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Unraveling Excited-Singlet-State Aromaticity via Vibrational Analysis
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2017 (English)In: Chem, ISSN 24519294, Vol. 3, no 5, p. 870-880Article in journal (Refereed) Published
Abstract [en]

Summary

The concept of excited-state aromaticity is receiving much attention in that completely reversed aromaticity in the excited state (so-called aromaticity reversal) provides crucial insight into photostability, photoreactivity, and its application to the photosynthetic mechanism and photoactive materials. Despite this significance, experimental elucidation of excited-state aromaticity is still unsolved, particularly for the excited singlet state. Here, as an unconventional approach, time-resolved IR (TRIR) spectroscopy on aromatic and anti-aromatic hexaphyrin congeners shed light on excited-singlet-state aromaticity. The contrasting spectral features between the Fourier transform IR and TRIR spectra reveal the aromaticity-driven structural changes, corroborating aromaticity reversal in the excited singlet states. Our paradigm for excited-state aromaticity, the correlation of IR spectral features with aromaticity reversal, provides another fundamental key to understanding the role of (anti)aromaticity in the stability, dynamics, and reactivity in the excited singlet state of π-conjugated molecular systems.

Place, publisher, year, edition, pages
2017. Vol. 3, no 5, p. 870-880
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-349223DOI: 10.1016/j.chempr.2017.09.005OAI: oai:DiVA.org:uu-349223DiVA, id: diva2:1200095
Funder
Swedish Research Council, 2015-04538Available from: 2018-04-23 Created: 2018-04-23 Last updated: 2018-05-16Bibliographically approved
In thesis
1. Influence of Aromaticity on Excited State Structure, Reactivity and Properties
Open this publication in new window or tab >>Influence of Aromaticity on Excited State Structure, Reactivity and Properties
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes work that could help development of new photochemical reactions and light-absorbing materials. Focus is on the chemical concept "aromaticity" which is a proven conceptual tool in developing thermal chemical reactions. It is here shown that aromaticity is also valuable for photochemistry. The influence of aromaticity is discussed in terms of structure, reactivity and properties. With regard to structure, it is found that photoexcited molecules change their structure to attain aromatic stabilization (planarize, allow through-space conjugation) or avoid antiaromatic destabilization (pucker). As for reactivity, it is found that stabilization/destabilization of reactants decrease/increase photoreactivity, in accordance with the Bell-Evans-Polanyi relationship. Two photoreactions based on excited state antiaromatic destabilization of the substrates are reported. Finally, with respect to properties, it is shown that excited state energies can be tuned by considering aromatic effects of both the electronic ground state and the electronically excited states. The fundamental research presented in this thesis forms a foundation for the development of new photochemical reactions and design of compounds for new organic electronic materials.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 55
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1679
Keywords
photochemistry, aromaticity, computational chemistry
National Category
Organic Chemistry Theoretical Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-349229 (URN)978-91-513-0354-3 (ISBN)
Public defence
2018-06-14, room 80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-05-22 Created: 2018-04-23 Last updated: 2018-05-22

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Jorner, KjellOttosson, Henrik

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