic Triboluminescent Materials

Mukherjee

Thilagar

2019

Angew Chem Int Ed

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Solid‐state luminescence of organic dyes is an elusive frontier, and understanding and designing solid‐state stimuli‐responsive materials is not trivial. “Mechanoluminescence” (ML) or “triboluminescence” (TL), which is associated with fracture or force‐initiated luminescence from a material, is currently attracting new interest. Fracturing the surfaces of organic crystals ordered in noncentrosymmetric space groups can electronically excite the surface and neighboring molecules through piezo‐ or pyroelectric effects, and this can result in luminescence when the molecules relax back to their ground states. The combined duration of these two consecutive phenomena leads to force‐generated luminescence or TL. Although TL has been known for a very long time, examples of TL‐active materials are scarce, but are increasing as synthetic and characterization procedures develop. The question is now whether the relatively rare phenomenon of TL needs to be reevaluated to obtain a broader understanding of the subject.

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“…[5,13] Forisolated BrFluÀCBr, although there are two main channels with two minor channels,t he smallest energy gap of 0.1052 eV can be only found in aminor channel between S 1 and T 5 (Figure 4). Thec onfigurations of the excited state and possible ISC of monomers and dimers were calculated by the timedependent density-functional theory (TD-DFT).…”

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“…Actually,t he light is green-white and the difference is apparent under soft light (Figure 2e). [13] Furthermore,after continuous grinding, the crystalline sample was converted into powder with weak blue emission under the mechanical stimulus (Figure 2d, inset). [13] Furthermore,after continuous grinding, the crystalline sample was converted into powder with weak blue emission under the mechanical stimulus (Figure 2d, inset).…”

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Bromine‐Substituted Fluorene: Molecular Structure, Br–Br Interactions, Room‐Temperature Phosphorescence, and Tricolor Triboluminescence

et al. 2018

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Organic tribophosphorescence materials are rarely reported and the introduction of Br atoms mayb eapractical way to design such materials.H ere four bromine-substituted fluorene-based derivatives are presented and BrFlu À CBr, having fluorescence-phosphorescence dual-emission induced not only by UV light but also by mechanical stimulus,manifests the highest phosphorescence efficiency of 4.56 %upon photoirradiation. During the grinding process,t hree different triboluminescent spectra were identified. Upon introduction of am echanical stimulus,t he triboluminescence emission is cyan, whereas after an extended period it changed to blue.After removing the mechanical stimulus,g reen-white phosphorescent emission was observed. Careful research on single-crystal structures and theoretical calculations demonstrate that strong Br···Br interactions are vital to facilitate spin-orbit coupling and promote intersystem crossing, thus generating the unique properties.Mechanoluminescence (ML), including piezoluminescence,t riboluminescence,a nd sonoluminescence,i sl uminescence induced by application of am echanical stimulus to asolid. [1] With potential applications in areas such as lighting sources,p ressure sensors,a nd display devices,m echanoluminescence is still attracting widespread interest despite its longstanding history,w hich can be traced back to the first report by Francis Bacon in 1605. [1,2] However,the number of purely organic ML luminogens remains limited and many organic ML compounds only have UV emission bands,t hus making the exploration of the ML process and achieving practical applications difficult. [1b, 3] Therefore there is an urgent need to develop more ML materials so as to learn about the relationship between the mechanoluminescence phenomena and molecular structure.A san ecessary process in either photoluminescence or electroluminescence for thermally activated delayed fluorescence (TADF) materials and phosphores-cence materials,the intersystem crossing (ISC) has been well investigated. [4] However,the ISC transition upon mechanical stimulus is hardly mentioned. Recently,o ur group presented the first report on an unusual mechanophosphorescence luminogen with aggregation-induced emmision (AIE) properties and the successful marriage of ML and ISC. [5] As ac onsequence,i ti sp ossible to rationally design ML luminogens to increase the ISC efficiency.As am atter of fact, many effective approaches,f or instance,crystallization, enhancing p-p interactions,adopting compact face to face packing, expanding conjugation, and self-assembly in supramolecular frameworks,h ave been introduced to organics with phosphorescence at room temperature to study the problem of the highly forbidden tripletsinglet transitions. [6] Besides,the heavy-atom effect (HAE) is also known to be an impactful method for achieving astrong spin-orbit coupling (SOC) between excited singlet and triplet states and increasing the ISC rate constant. [7] In contrast, intermolecular halogen-bonding interactions,e specially CÀ Br···BrÀCi nter...

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Elucidating the Excited State of Mechanoluminescence in Organic Luminogens with Room‐Temperature Phosphorescence

Cited by 235 publications

References 32 publications

Molecular Conformation‐Dependent Mechanoluminescence: Same Mechanical Stimulus but Different Emissive Color over Time

Molecular Conformation‐Dependent Mechanoluminescence: Same Mechanical Stimulus but Different Emissive Color over Time

Renaissance of Organic Triboluminescent Materials

Bromine‐Substituted Fluorene: Molecular Structure, Br–Br Interactions, Room‐Temperature Phosphorescence, and Tricolor Triboluminescence

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