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Formation of Ground State Triplet Diradicals from Annulated Rosarin Derivatives by Triprotonation

Title
Formation of Ground State Triplet Diradicals from Annulated Rosarin Derivatives by Triprotonation
Authors
Fukuzumi, ShunichiOhkubo, KeiIshida, MasatoshiPreihs, ChristianChen, BoBorden, Weston ThatcherKim, DonghoSessler, Jonathan L.
Ewha Authors
Shunichi FukuzumiKei Okubo
SCOPUS Author ID
Shunichi Fukuzumiscopus; Kei Okuboscopus
Issue Date
2015
Journal Title
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
ISSN
0002-7863JCR Link
Citation
vol. 137, no. 31, pp. 9780 - 9783
Publisher
AMER CHEMICAL SOC
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Annulated rosarins, beta,beta-bridged hexaphyrin(1.0.1.0.1.0) derivatives 1-3, are formally 24 pi-electron antiaromatic species. At low temperature, rosarins 2 and 3 are readily triprotonated in the presence of trifluoroacetic acid in dichloromethane to produce ground state triplet diradicals, as inferred from electron paramagnetic resonance (EPR) spectral studies. From an analysis of the fine structure in the EPR spectrum of triprotonated rosarin H(3)3(3+), a distance of 3.6 angstrom between the two unpaired electrons was estimated. The temperature dependence of the singlet-triplet equilibrium was determined by means of an EPR titration. Support for these experimental findings came from calculations carried out at the (U)B3LYP/6-31G* level, which served to predict a very low-lying triplet state for the triprotonated form of a simplified model system 1.
DOI
10.1021/jacs.5b05309
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자연과학대학 > 화학·나노과학전공 > Journal papers
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