Electrochemical and spectroelectrochemical behavior of cobalt(III), cobalt(II), and cobalt(I) complexes of meso-tetraphenylporphyrinate bearing bromides on the .beta.-pyrrole positions

D’Souza, Francis; Villard, Anne; Caemelbecke, Eric Van; Franzen, M. M.; Boschi, T.; Tagliatesta, Pietro; Kadish, Karl M.

doi:10.1021/ic00071a012

Cited by 144 publications

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“…1). Our finding is in agreement with available literature on the effect of ␤-bromination on the E1 ⁄2 of metalloporphyrins (41)(42)(43)(44)(45)(46)(47)). An almost identical increase in E1 ⁄2 (508 mV) was achieved by placing four quaternized ortho-pyridyls in the meso positions of the Mn III T-2-PyP ϩ .…”

Section: Electrostatics Versus Redox Potential In the Catalysis Of Osupporting

confidence: 93%

“…The electron-withdrawing effect of the ␤-pyrrolic bromines on the redox properties of the metal center of the porphyrins (50 -70 mV/bromine) has been previously established (41)(42)(43)(44)(45)(46)(47). The effect of eight ␤-pyrrolic bromines was expected to be similar in magnitude to the effect of the four quaternized pyridyl nitrogens on the redox properties of the starting unsubstituted Mn III T-2-PyP ϩ porphyrin molecule.…”

mentioning

confidence: 88%

“…Thus it was possible to determine the halfwave potentials, E1 ⁄2 , given in Table I. The two compounds have almost identical Mn II /Mn III metal-centered E1 ⁄2 values at pH 7.8, as predicted from the number and the nature of the electron-withdrawing substituents on the meso positions of the porphyrin ring (41)(42)(43)(44)(45)(46)(47). Moreover, their voltammetric behavior in terms of electrochemical reversibility (peak-to-peak potential separation, ⌬E pp ( Fig.…”

Section: Electrochemistrymentioning

confidence: 99%

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Electrostatic Contribution in the Catalysis of O 2·_Dismutation by Superoxide Dismutase Mimics

Spasojević

Batinić‐Haberle

Rebouças

et al. 2003

Journal of Biological Chemistry

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The Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)-porphyrin (Mn III TE-2-PyP 5؉ ) is a potent superoxide dismutase (SOD) mimic in vitro and was beneficial in rodent models of oxidative stress pathologies. Its high activity has been ascribed to both the favorable redox potential of its metal center and to the electrostatic facilitation assured by the four positive charges encircling the metal center. (ϩ890 mV versus NHE). Thus it allows equal driving force (hence k ox ϭ k red ϭ ϳ2 ϫ 10 9 M Ϫ1 s Ϫ1 ) for both half-reactions of the catalytic cycles (Reactions 1 and 2) (18 -20). For Escherichia coli Fe-SOD,the E1 ⁄2 is ϩ223 mV versus NHE at pH 7.4, and for Mn-SOD from the Bacillus stearothermophilus and E. coli the E1 ⁄2 were ϩ260 and ϩ310 mV versus NHE at pH 7 (1, 21, 22). However, when manganese was replaced by iron in the active site of Mn-SOD the enzymatic activity was lost (18), which has been attributed to the decrease of the redox potential below that required for the oxidation of superoxide ion (3, 18). Such metal ion specificity (2) has been recently explained by the higher affinity of Fe 3ϩ than Mn 3ϩ for hydroxide (6, 8).The crystal structures of different SODs reveal a highly conserved electrostatic "funnel" (13,14,16) that is believed to guide the negatively charged superoxide toward the active site of the enzyme. In the past there have been considerable efforts to evaluate the extent of electrostatic facilitation, but a major difficulty lies in the inability to specifically modify the positively charged residues without affecting the structural integrity of the active site (9).The Mn(III) porphyrin, Mn III TE-2-PyP 5ϩ (AEOL-10113) has been shown (23-27) to possess high SOD-like activity in vitro * This work was supported in part by Grant BA1-0103-1 from the Christopher Reeve Paralysis Foundation and by Aeolus/Incara Pharmaceuticals, Research Triangle Park, NC. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.§ To whom correspondence should be addressed. 1 The abbreviations used are: NHE, normal hydrogen electrode; SOD, superoxide dismutase; meso, refers to the substituents at the 5, 10, 15, and 20 (meso carbon) position of the porphyrin core; ␤, refers to the substituents at ␤-pyrrolic carbons; Mn III T-2-PyP ϩ , Mn(III) 5,10,-15,20-tetrakis(2-pyridyl)porphyrin; Mn III TE-2-PyP 5ϩ (Mn-2E 5ϩ ) (AEOL-10113), manganese(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin; Mn III TM-2(3,4)-PyP 5ϩ (Mn-2(3,4)M 5ϩ ), manganese(III) 5,10,15,20-tetrakis(N-methylpyridinium-2(3,4)-yl)porphyrin, where 2 (AEOL-10112), 3, and 4 refer to ortho, meta, and para isomers, respectively; Mn III Br 8 T-2-PyP ϩ (Mn-Br 8 ϩ ), Mn(III) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2-pyridyl)porphyrin; Mn II Br 8 TM-4-PyP 4ϩ , Mn(II) 2,3,7,8,12,13,17,10,15,porphyrin; Mn II Cl 5 TE-2-PyP 4ϩ , Mn(II) ␤-pentachloro-5,10,15,20-tetrakis(N-ethylpyridi...

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Section: Electrostatics Versus Redox Potential In the Catalysis Of Osupporting

confidence: 93%

mentioning

confidence: 88%

Section: Electrochemistrymentioning

confidence: 99%

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Electrostatic Contribution in the Catalysis of O 2·_Dismutation by Superoxide Dismutase Mimics

Spasojević

Batinić‐Haberle

Rebouças

et al. 2003

Journal of Biological Chemistry

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“…In order to corroborate this assumption, controlled potential electrolysis was carried out at 0.3 V. The comparison of the UV-visible spectra of the cobalt complex recorded before and after the complete electrolysis shows the disappearance of the Soret band (λ = 390 nm) while another band appears at λ =416 nm. As previously described for cobalt complexes, this red shift confirms that the one-electron oxidation occurs at the metal center [20][21][22]. It should be noted that the Co(II)/Co(III) transition occurs at a markedly less positive potential value than the half-wave potential values commonly observed for the generation of Co(III) porphyrins.…”

Section: Electroactivity Of the Complexes 1 Andsupporting

confidence: 87%

“…•-) [20]. Rotating disk experiments indicated identical values for the current recorded at the first and second reduction process corroborating thus the monoelectronic character of the second reduction.…”

Section: Electroactivity Of the Complexes 1 Andsupporting

confidence: 54%

A poly(pyrrole-Cobalt(II)deuteroporphyrin) electrode for the potentiometric determination of nitrite

Cosnier

Gondran

Wessel

et al. 2003

Sensors

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Abstract:The electrochemical properties of a new Co(II) deuteroporphyrin substituted by two electropolymerizable pyrrole groups has been investigated in organic solvent. This functionalization has allowed the preparation of the first example of a cobalt deuteroporphyrin film by oxidative electropolymerization. The resulting conducting polypyrrole film exhibits the regular electroactivity of cobalt deuteroporphyrin. Compared to conventional cobalt porphyrin electrochemistry, the replacement of porphyrin macrocycle by deuteroporphyrin ring results in markedly more negative potential values for the metalcentered oxidation and reduction processes. The influence of NO 2 -as axial ligand on the reductive behavior of the electropolymerized cobalt (II) deuteroporphyrin is examined. The recognition properties of the film illustrated by the potentiometric shift of the Co(II)/(I) reduction were exploited for the determination of NO 2 -in the concentration range 2 10 -6 -2.5 10 -4 M.

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Structural stabilities of water‐soluble MnTDCSPP, MnTSPP, and supported analogues toward hydrogen peroxide and sodium hypochlorite

Türk

Berber

2000

Int. J. Chem. Kinet.

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This article describes the structural stabilities of 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphinatomanganese(III) X (X: H 2 O) (MnTDCSPP), 5,10,15,20-Ϫ OH , tetra(4-sulfonatophenyl)porphinatomanganese(III) X (X: H 2 O) (MnTSPP) and their sup-Ϫ OH , ported analogues toward H 2 O 2 and NaOCl or HOCl depending on pH. The supports employed were hexadecyltrimethylammonium bromide (CTAB), 2,6-ionene, 2,10-ionene and a poly(vinylbenzyltrimethylammonium chloride) latex, which all contain quaternary ammonium groups. In the strong basic medium, both manganese porphyrins showed high stabilities toward NaOCl but relatively lower stabilities toward H 2 O 2 , and the resistance of MnTDCSPP to degradation was higher than that of MnTSPP. In the acidic solution, both porphyrins showed increasing stabilities toward H 2 O 2 as the pH went down. Toward HOCl, MnTSPP did not show any stability in the neutral and acidic solutions, whereas MnTDCSPP showed some. The supports made some influence on their stabilities. In general, the ionenes affected their stabilities adversely, and the latex and CTAB did positively. Especially when they were bound to CTAB, they were not degraded by H 2 O 2 atThe pseudo-first-order degradation rate constants pH Ͻ 2. of MnTDCSPP, MnTSPP, and their supported analogues at different pHs at 30ЊC were determined.

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Electrochemical and spectroelectrochemical behavior of cobalt(III), cobalt(II), and cobalt(I) complexes of meso-tetraphenylporphyrinate bearing bromides on the .beta.-pyrrole positions

Cited by 144 publications

References 0 publications

Electrostatic Contribution in the Catalysis of O 2·_Dismutation by Superoxide Dismutase Mimics

Electrostatic Contribution in the Catalysis of O 2·_Dismutation by Superoxide Dismutase Mimics

A poly(pyrrole-Cobalt(II)deuteroporphyrin) electrode for the potentiometric determination of nitrite

Structural stabilities of water‐soluble MnTDCSPP, MnTSPP, and supported analogues toward hydrogen peroxide and sodium hypochlorite

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