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Article: Novel osmium(IV) and -(V) porphyrins. Synthesis, spectroscopy, and electrochemistry

TitleNovel osmium(IV) and -(V) porphyrins. Synthesis, spectroscopy, and electrochemistry
Authors
Issue Date1990
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/ic
Citation
Inorganic Chemistry, 1990, v. 29 n. 10, p. 1841-1846 How to Cite?
AbstractReduction of [OsVI(P)(O)2] (P = porphyrin dianion) with PPh3, ascorbic acid, or N2H4·H2O in the presence of ROH and RSH yielded [OsIV(P)(OR)2] and [OsIV(P)(SR)2], respectively. [OsIV(OEP)Br2] (H2OEP = octaethylporphyrin) was prepared from [OsVI(OEP)(O)2] and Br2. The dialkoxyosmium(IV) and dibromoosmium(IV) porphyrin complexes are paramagnetic with measured μeff values of 2.27-2.79 μB. which are close to the spin-only values for two unpaired electrons and independent of temperature from -30 to 30°C. The [OsIV(P)(SR)2] species are diamagnetic, suggesting that the RS- ligand is a poor π-donor. The 1H NMR spectral data for the paramagnetic [OsIV(P)(OR)2] and [OsIV(P)Br2] complexes are discussed. For the [OsIV(p-X-TPP)(OEt)2] system [H2(p-X-TPP) = para-substituted tetraphenylporphyrin], the relative isotopic shifts of the phenyl protons are mainly due to dipolar interactions. A large ring current effect on the methine C-H and pyrrolic methylene protons of [OsIV(OEP)X2] has been found. Except for [OsIV(P)(SR)2], the osmium(IV) porphyrins exhibit reversible Os(IV/III) and Os(V/IV) couples. For [OsIV(P)X2], the redox potentials of Os(IV/III) couples decrease in the order of X = Br > PhO > PhS > MeO, EtO > i-PrO. [OsIV(OEP)(OEt)2] can be oxidized to [OsV(OEP)(OEt)2]+ at a potential of 0.13 V vs Cp2Fe+/0. For the [OsIV(p-X-TPP)(OEt)2] system, the redox potentials of Os(V/IV) couples, which lie between 0.27 and 0.37 V, show a linear free energy relationship with the 4σ constants of the para substituents on the four phenyl rings. Oxidation of [OsIV(OEP)(OEt)2] and [OsIV(TPP)(OEt)2] gave the respective [OsV(OEP)(OEt)2]+ and [OsV(TPP)(OEt)2]+, characterized by UV-vis spectroscopy. © 1990 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/167383
ISSN
2015 Impact Factor: 4.82
2015 SCImago Journal Rankings: 1.873
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DC FieldValueLanguage
dc.contributor.authorChe, CMen_US
dc.contributor.authorLeung, WHen_US
dc.contributor.authorChung, WCen_US
dc.date.accessioned2012-10-08T03:06:18Z-
dc.date.available2012-10-08T03:06:18Z-
dc.date.issued1990en_US
dc.identifier.citationInorganic Chemistry, 1990, v. 29 n. 10, p. 1841-1846en_US
dc.identifier.issn0020-1669en_US
dc.identifier.urihttp://hdl.handle.net/10722/167383-
dc.description.abstractReduction of [OsVI(P)(O)2] (P = porphyrin dianion) with PPh3, ascorbic acid, or N2H4·H2O in the presence of ROH and RSH yielded [OsIV(P)(OR)2] and [OsIV(P)(SR)2], respectively. [OsIV(OEP)Br2] (H2OEP = octaethylporphyrin) was prepared from [OsVI(OEP)(O)2] and Br2. The dialkoxyosmium(IV) and dibromoosmium(IV) porphyrin complexes are paramagnetic with measured μeff values of 2.27-2.79 μB. which are close to the spin-only values for two unpaired electrons and independent of temperature from -30 to 30°C. The [OsIV(P)(SR)2] species are diamagnetic, suggesting that the RS- ligand is a poor π-donor. The 1H NMR spectral data for the paramagnetic [OsIV(P)(OR)2] and [OsIV(P)Br2] complexes are discussed. For the [OsIV(p-X-TPP)(OEt)2] system [H2(p-X-TPP) = para-substituted tetraphenylporphyrin], the relative isotopic shifts of the phenyl protons are mainly due to dipolar interactions. A large ring current effect on the methine C-H and pyrrolic methylene protons of [OsIV(OEP)X2] has been found. Except for [OsIV(P)(SR)2], the osmium(IV) porphyrins exhibit reversible Os(IV/III) and Os(V/IV) couples. For [OsIV(P)X2], the redox potentials of Os(IV/III) couples decrease in the order of X = Br > PhO > PhS > MeO, EtO > i-PrO. [OsIV(OEP)(OEt)2] can be oxidized to [OsV(OEP)(OEt)2]+ at a potential of 0.13 V vs Cp2Fe+/0. For the [OsIV(p-X-TPP)(OEt)2] system, the redox potentials of Os(V/IV) couples, which lie between 0.27 and 0.37 V, show a linear free energy relationship with the 4σ constants of the para substituents on the four phenyl rings. Oxidation of [OsIV(OEP)(OEt)2] and [OsIV(TPP)(OEt)2] gave the respective [OsV(OEP)(OEt)2]+ and [OsV(TPP)(OEt)2]+, characterized by UV-vis spectroscopy. © 1990 American Chemical Society.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/icen_US
dc.relation.ispartofInorganic Chemistryen_US
dc.titleNovel osmium(IV) and -(V) porphyrins. Synthesis, spectroscopy, and electrochemistryen_US
dc.typeArticleen_US
dc.identifier.emailChe, CM:cmche@hku.hken_US
dc.identifier.authorityChe, CM=rp00670en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/ic00335a016-
dc.identifier.scopuseid_2-s2.0-0004847937en_US
dc.identifier.volume29en_US
dc.identifier.issue10en_US
dc.identifier.spage1841en_US
dc.identifier.epage1846en_US
dc.identifier.isiWOS:A1990DD99500016-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridChe, CM=7102442791en_US
dc.identifier.scopusauthoridLeung, WH=7201504510en_US
dc.identifier.scopusauthoridChung, WC=15082221200en_US

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