Protonation-coupled redox reactions in planar antiaromatic meso-pentafluorophenyl-substituted o-phenylene-bridged annulated rosarins

Masatoshi Ishida, Soo Jin Kim, Christian Preihs, Kei Ohkubo, Jong Min Lim, Byung Sun Lee, Jung Su Park, Vincent M. Lynch, Vladimir V. Roznyatovskiy, Tridib Sarma, Pradeepta K. Panda, Chang Hee Lee, Shunichi Fukuzumi, Dongho Kim, Jonathan L. Sessler

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101 Scopus citations


Proton-coupled electron transfer (PCET) processes are among the most important phenomena that control a variety of chemical and biological transformations. Although extensively studied in a variety of natural systems and discrete metal complexes, PCET mechanisms are less well codified in the case of purely organic compounds. Here we report that a planar β,β′- phenylene-bridged hexaphyrin (, a 24 π-electron antiaromatic species termed rosarin, displays unique redox reactivity on protonation. Specifically, treatment with acid (for example, HI) yields a 26 π-electron aromatic triprotonated monocationic species that is produced spontaneously via an intermediate - but stable - 25 π-electron non-aromatic triprotonated monoradical dication. This latter species is also produced on treatment of the original 24 π-electron antiaromatic starting material with HCl or HBr. The stepwise nature of the proton-coupled reduction observed in the planar rosarin stands in marked contrast to that seen for non-annulated rosarins and other ostensibly antiaromatic expanded porphyrinoids.

Original languageEnglish
Pages (from-to)15-20
Number of pages6
JournalNature Chemistry
Issue number1
StatePublished - Jan 2013

Bibliographical note

Funding Information:
Support is acknowledged from the US National Science Foundation (CHE-1057904 to J.L.S.), the Robert A. Welch Foundation (F-1018 to J.L.S.), Grant-in-Aid (No. 20108010 to S.F. and 23750014 to K.O.) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, the World Class University Program (R32-2010-000-10217-0 to D.K. and R31-2008-000-10010-0 to S.F.) of the Ministry of Education, Science and Technology, the Basic Science Research Programs, National Research Foundation (2009-0087013 to C-H.L), BK21, Council of Scientific and Industrial Research, India (from a senior research fellowship to T.S.) and the Department of Science and Technology India (SR/S1/IC-20/2007 to P.K.P.).


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