Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes
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.
NI Journal Papers ; NI论文
Deutsche Forschungsgemeinschaft["SPP1839","SFB1372","INST 184/163-1","INST 184/164-1","Li 580/16-1","DE 3578/3-1"] ; Deutsche Forschungsgemeinschaft within Graduate School "Molecular Basis of Sensory Biology"[RTG 1885] ; Deutsche Forschungsgemeinschaft within Graduate School "Template-designed organic electronics (TIDE)"[GRK 2591] ; BMBF[FKZ: 13 N13637] ; DFG[RTG 2247] ; German Research Foundation DFG[FR 2833/79-1] ; National Nuclear Security Administration of U.S. Department of Energy[89233218CNA000001]
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Cited Times [WOS]:4
|Document Type||Journal Article|
|Department||Department of Materials Science and Engineering|
1.Institut für Physik,Carl von Ossietzky Universität,Oldenburg,26129,Germany
2.Bremen Center for Computational Materials Science,University of Bremen,Bremen,28359,Germany
3.Theoretical Division,Center for Integrated Nanotechnologies,Los Alamos National Laboratory,Los Alamos,87545,United States
4.Kekulé-Institute for Organic Chemistry and Biochemistry,University of Bonn,Bonn,53121,Germany
5.Department of Materials Science and Engineering,Southern University of Science and Technology,Shenzhen,Guangdong,518055,China
6.Center for Nanoscale Dynamics (CeNaD),Carl von Ossietzky Universität,Oldenburg,26129,Germany
7.Beijing Computational Science Research Center (CSRC),Beijing,100193,China
8.Shenzhen Computational Science and Applied Research (CSAR) Institute,Shenzhen,518110,China
9.Forschungszentrum Neurosensorik,Carl von Ossietzky Universität,Oldenburg,26129,Germany
Timmer，Daniel,Zheng，Fulu,Gittinger，Moritz,et al. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes[J]. Journal of the American Chemical Society,2022.
Timmer，Daniel.,Zheng，Fulu.,Gittinger，Moritz.,Quenzel，Thomas.,Lünemann，Daniel C..,...&Lienau，Christoph.(2022).Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes.Journal of the American Chemical Society.
Timmer，Daniel,et al."Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes".Journal of the American Chemical Society (2022).
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