Anti-Kasha’s Rule Fluorescence Emission in (2-Ferrocenyl)indene Generated by a Twisted Intramolecular Charge-Transfer (TICT) Process

Scuppa, Stefano; Orian, Laura; Donoli, Alessandro; Santi, Saverio; Meneghetti, Moreno

doi:10.1021/jp2021227

Cited by 50 publications

(36 citation statements)

References 31 publications

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“…Aromatic radical anions are known to exhibit broad absorbances in the 600–800 nm range as is aqueous solvated electron. 21 – 23 The observed excited state absorbance signal at ~550 nm also matches the absorbance profile expected for a general acridine exitonic structure. Simple first-order decay to the ground state occurs after ~100 ps, matching well with previously reported values for excited state lifetimes of organic radicals.…”

supporting

confidence: 71%

Discovery and characterization of an acridine radical photoreductant

Mackenzie

Wang

Onuska

et al. 2020

Nature

394

363

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Summary: Photoinduced electron transfer (PET) is a phenomenon wherein the absorption of light by a chemical species provides an energetic driving force for an electron transfer reaction. 1 – 4 This mechanism is relevant in many areas of chemistry, including the study of natural and artificial photosynthesis, photovoltaics, and photosensitive materials. In recent years, research in the area of photoredox catalysis has leveraged PET for the catalytic generation of both neutral and charged organic free radical species. These technologies have enabled a wide range of previously inaccessible chemical transformations and have seen widespread utilization in both academic and industrial settings. These reactions are often catalyzed by visible-light absorbing organic molecules or transition-metal complexes of ruthenium, iridium, chromium, or copper. 5 , 6 While a wide variety of closed shell organic molecules have been shown to behave as competent electron transfer catalysts in photoredox reactions, there are only limited reports of PET reactions involving neutral organic radicals as an excited state donor or acceptor. This is perhaps somewhat unsurprising in light of previously reported doublet excited state lifetimes for neutral organic radicals, which are typically several orders of magnitude shorter than singlet lifetimes for known transition metal photoredox catalysts. 7 – 11 Herein we document the discovery, characterization, and reactivity of a neutral acridine radical with a maximum excited state oxidation potential of −3.36 V vs. SCE: significantly more reducing than elemental lithium and marking it as one of the most potent chemical reductants reported. 12 Spectroscopic, computational, and chemical studies indicate that the formation of a twisted intramolecular charge transfer species enables the population of higher energy doublet excited states, leading to the observed potent photoreductant behavior. We demonstrate that this catalytically-generated PET catalyst facilitates several chemical reactions that typically require alkali metal reductants and bodes well for the adoption of this system in additional organic transformations requiring dissolving metal reductants.

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supporting

confidence: 71%

Discovery and characterization of an acridine radical photoreductant

Mackenzie

Wang

Onuska

et al. 2020

Nature

394

363

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“…Then we tried various functionals including M06, M062X, MPW1B95, PBE33, PBE38, and PBE0 that have different Hartree–Fock hybrid proportions to optimize the structure, and the f values are still nearly equal to zero for the electronic transition from S 1 to S 0 (Table S2, Supporting Information), disclosing that S 1 is indeed a dark state. Instead, the efficient emission of DMF‐BP‐PXZ actually should originate from the radiative relaxation of the higher energy electronic excited state, which doesn't obey Kasha's rule . Next, the second excited state (S 2 ) geometry was further optimized using the MPW1B95 and PBE0 functional.…”

Section: Resultsmentioning

confidence: 99%

Mechanical Insights into Aggregation‐Induced Delayed Fluorescence Materials with Anti‐Kasha Behavior

et al. 2018

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Organic materials with aggregation‐induced delayed fluorescence (AIDF) have exhibited impressive merits for improving electroluminescence efficiency and decreasing efficiency roll‐off of nondoped organic light‐emitting diodes (OLEDs). However, the lack of comprehensive insights into the underlying mechanism may impede further development and application of AIDF materials. Herein, AIDF materials consisting of benzoyl serving as an electron acceptor, and phenoxazine and fluorene derivatives as electron donors are reported. They display greatly enhanced fluorescence with increased delayed component upon aggregate formation. Experimental and theoretical investigations reveal that this AIDF phenomenon can be rationally ascribed to the suppression of internal conversion and the promotion of intersystem crossing in solid. Moreover, the theoretical calculations disclose that the efficient solid‐state delayed fluorescence originates from the higher energy electronic excited state (e.g., S2) rather than the lowest energy‐excited state (S1), demonstrating an anti‐Kasha behavior. The excellent AIDF property allows high exciton utilization and thus superb performance of OLEDs using these new materials as light‐emitting layers.

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“…At this point, PMPBAP luminescence does not comply with Kasha's rule. [34][35][36] The emission wavelength or emission spectrum appears red shift with the increase of excitation wavelength. This phenomenon originates from the clusters with different aggregated structural units of PMPBAP, which conforms to the general characteristics AIE.…”

Section: Aie Features Of Paasmentioning

confidence: 99%

Synthesis and Aggregation‐Induced Emission of Polyamide‐Amines as Fluorescent Switch Controlled by Hg²⁺‐Glutathione

et al. 2022

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In this study, a series of polyamide‐amines (PAAs) were prepared by Michael addition reaction of piperazine derivatives with N, N‐bisacrylamidepiperazine (BAP). An obvious aggregation‐induced emission (AIE) effect was observed for PAAs with fluorescence emission at 425–525 nm and affected by the structure, excitation wavelength, pH value, temperature, PAAs concentration and precipitant (acetone). The piperazine rings and amides groups on PAAs backbone contribute to their AIE by the clusterization‐triggered emission (CTE) mechanism, in accordance with the red‐shift of time‐dependent density functional theory (DFT). The DFT results proved the influence of packing way on aggregation luminescence, clarified the cluster mechanism of luminescences, and the ultraviolet absorption spectrum of PAAs. Additionally, based on the coordination, Hg2+ ions effectively quenched the fluorescence intensity of PAAs and showed enhanced quenching effect with the increase of concentration of Hg2+ ions. And also, a reducing agent, glutathione, can restore the fluorescence of PAAs solution mixed with Hg2+ ions, by which realizes the reversible switching process between fluorescence on and fluorescence off.

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Anti-Kasha’s Rule Fluorescence Emission in (2-Ferrocenyl)indene Generated by a Twisted Intramolecular Charge-Transfer (TICT) Process

Cited by 50 publications

References 31 publications

Discovery and characterization of an acridine radical photoreductant

Discovery and characterization of an acridine radical photoreductant

Mechanical Insights into Aggregation‐Induced Delayed Fluorescence Materials with Anti‐Kasha Behavior

Synthesis and Aggregation‐Induced Emission of Polyamide‐Amines as Fluorescent Switch Controlled by Hg²⁺‐Glutathione

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Anti-Kasha’s Rule Fluorescence Emission in (2-Ferrocenyl)indene Generated by a Twisted Intramolecular Charge-Transfer (TICT) Process

Cited by 50 publications

References 31 publications

Discovery and characterization of an acridine radical photoreductant

Discovery and characterization of an acridine radical photoreductant

Mechanical Insights into Aggregation‐Induced Delayed Fluorescence Materials with Anti‐Kasha Behavior

Synthesis and Aggregation‐Induced Emission of Polyamide‐Amines as Fluorescent Switch Controlled by Hg2+‐Glutathione

Contact Info

Product

Resources

About

Synthesis and Aggregation‐Induced Emission of Polyamide‐Amines as Fluorescent Switch Controlled by Hg²⁺‐Glutathione