Siloxy Group-Induced Highly Efficient Room Temperature Phosphorescence with Long Lifetime

Shimizu, Masaki; Shigitani, Ryosuke; Nakatani, Masaki; Kuwabara, Keiko; Miyake, Yusuke; Tajima, Kunihiko; Sakai, Hayato; Hasobe, Taku

doi:10.1021/acs.jpcc.6b03276

Cited by 109 publications

(60 citation statements)

References 51 publications

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“…The well‐known way to suppress the nonradiative decay is reducing the temperature, which can provide a rigid molecular environment to boost UOP, whereas their application fields are extremely limited due to the harsh conditions of low temperature. As a preferable choice, the UOP became more intriguing under ambient condition recently, and has been achieved by suppressing the nonradiative decay of triplet excitons via several strategies, such as host–guest doping, crystallization, the construction of metal–organic frameworks, polymerization, H‐aggregation, and other methods . In other words, the restriction of the molecular motions such as rotation, vibration, etc.…”

Section: Photophysical Properties Of 24fpb 2fpb 234fpb and 23fpb Cmentioning

confidence: 99%

Prolonging Ultralong Organic Phosphorescence Lifetime to 2.5 s through Confining Rotation in Molecular Rotor

Ling

Shi

et al. 2019

Advanced Optical Materials

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provide a rigid molecular environment to boost UOP, [16] whereas their applica tion fields are extremely limited due to the harsh conditions of low temperature. As a preferable choice, the UOP became more intriguing under ambient condi tion recently, and has been achieved by suppressing the nonradiative decay of triplet excitons via several strate gies, such as host-guest doping, [7,[17][18][19][20][21] crystallization, [22][23][24][25][26] the construction of metal-organic frameworks, [27,28] poly merization, [11,29,30] Haggregation, [31,32] and other methods. [33][34][35][36][37][38] In other words, the restriction of the molecular motions such as rotation, vibration, etc. is responsible for the UOP in solid state. However, the structure-property relationship of UOP is still ambigulous due to the complexity of molecular motions. Interestingly, molecular rotor provides a singnificant chance. Hence, by con structing a molecular rotor with UOP character, a fundamental understanding between molecular rotation and UOP property could be illustrated.Fluorine with the similar radius as hydrogen atom has high electronegativity, facilitating the formation of hydrogen bonding. [39] In crystal, the hydrogen bonding in fluorinated compounds can not only restrict the nonradiative decay with increased intermolecular interactions [22] but also adjust the radiative transition for fluorescence improvement. [40] In this work, by rationally tuning the fluoro position on phenylboronic acids, a series of fluorosubstituted phenylboronic acids deriva tives, namely 2,3difluorophenylboronic acid (23FPB), 2,3,4tri fluorophenylboronic acid (234FPB), 2fluorophenylboronic acid (2FPB), and 2,4difluorophenylboronic acid (24FPB) (Figure 1a), showed ultralong emission with lifetimes ranging from 0.36 to 2.50 s. Combining experimental and theoretical studies, it is proposed that the rotation confinement in the molecular rotors was mainly responsible for the prolonged UOP lifetime. With the introduction of fluorine atoms, the intramolecular OH···F hydrogen bonding made varied dihedral angles (θ) between benzene ring and boric acid group, implying that the triplet excitons can be influenced by the rotation in molecular rotors. Further theoretical calculations also confirmed that the rotation between benzene ring and boric acid group was cor responding to the low vibration mode for tuning nonradiative transitions. Therefore, the UOP lifetime can also be adjusted Developing ultralong organic phosphorescence (UOP) materials has become a growing concern. To date, it remains a formidable challenge to prolong the lifetime of ultralong phosphorescence under ambient conditions. A series of fluoro-substituted phenylboronic acid derivatives with UOP feature under ambient conditions is reported here. The UOP lifetime of 2,4-difluorophenylboronic acid (24FBP) crystal is up to 2.50 s, which is the longest emission lifetime among the reported single-component pure organic phosphors. Combining the experimental and theoretical study, upon stabilization of triple...

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Section: Photophysical Properties Of 24fpb 2fpb 234fpb and 23fpb Cmentioning

confidence: 99%

Prolonging Ultralong Organic Phosphorescence Lifetime to 2.5 s through Confining Rotation in Molecular Rotor

Ling

Shi

et al. 2019

Advanced Optical Materials

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“…So far,r esearchers have tried to promote the spin-orbit coupling (SOC) and subsequent intersystem crossing( ISC) through incorporation of carbonyl groups (C=O), halogens, and heteroatoms. [17,[20][21][22]31] At the same time, several other approaches, including radical-ion pairs, [32] s-n conjugation, [33] crystallization, [24,[34][35][36][37] embeddingi n ar igid matrix, [9,[38][39][40] Ha ggregation, [8,31,41] metal-organic frameworks or organic-inorganic perovskites, [42][43][44] have been proposed to stabilize the triplet excitons as am eans to achieve efficient p-RTP luminogens.…”

Section: Introductionmentioning

confidence: 99%

Polymorphic Pure Organic Luminogens with Through‐Space Conjugation and Persistent Room‐Temperature Phosphorescence

Zhang

Zhao

et al. 2019

Chemistry An Asian Journal

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Pure organic luminogens with persistent room‐temperature phosphorescence (p‐RTP) have attracted increasing attention owing to their vital significance and potential applications in security inks, bioimaging, and photodynamic therapy. Previously reported p‐RTP luminogens normally possessed through‐bond conjugation. In this work, we report a pure organic luminogen, AN‐MA, the Diels–Alder cycloaddition adduct of anthracene (AN) and maleic anhydride (MA), which possesses isolated phenyl groups and an anhydride moiety. AN‐MA exhibits aggregation‐enhanced emission (AEE) characteristics with efficiency of approximately 2 % and up to 8.5 % in solution and crystals, respectively. Two polymorphs of AN‐MA were readily obtained that were able to generate UV emission from individual phenyl rings together with bright blue emission owing to the effective through‐space conjugation. Moreover, p‐RTP with a lifetime of up to approximately 1.6 s was obtained in the crystals. These results not only reveal a new system with both fluorescence and RTP dual emission but also suggest an alternative through‐space conjugation strategy towards pure organic p‐RTP luminogens with tunable emissions.

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“…[12] In the host-guest molecular materials, the highly rigid short conjugated matrix could suppress k q (RT) caused by endothermic triplet-triplet energy transfer from guest to host molecules and effectively protect triplet excited species from oxygen, contributing substantially to the appearance of persistent RTP. [56] However, for most heavy atom-free conjugated molecular crystals with persistent RTP, [9,[14][15][16]25,26,[46][47][48][49][50][51] the quantum yield of persistent RTP (Φ p (RT)) of conjugated molecular crystals with an RTP lifetime approaching to 1 s is often a few percent or less. [56] However, for most heavy atom-free conjugated molecular crystals with persistent RTP, [9,[14][15][16]25,26,[46][47][48][49][50][51] the quantum yield of persistent RTP (Φ p (RT)) of conjugated molecular crystals with an RTP lifetime approaching to 1 s is often a few percent or less.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13][14][15][16][17] Because heavy atom-free molecules with T 1 with strong ππ* characteristics have very small k p , [18] RTP from such conjugated structures exhibits persistent emission characteristics. [32][33][34][35][36][37][38] Except for a few reports before 2000, [9,10] persistent RTP characteristics under ambient conditions have been observed recently from heavy atom-free isolated conjugated molecules doped in a highly rigid amorphous host [12,20,21,[39][40][41] and crystalline host, [42,43] carbon nanodots, [13,[22][23][24]44,45] heavy atom-free aromatic crystals, [14][15][16]25,26,[46][47][48][49][50][51][52] metal-organic frameworks, [17,53] and nonconventional luminogens. [19] Therefore, these materials are potentially useful for a variety of applic...…”

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confidence: 99%

Roles of Localized Electronic Structures Caused by π Degeneracy Due to Highly Symmetric Heavy Atom‐Free Conjugated Molecular Crystals Leading to Efficient Persistent Room‐Temperature Phosphorescence

Hirata

2019

Advanced Science

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Conjugated molecular crystals with persistent room‐temperature phosphorescence (RTP) are promising materials for sensing, security, and bioimaging applications. However, the electronic structures that lead to efficient persistent RTP are still unclear. Here, the electronic structures of tetraphenylmethane (C(C 6 H 5 ) 4 ), tetraphenylsilane (Si(C 6 H 5 ) 4 ), and tetraphenylgermane (Ge(C 6 H 5 ) 4 ) showing blue‐green persistent RTP under ambient conditions are investigated. The persistent RTP of the crystals originates from minimization of triplet exciton quenching at room temperature not suppression of molecular vibrations. Localization of the highest occupied molecular orbitals (HOMOs) of the steric and highly symmetric conjugated crystal structures decreases the overlap of intermolecular HOMOs, minimizing triplet exciton migration, which accelerates defect quenching of triplet excitons. The localization of the HOMOs over the highly symmetric conjugated structures also induces moderate charge‐transfer characteristics between high‐order singlet excited states (S m ) and the ground state (S 0 ). The combination of the moderate charge‐transfer characteristics of the S m –S 0 transition and local‐excited state characteristics between the lowest excited triplet state and S 0 accelerates the phosphorescence rate independent of the vibration‐based nonradiative decay rate from the triplet state at room temperature. Thus, the decrease of triplet quenching and increase of phosphorescence rate caused by the HOMO localization contribute to the efficient persistent RTP of Ge(C 6 H 5 ) 4 crystals.

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Siloxy Group-Induced Highly Efficient Room Temperature Phosphorescence with Long Lifetime

Cited by 109 publications

References 51 publications

Prolonging Ultralong Organic Phosphorescence Lifetime to 2.5 s through Confining Rotation in Molecular Rotor

Prolonging Ultralong Organic Phosphorescence Lifetime to 2.5 s through Confining Rotation in Molecular Rotor

Polymorphic Pure Organic Luminogens with Through‐Space Conjugation and Persistent Room‐Temperature Phosphorescence

Roles of Localized Electronic Structures Caused by π Degeneracy Due to Highly Symmetric Heavy Atom‐Free Conjugated Molecular Crystals Leading to Efficient Persistent Room‐Temperature Phosphorescence

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