Double J-Coupling Strategy for Near Infrared Emitters

Shen, Chia-An; Stolte, Matthias; Kim, Jin Hong; Rausch, Anja; Würthner, Frank

doi:10.1021/jacs.1c05934

Cited by 33 publications

(25 citation statements)

References 37 publications

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“…In this regard, we would like to stress on the importance of the energy gap law that manifests an increased vibrational coupling between electronic states if they are energetically close. For this reason, it is indeed challenging to accomplish a decent NIR emission at wavelengths beyond 800 nm. − The fluorescence of planar QBIref has been previously investigated in chloroform solution, showing a emission maximum (λ em ) at 797 nm with an estimated quantum yield (Φ Fl ) by the Strickler–Berg analysis of about 5% . We took the effort to experimentally investigate all three QBIs in DCM with a state-of-the-art liquid-nitrogen-cooled NIR photomultiplier (with a good signal-to-noise ratio even in the NIR wavelength range) as well as a calibrated integration sphere setup.…”

Section: Resultsmentioning

confidence: 99%

Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides

et al. 2022

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Graphene nanoribbons (GNRs) have the potential for next-generation functional devices. So far, GNRs with defined stereochemistry are rarely reported in literature and their optical response is usually bound to the ultraviolet or visible spectral region, while covering the near-infrared (NIR) regime is still challenging. Herein, we report two novel quaterrylene bisimides with either one-or twofold-twisted π-backbones enabled by the steric congestion of a fourfold bay arylation leading to an end-toend twist of up to 76°. The strong interlocking effect of the πstacked aryl substituents introduces a rigidification of the chromophore unambiguously proven by single-crystal X-ray analysis. This leads to unexpectedly strong NIR emissions at 862 and 903 nm with quantum yields of 1.5 and 0.9%, respectively, further ensuring high solubility as well as resolvable and highly stable atropo-enantiomers. Circular dichroism spectroscopy of these enantiopure chiral compounds reveals a strong Cotton effect Δε of up to 67 M −1 cm −1 centered far in the NIR region at 849 nm.

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Section: Resultsmentioning

confidence: 99%

Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides

et al. 2022

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“…Quadrupolar dye molecules composed of electron donor (D) and acceptor (A) groups linked by π-conjugated bridges are currently of substantial interest, mainly because of their large transition dipole moments, resulting from the extensively delocalized π electrons over the molecular backbone and their interesting nonlinear optical properties. , Squaraines are typical D−π–A−π–D type molecules, connecting two nitrogen-containing donors via a squaric acid acceptor. They exhibit a narrow absorption band at rather long wavelengths, with a high absorption coefficient on the order of ≥300,000 M –1 cm –1 , and comparatively high fluorescence quantum yields, which makes them good near IR absorbers and emitters . Squaraines are also highly promising as light absorbers and donor materials for efficient organic photovoltaic devices, , leading to power conversion efficiencies of 8% when combined with a fullerene acceptor and can improve the efficiency of polymer solar cells as an additive .…”

Section: Introductionmentioning

confidence: 99%

Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes

et al. 2022

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Squaraines are prototypical quadrupolar charge-transfer chromophores that have recently attracted much attention as building blocks for solution-processed photovoltaics, fluorescent probes with large two-photon absorption cross sections, and aggregates with large circular dichroism. Their optical properties are often rationalized in terms of phenomenological essential state models, considering the coupling of two zwitterionic excited states to a neutral ground state. As a result, optical transitions to the lowest S1 excited state are one-photon allowed, whereas the next higher S2 state can only be accessed by two-photon transitions. A further implication of these models is a substantial reduction of vibronic coupling to the ubiquitous high-frequency vinyl-stretching modes of organic materials. Here, we combine time-resolved vibrational spectroscopy, two-dimensional electronic spectroscopy, and quantum-chemical simulations to test and rationalize these predictions for nonaggregated molecules. We find small Huang–Rhys factors below 0.01 for the high-frequency, 1500 cm–1 modes in particular, as well as a noticeable reduction for those of lower frequency modes in general for the electronic S0 → S1 transition. The two-photon allowed state S2 is well separated energetically from S1 and has weak vibronic signatures as well. Thus, the resulting pronounced concentration of the oscillator strength in a narrow region relevant to the lowest electronic transition makes squaraines and their aggregates exceptionally interesting for strong and ultrastrong coupling of excitons to localized light modes in external resonators with chiral properties that can largely be controlled by the molecular architecture.

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“…After the serendipitous discovery of J-aggregates in the 1930s, − the interest in their photophysical properties has been emerging while finding practical applications, for instance in bioimaging, , dye chemistry, and other areas of materials chemistry. − The most well-known class of molecules forming J-aggregates is probably cyanine dyes, − but examples covering many other dye classes exist, including BODIPY dyes, − squaraine dyes, − and porphyrins, − among others. , Rylenes is a class of dyes based on fused naphthalenes, and J-aggregate-forming examples include mainly perylene bisimides. − …”

Section: Introductionmentioning

confidence: 99%

Exciton Delocalization Counteracts the Energy Gap: A New Pathway toward NIR-Emissive Dyes

Cravcenco

Edhborg

et al. 2021

J. Am. Chem. Soc.

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Exciton coupling between the transition dipole moments of ordered dyes in supramolecular assemblies, so-called J/H-aggregates, leads to shifted electronic transitions. This can lower the excited state energy, allowing for emission well into the near-infrared regime. However, as we show here, it is not only the excited state energy modifications that J-aggregates can provide. A bay-alkylated quaterrylene was synthesized, which was found to form J-aggregates in 1,1,2,2-tetrachloroethane. A combination of superradiance and a decreased nonradiative relaxation rate made the J-aggregate four times more emissive than the monomeric counterpart. A reduced nonradiative relaxation rate is a nonintuitive consequence following the 180 nm (3300 cm −1 ) red-shift of the J-aggregate in comparison to the monomeric absorption. However, the energy gap law, which is commonly invoked to rationalize increased nonradiative relaxation rates with increasing emission wavelength, also contains a reorganization energy term. The reorganization energy is highly suppressed in J-aggregates due to exciton delocalization, and the framework of the energy gap law could therefore reproduce our experimental observations. J-Aggregates can thus circumvent the common belief that lowering the excited state energies results in large nonradiative relaxation rates and are thus a pathway toward highly emissive organic dyes in the NIR regime.

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Double J-Coupling Strategy for Near Infrared Emitters

Cited by 33 publications

References 37 publications

Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides

Helically Twisted Nanoribbons Based on Emissive Near-Infrared Responsive Quaterrylene Bisimides

Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes

Exciton Delocalization Counteracts the Energy Gap: A New Pathway toward NIR-Emissive Dyes

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