| 1. |
- Kalapos, Peter Pal, et al.
(författare)
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Photoswitching of Local (Anti)Aromaticity in Biphenylene-Based Diarylethene Molecular Switches
- 2022
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 87:15, s. 9532-9542
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Tidskriftsartikel (refereegranskat)abstract
- Photoinduced tuning of (anti)aromaticity and associated molecular properties is currently in the focus of attention for both tailoring photochemical reactivity and designing new materials. Here, we report on the synthesis and spectroscopic characterization of diarylethene-based molecular switches embedded in a biphenylene structure composed of rings with different levels of local (anti)aromaticity. We show that it is possible to modulate and control the (anti)aromatic character of each ring through reversible photoswitching of the aryl units of the system between open and closed forms. Remarkably, it is shown that the irreversible formation of an annulated bis(dihydro-thiopyran) side-product that hampers the photoswitching can be efficiently suppressed when the aryl core formed by thienyl groups in one switch is replaced by thiazolyl groups in another.
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| 2. |
- Kalapos, Peter Pal, et al.
(författare)
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Salicylideneaniline/Dithienylethene Hybrid Molecular Switches: Design, Synthesis, and Photochromism
- 2023
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Ingår i: Journal of Organic Chemistry. - : AMER CHEMICAL SOC. - 0022-3263 .- 1520-6904. ; 89:1, s. 16-26
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid molecular switch comprising salicylideneaniline (SA) and dithienylethene (DTE) moieties around a single benzene ring is reported. Due to an interplay between solvent-assisted enol-keto tautomerization in the former moiety and photochromic electrocyclization in the latter, this dithienylbenzene derivative was found to be photoresponsive at room temperature with a thermally stable closed form. The main photoproduct featuring ring-closed DTE and keto-enamine SA structures could be isolated and converted back to the starting material by irradiation with visible light. The optical properties of the potential structures involved in the overall process were characterized by using density functional theory (DFT) calculations in good agreement with the measured data. The reversibility of the conversion could be tuned by the presence of donor and acceptor substituents, while the introduction of the imine in the form of a benzothiazole moiety enabled photochemistry even in nonprotic solvents.
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| 3. |
- Oruganti, Baswanth, et al.
(författare)
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Photoinduced Changes in Aromaticity Facilitate Electrocyclization of Dithienylbenzene Switches
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:32, s. 13941-13953
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Tidskriftsartikel (refereegranskat)abstract
- The concepts of excited-state aromaticity and antiaromaticity have in recent years with increasing frequency been invoked to rationalize the photochemistry of cyclic conjugated organic compounds, with the long-term goal of using these concepts to improve the reactivities of such compounds toward different photochemical transformations. In this regard, it is of particular interest to assess how the presence of a benzene motif affects photochemical reactivity, as benzene is well-known to completely change its aromatic character in its lowest excited states. Here, we investigate how a benzene motif influences the photoinduced electrocyclization of dithienylethenes, a major class of molecular switches. Specifically, we report on the synthesis of a dithienylbenzene switch where the typical nonaromatic, ethene-like motif bridging the two thienyl units is replaced by a benzene motif, and show that this compound undergoes electrocyclization upon irradiation with UV-light. Furthermore, through a detailed quantum chemical analysis, we demonstrate that the electrocyclization is driven jointly and synergistically by the loss of aromaticity in this motif from the formation of a reactive, antiaromatic excited state during the initial photoexcitation, and by the subsequent relief of this antiaromaticity as the reaction progresses from the Franck-Condon region. Overall, we conclude that photoinduced changes in aromaticity facilitate the electrocyclization of dithienylbenzene switches.
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