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π-Extension in Expanded Porphyrins: Cyclo[4]naphthobipyrrole
Roznyatovskiy, Vladimir V.,Lim, Jong Min,Lynch, Vincent M.,Lee, Byung Sun,Kim, Dongho,Sessler, Jonathan L. American Chemical Society 2011 ORGANIC LETTERS Vol.13 No.20
<P>The π-extended cyclo[4]naphthobipyrrole <B>1a</B> has been prepared <I>via</I> an Fe(III)-mediated oxidative cyclization of an alkyl-substituted naphthobipyrrole. The structure of this new expanded porphyrin, isolated as the deprotonated sulfate salt, was characterized by spectroscopic means, as well through a single crystal X-ray diffraction analysis. Salt <B>1a</B> displays a total of four well-resolved redox waves as determined by cyclic voltammetry. It also displays bathochromically shifted near-IR absorption maxima compared to the diprotonated forms of nonannulated cyclo[8]pyrroles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orlef7/2011/orlef7.2011.13.issue-20/ol2023449/production/images/medium/ol-2011-023449_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ol2023449'>ACS Electronic Supporting Info</A></P>
Zhang, Zhan,Lim, Jong Min,Ishida, Masatoshi,Roznyatovskiy, VladimirV.,Lynch, Vincent M.,Gong, Han-Yuan,Yang, Xiaoping,Kim, Dongho,Sessler, Jonathan L. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.9
<P>Novel hybrid cyclo[<I>m</I>]pyridine[<I>n</I>]pyrroles have been synthesized using Suzuki coupling.Their NMRand optical spectroscopic features and solid state structural parametersprovide support for the proposal that these species are best describedas locally aromatic compounds devoid of long-range intersubunit conjugation.However, an extension of the π-conjugation in the macrocyclescan be realized through protonation, as inferred from optical spectroscopicand X-ray diffraction-based structural studies.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-9/ja211985k/production/images/medium/ja-2011-11985k_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja211985k'>ACS Electronic Supporting Info</A></P>
Ishida, Masatoshi,Kim, Soo-Jin,Preihs, Christian,Ohkubo, Kei,Lim, Jong Min,Lee, Byung Sun,Park, Jung Su,Lynch, Vincent M.,Roznyatovskiy, Vladimir V.,Sarma, Tridib,Panda, Pradeepta K.,Lee, Chang-Hee,Fu Nature Publishing Group 2013 Nature chemistry Vol.5 No.1
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 棺,棺??phenylene-bridged hexaphyrin (1.0.1.0.1.0), a 24 ?-electron antiaromatic species termed rosarin, displays unique redox reactivity on protonation. Specifically, treatment with acid (for example, HI) yields a 26 ?-electron aromatic triprotonated monocationic species that is produced spontaneously via an intermediate??but stable??25 ?-electron non-aromatic triprotonated monoradical dication. This latter species is also produced on treatment of the original 24 ?-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.