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• 作者：Ivan Spasojevi//pubs.acs.org/images/entities/cacute.gif" border="0"> ; Ramil Menzeleev ; Peter S. White ; and Irwin Fridovich
• 刊名：Inorganic Chemistry
• 出版年：2002
• 出版时间：November 4, 2002
• 年：2002
• 卷：41
• 期：22
• 页码：5874 - 5881
• 全文大小：154K
• 年卷期：v.41,no.22(November 4, 2002)
• ISSN：1520-510X

文摘

Rotational (atropo-) isomers of Mn(III) meso-tetrakis(N-alkylpyridinium-2-yl)porphyrins and corresponding metal-free porphyrin ligands (where alkyl is methyl, ethyl, n-butyl, n-hexyl) and Zn(II) meso-tetrakis(N-methyl(ethyl,n-hexyl)pyridinium-2-yl)porphyrins were separated and isolated by reverse-phase HPLC. The identity of the rotationalisomers of metal-free meso-tetrakis(N-methylpyridinium-2-yl)porphyrin was established by ¹H NMR spectra and bythe crystal structure of the fastest eluting fraction (R_f = 7.7%, R_w = 9.2%, P2₁/c, Z = 8, a = 14.2846(15) Å, b= 22.2158(24) Å, c = 29.369(3) Å, ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 95.374(2)ages/entities/deg.gif">) which, in accordance with ¹H NMR interpretation, proved tobe the ages/gifchars/alpha.gif" BORDER=0>ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">ages/gifchars/alpha.gif" BORDER=0>ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> isomer. This result, together with elution intensity patterns, was used to identify the fractions of otherMn(III)-porphyrins, Zn(II)-porphyrins, and corresponding metal-free ligands in the series. All of the atropoisomerswere inert toward isomerization which was not observable for 30 days at room temperature and reached only 50%in 16 days at 90 ages/entities/deg.gif">C in the case of the Mn(III)-ethyl analogue. However, a complete freeze-dry removal of themobile phase from the HPLC fractions caused an almost 100% isomerization. The Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin, as a mixture of atropoisomers (AEOL-10113), has been shown to offer protection inoxidative stress injury ascribed to its high reactivity toward superoxide (k_cat = 5.8 × 10⁷ M^-1 s^-1) as a consequenceof its favorable redox potential (E_1/2 = +228 mV vs NHE). In this work, the atropoisomers were found to havesimilar redox potentials ranging from +240 to +220 mV, to be similarly potent catalysts of O₂^{ages/entities/bull.gif">-} disproportionation(dismutation), with k_cat ranging from 5.5 × 10⁷ to 6.8 × 10⁷ M^-1 s^-1, and not to preferentially bind to biologicaltissue.