Facile Supramolecular Engineering of Porphyrin cis Tautomers: The Case of beta-Octabromo-meso-tetraarylporphyrins

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dc.contributor.authorThomas, Kolle E.en
dc.contributor.authorSlebodnick, Carlaen
dc.contributor.authorGhosh, Abhiken
dc.contributor.departmentChemistryen
dc.date.accessioned2020-08-28T13:23:23Zen
dc.date.available2020-08-28T13:23:23Zen
dc.date.issued2020-04-21en
dc.description.abstractA porphyrin cis tautomer, where the two central NH protons are on adjacent pyrrole rings, has long been invoked as an intermediate in porphyrin tautomerism. Only recently, however, has such a species been isolated and structurally characterized. Thus, single-crystal X-ray structure determinations of two highly saddled free-base porphyrins, beta-heptakis(trifluoromethyl)-mesotetrakis(p-fluorophenyl)porphyrin, H-2[(CF3)(7)TFPP], and beta-octaiodo- 5,10,15,20- tetrakis(4'-trifluoromethylphenyl) porphyrin, H-2[I8TCF3PP], unambiguously revealed cis tautomeric structures, each stabilized as a termolecular complex with a pair of ROH (R = CH3 or H) molecules that form hydrogen-bonded N-H center dot center dot center dot O-H center dot center dot center dot N straps connecting the central NH groups with the antipodal unprotonated nitrogens. The unusual substitution patterns of these two porphyrins, however, have left open the question how readily such supramolecular assemblies might be engineered, which prompted us to examine the much more synthetically accessible beta-octabromo-meso-tetraphenylporphyrins. Herein, single-crystal Xray structures were obtained for two such compounds, 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4'-trifluoromethylphenyl)porphyrin, H-2[Br8TCF3PP], and 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4'-fluorophenyl)porphyrin, H-2[Br8TFPP], and although the central hydrogens could not all be located unambiguously, the electron density could be convincingly modeled as porphyrin cis tautomers, existing in each case as a bis-methanol adduct. In addition, a perusal of the Cambridge Structural Database suggests that there may well be additional examples of porphyrin cis tautomers that have not been recognized as such. We are therefore increasingly confident that porphyrin cis tautomers are readily accessible via supramolecular engineering, involving the simple stratagem of crystallizing a strongly saddled porphyrin from a solvent system containing an amphiprotic species such as water or an alcohol.en
dc.description.notesThis work was supported by the Research Council of Norway (grant no. 262229) and the U.S. National Science Foundation (grant no. CHE-1726077). We thank Dr. Laura J. McCormickMcPherson for helpful discussions.en
dc.description.sponsorshipResearch Council of NorwayResearch Council of Norway [262229]; U.S. National Science FoundationNational Science Foundation (NSF) [CHE-1726077]en
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1021/acsomega.0c00517en
dc.identifier.issn2470-1343en
dc.identifier.issue15en
dc.identifier.pmid32337452en
dc.identifier.urihttp://hdl.handle.net/10919/99866en
dc.identifier.volume5en
dc.language.isoenen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.titleFacile Supramolecular Engineering of Porphyrin cis Tautomers: The Case of beta-Octabromo-meso-tetraarylporphyrinsen
dc.title.serialACS Omegaen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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