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Fakis M, Petropoulos V, Hrobárik P, Nociarová J, Osuský P, Maiuri M, Cerullo G. Exploring Solvent and Substituent Effects on the Excited State Dynamics and Symmetry Breaking of Quadrupolar Triarylamine End-Capped Benzothiazole Chromophores by Femtosecond Spectroscopy. J Phys Chem B 2022; 126:8532-8543. [PMID: 36256786 DOI: 10.1021/acs.jpcb.2c03103] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We investigate herein the excited state dynamics and symmetry breaking processes in three benzothiazole-derived two-photon absorbing chromophores by femtosecond fluorescence and transient absorption (fs-TA) spectroscopies in solvents of various polarity. The chromophores feature a quasi-quadrupolar D-π-A-π-D architecture comprised of an electron-withdrawing benzothiazole core and lateral triphenylamine donors (Qbtz-H), while the acceptor strength of the central unit is enforced by attached cyano groups (Qbtz-CN) and the electron-donating strength of the arylamine moieties by introduction of peripheral methoxy groups (Qbtz'-CN). Steady state spectroscopy reveals positive solvatochromism, which is mostly pronounced for Qbtz'-CN. Femtosecond spectroscopy of Qbtz-H reveals the coexistence of the Franck-Condon (FC) state and states populated after symmetry breaking (SB) in low-polarity solvents such as toluene and tetrahydrofuran, while the SB state becomes favorable in polar acetonitrile. For the other two molecules possessing a stronger electron-accepting unit and thus more polar excited state, SB takes place even in low-polarity solvents, as shown by fs-TA spectroscopy. Global fitting of the fs-TA spectra together with investigation of the evolution associated spectra (EAS) reveals the existence of an initial FC state in Qbtz-H, in all studied solvents, which relaxes toward Intermediate Charge Transfer (I-CT) and SB states. On the other hand, for Qbtz-CN and Qbtz'-CN in more polar solvents, the FC state undergoes ultrafast relaxation toward symmetry-broken charge transfer (SB-CT) states which in turn show very fast recombination to the ground state. Our measurements confirm that the extent of symmetry breaking is larger for D-π-A-π-D systems with the stronger acceptor core and increases further by increasing electron-donating strength of triarylamine moieties, giving rise to symmetry breaking in these nonionic quadrupolar molecules with ethynylene (triple bond) π-spacers also in less polar solvents.
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Affiliation(s)
- Mihalis Fakis
- Department of Physics, University of Patras, PatrasGR-26500, Greece
| | - Vasilis Petropoulos
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133Milan, Italy
| | - Peter Hrobárik
- Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, SK-84215Bratislava, Slovakia
| | - Jela Nociarová
- Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, SK-84215Bratislava, Slovakia
| | - Patrik Osuský
- Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, SK-84215Bratislava, Slovakia
| | - Margherita Maiuri
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133Milan, Italy
| | - Giulio Cerullo
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133Milan, Italy
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Li C, Adler C, Krivtsov I, Mitoraj D, Leiter R, Kaiser U, Beranek R, Dietzek B. Ultrafast anisotropic exciton dynamics in a water-soluble ionic carbon nitride photocatalyst. Chem Commun (Camb) 2021; 57:10739-10742. [PMID: 34585184 DOI: 10.1039/d1cc03812e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ultrafast transient absorption anisotropy spectroscopy (TAA) reveals the orientational dynamics of light-induced excitations in a water soluble poly(heptazine imide). The results provide insights into the fast charge transfer processes in the material.
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Affiliation(s)
- Chunyu Li
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, Jena 07743, Germany. .,Leibniz Institute of Photonic Technology (Leibniz-IPHT), Research Department Functional Interfaces, Albert-Einstein-Strasse 9, Jena 07745, Germany
| | - Christiane Adler
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany.
| | - Igor Krivtsov
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany.
| | - Dariusz Mitoraj
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany.
| | - Robert Leiter
- Central Facility for Electron Microscopy, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany
| | - Ute Kaiser
- Central Facility for Electron Microscopy, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany
| | - Radim Beranek
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, Ulm 89081, Germany.
| | - Benjamin Dietzek
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, Jena 07743, Germany. .,Leibniz Institute of Photonic Technology (Leibniz-IPHT), Research Department Functional Interfaces, Albert-Einstein-Strasse 9, Jena 07745, Germany.,Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, Jena 07743, Germany
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