The Impact of C<sub>2</sub> Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[<i>a,j</i>]phenazine‐Cored Donor–Acceptor–Donor Triads

Crocomo, Paola Zimmermann; Kaihara, Takahito; Kawaguchi, Soki; Stachelek, Patrycja; Minakata, Satoshi; Silva, Piotr de; Data, Przemysław; Takeda, Yoshifumi

doi:10.1002/chem.202101654

Cited by 6 publications

(4 citation statements)

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“…The lower efficiency of the device based on compound 4d is associated with nonemissive recombination from the triplet state, and the DF/PF value is rather low which suggests that at least in the photoexcitated process, the energy from the triplet excited state is lost. Similar behaviour was observed in our previous study, 19 however, in that case we didn't observe a negative DE ST gap. In our current study, compound 4d exhibits better performance suggesting the continued study of such derivaties could bring promissing results in the future.…”

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confidence: 92%

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

et al. 2023

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supporting

confidence: 92%

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

et al. 2023

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“…On the other hand, D−A derivatives based on the IDB donor are well-known for their quasi-axial conformation, which pushes emission to the RTP mechanism. 45,46 Upon closer inspection of the behavior of isomers 54.1 and 54.4 in the CBP host, a small inversion was again observed, which straightforwardly supports the concept of the impact of quasi-axial conformation and TICT mechanisms. If the presence of the quasi-equatorial conformation were the case, the typical TADF mechanism would be observed.…”

Section: Steady-state Photophysicssupporting

confidence: 65%

Regioisomerism vs Conformation: Impact of Molecular Design on the Emission Pathway in Organic Light-Emitting Device Emitters

Govindharaj,

Wierzba,

Kęska

et al. 2024

ACS Appl. Mater. Interfaces

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Despite the design and proposal of several new structural motifs as thermally activated delayed fluorescent (TADF) emitters for organic light-emitting device (OLED) applications, the nature of their interaction with the host matrix in the emissive layer of the device and their influence on observed photophysical outputs remain unclear. To address this issue, we present, for the first time, the use of up to four regioisomers bearing a donor−acceptor−donor electronic structure based on the desymmetrized naphthalene benzimidazole scaffold, equipped with various electron-donating units and possessing distinguished conformational lability. Quantum chemical calculations allow us to identify the most favorable conformations adopted by the electron-rich groups across the entire pool of regioisomers. These conformations were then compared with conformational changes caused by the interaction of the emitter with the Zeonex and 4,4′bis(N-carbazolyl)-1,1′-biphenyl (CBP) matrices, and the correlation with observed photophysics was monitored by UV−vis absorption and steady-state photoluminescence spectra, combined with time-resolved spectroscopic techniques. Importantly, a CBP matrix was found to have a significant impact on the conformational change of regioisomers, leading to unique TADF emission mechanisms that encompass dual emission and inversion of the singlet−triplet excited-state energies and result in the enhancement of TADF efficiency. As a proof of concept, regioisomers with optimal donor positions were utilized to fabricate an OLED, revealing, with the best-performing dye, an external quantum emission of 11.6%, accompanied by remarkable luminance (28,000 cd/m 2 ). These observations lay the groundwork for a better understanding of the role of the host matrix. In the long term, this new knowledge can lead to predicting the influence of the host matrix and adopting the structure of the emitter in a way that allows the development of highly efficient and efficient OLEDs.

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“…An important feature of the D–A–D scaffold is that the emission color in solution can be tuned within the visible light region by modulating the electron-donating power of the bridging unit (Q) in the donor. Figure illustrates the correlation between the photoluminescence (PL) wavelength (λ em ) in toluene and the incorporated bridging unit. ,,,− When compared to a D–A–D compound with non-bridged donors (diphenylamine), incorporating divalent chalcogen atoms (O, S, Se) into the donor unit results in a significant red shift in PL of over 100 nm. These divalent chalcogen atoms possess lone pairs of electrons that can be donated into the π-electronic system, increasing the electron density of the donor units and facilitating charge separation (D + –A – ) in the excited state, which is further stabilized by the twisted D–A–D scaffold (i.e., twisted intramolecular charge transfer).…”

Section: Introductionmentioning

confidence: 99%

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Takeda

2024

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Modulating the photophysical properties of organic emitters through molecular design is a fundamental endeavor in materials science. A critical aspect of this process is the control of the excited-state energy, which is essential for the development of triplet exciton-harvesting organic emitters, such as those with thermally activated delayed fluorescence and roomtemperature phosphorescence. These emitters are pivotal for developing highly efficient organic light-emitting diodes and bioimaging probes. A particularly promising class of these emitters consists of twisted donor− acceptor organic π-conjugated scaffolds. These structures facilitate a spatial separation of the frontier molecular orbitals, which is crucial for achieving a narrow singlet−triplet energy gap. This narrow gap is necessary to overcome the endothermic reverse intersystem crossing process, enhancing the efficiency of thermally activated delayed fluorescence. To precisely modulate the photophysical properties of these emitting materials, it is essential to understand the electronic structures of new donor−acceptor scaffolds, especially those influenced by heteroatoms, as well as their conformations and topologies. This understanding not only improves the efficiency of these emitters but also expands their potential applications in advance technologies.In 2014, the Takeda group made a significant breakthrough by discovering a novel method for synthesizing U-shaped diazaacenes (dibenzo[a,j]phenazine) through an oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′-diamines. This class of compounds is typically challenging to synthesize using conventional organic reactions. The resulting unique geometric and electronic structure of U-shaped diazaacenes opened new possibilities for photophysical applications. Leveraging the U-shaped structure, photoluminescent properties, and high electron affinity, we developed twisted donor−acceptor−donor compounds. These compounds exhibit efficient thermally activated delayed fluorescence, stimuli-responsive luminochromism, heavy atom-free room-temperature phosphorescence, and anion-responsive red shifts. These innovative emitters have demonstrated significant potential in various practical applications, including organic light-emitting diode devices and advanced sensing systems. In this Account, I summarize our achievements in modulating the photofunctions of dibenzo[a,j]phenazine-cored twisted donor− acceptor−donor compounds by controlling excited-state singlet−triplet energy gaps through conformational regulation. Our comprehensive studies revealed the significant impact of heteroatoms, molecular conformations, and topologies on the photophysics of these compounds. These findings highlight the importance of molecular engineering in tailoring the photophysical properties of organic donor−acceptor π-conjugated materials for specific applications. Our research has demonstrated that incorporating heteroatoms into the molecular framework effectively tunes the...

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The Impact of C₂ Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine‐Cored Donor–Acceptor–Donor Triads

Cited by 6 publications

References 21 publications

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

Regioisomerism vs Conformation: Impact of Molecular Design on the Emission Pathway in Organic Light-Emitting Device Emitters

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

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The Impact of C2 Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine‐Cored Donor–Acceptor–Donor Triads

Cited by 6 publications

References 21 publications

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

V-shaped donor–acceptor organic emitters. A new approach towards efficient TADF OLED devices

Regioisomerism vs Conformation: Impact of Molecular Design on the Emission Pathway in Organic Light-Emitting Device Emitters

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

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The Impact of C₂ Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine‐Cored Donor–Acceptor–Donor Triads