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2020 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 142, no 32, p. 13941-13953Article in journal (Refereed) Published
Abstract [en]
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.
Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
Keywords
Aromatic compounds, Photocyclization, Excited states, Molecular switches, Quantum chemical calculations, Molecular dynamics simulations, Organic synthesis
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-167809 (URN)10.1021/jacs.0c06327 (DOI)000562942200035 ()
Funder
Stiftelsen Olle Engkvist Byggmästare, 184-568 and 204-0183Swedish Research Council, 2019-03664
Note
Funding agenceis: Olle Engkvist Foundation [184-568, 204-0183]; Swedish Research CouncilSwedish Research Council [2019-03664]; Hungarian Academy of Sciences through the Lendulet Program [LENDULET_2018_355]; National Research, Development and Innovation Office, Hungary (NKF
2020-07-292020-07-292020-09-12