Circularly polarized luminescence of achiral open-shell π-radicals

Jin, Qiong‐Hua; Chen, Sanxu; Sang, Yutao; Guo, Hongping; Dong, Shengzhi; Han, Jianlei; Chen, Wenjie; Yang, Xuefeng; Li, Feng; Duan, Pengfei

doi:10.1039/c9cc03281a

Cited by 53 publications

(39 citation statements)

References 43 publications

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“…In this sense,t he previously made AC assignment was corroborated experimentally too.T his good agreement can also be taken as adirect prove of the intrinsic CPL response of both atropisomers of 1 and 2.Onthe contrary,when analyzing the CPL activity of some achiral racemic mixtures included in chiral matrixes, [59] some inconsistencies can be found. [60] Regarding the different intensities detected in this work for the CPL spectra, they may arise from the large error in measurement due to the small values of the CPL [18] and, in the case of 1,t ogether with the different enantiomeric purity between the two (CSP)HPLC fractions.CPL activity from the racemic mixtures of both compound was also evaluated at the same working conditions that in the case of the enantioenriched solutions (10 À4 m in CCl 4 ,atÀ20 8 8C), with aclear DI % 0 in both cases (see Figure S16). In this sense,a ny significant contribution of linear polarization or optical artifacts was successfully ruled out.…”

Section: Resultsmentioning

confidence: 84%

Organic Free Radicals as Circularly Polarized Luminescence Emitters

et al. 2019

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Chiroptical properties of two chiral atropisomers of propeller‐like trityl‐based radical derivatives have been analyzed. A new absolute configuration (AC) assignment has been made, according to the combination of experimental and theoretical data. In this sense, their ACs have been determined through the comparison of the Cotton effects recorded by electronic circular dichroism (ECD) with the theoretical ECD of the open shell structures obtained by TD‐DFT calculations. Finally, their circularly polarized luminescence (CPL) responses have been addressed. Remarkably, this is the first description of organic free radicals as intrinsic CPL emitters. Opposite signed CPL has been detected for each pair of conformers, with acceptable luminescent dissymmetry factors (|glum|≈0.5–0.8×10−3) considering their pure organic nature. In fact, highly efficient chiral emissions have been demonstrated, according to the comparison of |glum| with their respective absorption anisotropy factors (|gabs|). This pioneering study lays the foundations for the optimization of new magnetically active organic chiral emitters.

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Section: Resultsmentioning

confidence: 84%

Organic Free Radicals as Circularly Polarized Luminescence Emitters

et al. 2019

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“…[ 21 ] Although the initial radical‐based OLEDs displayed only modest external quantum efficiencies (EQEs) around 2.4 %, follow‐up work led to new luminescent radicals that resulted in devices with higher efficiencies. [ 45–49 ] Recently, Li and co‐workers reported the fabrication of radical‐based OLEDs exploiting adducts between TTM and carbazole derivatives, with EQEs as large as ≈27%; such efficiencies point to ≈100% internal electroluminescence quantum yield. [ 24 ]…”

Section: Introductionmentioning

confidence: 99%

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Abroshan

Coropceanu

Brédas

2020

Adv Funct Materials

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Radical‐carrying organic molecules have received significant attention to bypass the issue related to harvesting triplet excitons in current light‐emitting materials. While the computational efforts conducted so far have treated these radical emitters as isolated entities, in actual devices, they are embedded in a host matrix and subject to emitter–host interactions. Here, by combining molecular dynamics simulations and density functional theory calculations, the impact of the host matrix on the optoelectronic performance of radical emitters is evaluated, taking as a representative example the (4‐ncarbazolyl‐2,6‐dichlorophenyl)bis(2,4,6‐trichlorophenyl)‐methyl (TTM‐3NCz) radical emitter dispersed in a 4,4‐bis(carbazol‐9‐yl)biphenyl (CBP) host. A morphological analysis shows that steric effects around the radical centers, carried by the TTM electron‐poor moieties of the emitters, disfavor π–π interactions with the host molecules, which leads to random intermolecular orientations around the TTM moieties. The 3NCz electron‐rich moieties of the emitters, however, have much lesser spatial hindrance for intermolecular π–π stacking, which modulates the structural and electronic properties of the emitters in the host matrix. The influence of dynamic and static disorders on the radiative and nonradiative recombination processes is also investigated and it is found that the rates of nonradiative recombination are small, which opens the way to 100% internal quantum efficiency for the doublet‐based emission process.

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“…On the contrary, when analyzing the CPL activity of some achiral racemic mixtures included in chiral matrixes, some inconsistencies can be found. [59] Regarding the different intensities detected in this work for the CPL spectra, they may arise from the large error in measurement due to the small values of the CPL. [18] CPL activity from the racemic mixtures of both compound was also evaluated at the same working conditions that in the case of the enantioenriched solutions (10 -4 M in CCl4, at -20 ºC), with a clear ΔI ≈ 0 in both cases (see Fig.…”

Section: Resultsmentioning

confidence: 83%

Organic Free Radicals as Circularly Polarized Luminescence Emitters

et al. 2019

View full text Add to dashboard Cite

Chiroptical properties of two chiral atropisomers of propeller-like trityl-based radical derivatives have been analyzed. A new absolute configuration (AC) assignment has been made, according to the combination of experimental and theoretical data. In this sense, their ACs have been determined through the comparison of the Cotton effects recorded by electronic circular dichroism (ECD) with the theoretical ECD of the open shell structures obtained by TD-DFT calculations. Finally, their circularly polarized luminescence (CPL) responses have been addressed. Remarkably, this is the first description of organic free radicals as intrinsic CPL emitters. Opposite signed CPL has been detected for each pair of conformers, with acceptable luminescent dissymmetry factors (|glum| ≈ 0.5-0.8 x 10-3) considering their pure organic nature. In fact, highly efficient chiral emissions have been demonstrated, according to the comparison of |glum| with their respective absorption anisotropy factors (|gabs|). This pioneering study lays the foundations for the optimizations of new magnetically active organic chiral emitters.

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Circularly polarized luminescence of achiral open-shell π-radicals

Abstract: Doublet emission-based circularly polarized luminescence was successfully realized in luminescent π-radicals by applying three kinds of approaches, namely, induction by a longitudinal magnetic field, supramolecular chiral co-assembly, and doping into chiral liquid crystals.

Cited by 53 publications

References 43 publications

Organic Free Radicals as Circularly Polarized Luminescence Emitters

Organic Free Radicals as Circularly Polarized Luminescence Emitters

Radiative and Nonradiative Recombinations in Organic Radical Emitters: The Effect of Guest–Host Interactions

Organic Free Radicals as Circularly Polarized Luminescence Emitters

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