Inside Cover: Real‐time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda‐dimer by Ultrafast Time‐Domain Raman Spectroscopy (Angew. Chem. Int. Ed. 13/2022)

Hong, Yongseok; Kim, Woojae; Kim, Taeyeon; Kaufmann, Christina; Würthner, Frank; Kim, Dongho

doi:10.1002/anie.202202688

Cited by 7 publications

(23 citation statements)

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“…As shown in Figure S24, for rPBI-CP , the probe wavelength-dependent FFT map shows the prominent signals in the low-frequency region (0–1000 cm –1 ), whereas very weak signals are observed in the high-frequency region (1000–2000 cm –1 ). This is in good agreement with what we proposed before; the intense vibrational signals in the low-frequency region are characteristic of the excimer state due to vibronic coupling with the xOOP mode. , …”

Section: Resultssupporting

confidence: 93%

“…The photo-driven reaction, not vibrational cooling, is therefore highly attributed to the dephasing of xOOP mode VCs. Interestingly, the dephasing rates of these low-frequency modes are highly similar to the formation of the CT-resonance-enhanced excimer state, suggesting that these vibrational modes can be treated to the promotor modes in the reaction coordinates . Interestingly, oscillatory signals increase (within 1 ps) in the specific VC (∼316 cm –1 ).…”

Section: Resultsmentioning

confidence: 94%

“…Here, we note that a distortion effect of the PBI core is negligible since the twist of gPBI-CP (23.1°) lies between hitherto reported PBI dimers (0° for orange PBI dimer and 27° for rPBI-CP ) showing the excimer formation (Table S2). A photoexcited rPBI-CP exhibits the broad ESA band covering 600–950 nm, which is characteristic of the excimer, as shown in Figure a . Especially, except for a minor increase at 610–640 nm (Figure b), the overall shape of ESA retains its spectral characteristics during excimer formation ( k = 200 fs –1 ). ,,,− By contrast, the TA spectra of gPBI-CP show a prominent increase with a time constant of ∼180 fs in the ESA band (∼825 nm), corresponding to the radical anionic band, in both TOL and BCN (Figures c,d and S27).…”

Section: Resultsmentioning

confidence: 97%

“…A photoexcited rPBI-CP exhibits the broad ESA band covering 600–950 nm, which is characteristic of the excimer, as shown in Figure a . Especially, except for a minor increase at 610–640 nm (Figure b), the overall shape of ESA retains its spectral characteristics during excimer formation ( k = 200 fs –1 ). ,,,− By contrast, the TA spectra of gPBI-CP show a prominent increase with a time constant of ∼180 fs in the ESA band (∼825 nm), corresponding to the radical anionic band, in both TOL and BCN (Figures c,d and S27). However, the spectral shape in BCN is sharper compared with that in TOL.…”

Section: Resultsmentioning

confidence: 97%

“…In many stacked PBI arrays, intermolecular/intramolecular vibrations are often regarded as a key factor in triggering the ultrafast photoinduced phenomena such as excimer formation or singlet fission. Indeed, using time-resolved impulsive stimulated Raman spectroscopy, we recently revealed that the vibronic coupling with interchromophore out-of-plane (xOOP) mode plays a crucial role in excimer formation. , In this regard, we investigated the coherent vibrational wavepacket dynamics to figure out how the CT-resonance-enhanced excimer state can be formed even in a nonpolar solvent on an ultrafast time scale.…”

Section: Resultsmentioning

confidence: 99%

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Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

et al. 2022

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Perylene bisimides (PBIs) have received great attention in their applicability to optoelectronics. Especially, symmetry-breaking charge separation (SB-CS) in PBIs has been investigated to mimic the efficient light capturing and charge generation in natural light-harvesting systems. However, unlike ultrafast CS dynamics in donor−acceptor heterojunction materials, ultrafast SB-CS in a stacked homodimer has still been challenging due to excimer formation in the absence of rigidifying surroundings such as a special pair in the natural systems. Herein, we present the detailed mechanism of ultrafast photoinduced SB-CS occurring in a 1,7-bis(N-pyrrolidinyl) PBI dimer within a cyclophane. Through narrow-band and broad-band transient absorption spectroscopy, we demonstrate that ultrafast SB-CS in the dimer is enabled by the combination of (1) vibrationally coherent charge-transfer resonance-enhanced excimer formation and (2) breakdown of adiabaticity (formation of SB-CS diabats) in the excimer state via structural and solvent fluctuation. Quantum chemical calculations also underpin that the participation of strong electrondonating substituents in overall vibrational modes plays a crucial role in triggering the ultrafast SB-CS. Therefore, our work provides an alternative route to facilitate ultrafast SB-CS in PBIs and thereby establishes a novel strategy for the design of optoelectronic materials.

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

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Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

et al. 2022

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Switching Monomer‐to‐Excimer Fluorescence by Noncovalent Interaction Competition Strategy

Zhang

Wang

et al. 2023

Adv Funct Materials

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Noncovalent fluorescence switching materials with specific molecular packing motifs for desired performance are difficult to design accurately due to the complexity of intermolecular interactions. Herein, a noncovalent interaction competition strategy to design fluorescence-switching materials by fine-modulating hydrogen-bond and π-π interactions is proposed. Hydrogen bonds are generated by nitrogen/oxygen-containing units while π-π interactions are generated between polycyclic aromatic hydrocarbons. After these two interactions are balanced in strength, they attempt to induce the formation of respective molecule assemblies stably under controllable conditions. Through thermal stimulus produced by a laser, a reversible assembly transition with high-contrast monomer-to-excimer fluorescence switching is achieved, which demonstrates promising applications in rewritable optical recording and time-dependent anti-counterfeiting. This strategy provides a crucial step toward the controllable switching of supramolecular assembly for information handling.

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A Symmetry‐Broken Charge‐Separated State in the Marcus Inverted Region

Sebastian

Hariharan

2023

Angewandte Chemie

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We report a long‐lived charge‐separated state in a chromophoric pair (DC‐PDI2) that uniquely integrates the advantages of fundamental processes of photosynthetic reaction centers: i) Symmetry‐breaking charge‐separation (SB‐CS) and ii) Marcus‐inverted‐region dependence. The near‐orthogonal bichromophoric DC‐PDI2 manifests an ultrafast evolution of the SB‐CS state with a time constant of τSB-CS ${{\tau }_{{\rm S}{\rm B}-{\rm C}{\rm S}}}$ =0.35±0.02 ps and a slow charge recombination (CR) kinetics with τCR ${{\tau }_{{\rm C}{\rm R}}}$ =4.09±0.01 ns in ACN. The rate constant of CR of DC‐PDI2 is 11 686 times slower than SB‐CS in ACN, as the CR of the PDI radical ion‐pair occurs in the deep inverted region of the Marcus parabola ( -ΔGCR ${{-{\rm \Delta }G}_{{\rm C}{\rm R}}}$ >λ). In contrast, an analogous benzyloxy (BnO)‐substituted DC‐BPDI2 showcases a ≈10‐fold accelerated CR kinetics with τnormalCnormalR/τnormalSnormalB-normalCnormalS ${{\tau }_{{\rm C}{\rm R}}/{\tau }_{{\rm S}{\rm B}-{\rm C}{\rm S}}}$ lowering to ≈1536 in ACN, by virtue of a decreased CR driving force. The present investigation demonstrates a control of molecular engineering to tune the energetics and kinetics of the SB‐CS material, which is essential for next‐generation optoelectronic devices.

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Inside Cover: Real‐time Observation of Structural Dynamics Triggering Excimer Formation in a Perylene Bisimide Folda‐dimer by Ultrafast Time‐Domain Raman Spectroscopy (Angew. Chem. Int. Ed. 13/2022)

Cited by 7 publications

References 0 publications

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

Ultrafast Symmetry-Breaking Charge Separation in a Perylene Bisimide Dimer Enabled by Vibronic Coupling and Breakdown of Adiabaticity

Switching Monomer‐to‐Excimer Fluorescence by Noncovalent Interaction Competition Strategy

A Symmetry‐Broken Charge‐Separated State in the Marcus Inverted Region

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