A reinvestigation of silver porphyrin electrochemistry. Reactions of silver(III), silver(II), and silver(I)

Kadish, Karl M.; Lin, Xingguang; Ding, Jie; Wu, Yi; Araullo, C.

doi:10.1021/ic00238a029

Cited by 36 publications

(34 citation statements)

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“…11 Collman et al reported in 1983 the use of NaBH 4 as an efficient demetalation reagent for silver porphyrins, 18 and its reducing mechanism was elucidated by Cowan and Sanders 19 a few years later. Following a slightly modified protocol, we demetalated (T tBu PCor)Ag by treatment of the complex with excess NaBH 4 in a CH 2 Cl 2 /CH 3 OH solution at room temperature.…”

Section: Resultsmentioning

confidence: 99%

“…The investigated compounds are shown in Chart 1. Because a reduction mechanism is presumably involved in the demetalation process, in analogy with silver porphyrins, 11 we have performed electrochemical studies on both the silver triarycorrolates and the corresponding nitro derivatives to elucidate the redox processes involved and have spectrally characterized the corrole demetalation product after controlled potential reduction in a thin-layer cell.…”

Section: Introductionmentioning

confidence: 99%

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Demetalation of Silver(III) Corrolates

et al. 2009

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Several procedures for the demetalation of silver(III) corrolates have been tested. Acidic conditions induce removal of the silver ion but they can also promote concomitant oxidation of the corrole nucleus to an isocorrole species, the degree of which will depend upon the specific acidic media. This oxidation cannot be completely avoided by addition of hydrazine, particularly in the case of 3-NO2 substituted complexes which are quantitatively converted into the corresponding 3-NO2, 5-hydroxy isocorroles upon silver ion removal. Several β-nitro isocorrole products were isolated, and one was structurally characterized. Electrochemical and chemical reductive methods for silver(III) corrolates demetalation were then tested with the aim to avoid the formation of isocorroles. While reaction with sodium borohydride was shown to be quite effective to demetalate unsubstituted silver corrolates this was not the case for the β-nitro derivatives where the peripheral nitro group is reduced by borohydride giving the corresponding 3-amino free base corrole species. For the β-nitro corrole silver complexes, a successful approach was obtained using DBU/THF solutions which afforded the 3-NO2 corrole free-base compound as a single reaction product in good yield. These conditions were also effective for unsubstituted corroles although longer reaction times were necessary in this case. To study in greater detail the corrole demetalation behavior, selected Ag(III) derivatives were characterized by cyclic voltammetry in pyridine, and the demetalation products spectrally characterized after controlled potential reduction in a thin-layer spectroelectrochemical cell.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Demetalation of Silver(III) Corrolates

et al. 2009

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“…All three reactions involve reversible one-electron transfers located at E 1/2 ) 0.72, 1.20, and -0.87 V vs SCE. 23 The electrochemical data in Figure 3a can be compared to results obtained for (TPP)Ag II under similar solution conditions, 24 where TPP ) the dianion of tetraphenylporphyrin. The (TPP)Ag II complex is reduced to its Ag(I) form at -1.01 V vs SCE in CH 2 Cl 2 and oxidized to [(TPP)Ag III ] + at 0.59 V. Both reactions of the porphyrin occur at more negative potentials than those for the reduction and oxidation of (TtBuPCor)Ag III , but the HOMO-LUMO gap of 1.60 V for (TPP)Ag II is identical within experimental error to the 1.59 V gap observed in the case of (TtBuPCor)Ag III .…”

Section: Resultsmentioning

confidence: 99%

Functionalization of Corroles: The Nitration Reaction

et al. 2007

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The reaction of meso-triarylcorroles with AgNO2 proceeds with concomitant metalation and peripheral substitution to give the corresponding nitro-substituted silverIII corrole complex. The substitution is highly regioselective, giving only the corresponding 3-nitro derivative, among the different possible isomers. The results obtained indicate that the reaction intermediate is the pi-cation radical of the complex, which is then attacked by nitrite ion. This was proven by the reaction of the copper corrole complexes with NaNO2: in this case, the nitration reaction proceeded without the addition of an oxidant, because of the pi-cation radical character of the copper complex. The reaction is also successful in the case of 2,3,17,18-tetraethyl-8,12-diacetoxymethyl-7,13-dimethylcorrole (AMCorH3), with the formation of the meso-substituted silver corrole derivative (NO2)3AMCorAg (fully characterized by X-ray crystallography), the first of its kind to be reported. Two of the corroles are characterized by cyclic voltammetry and spectroelectrochemistry in dichloromethane, and the site of electron transfer is elucidated.

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“…We explored this possibility and selected Ag II TPP (TPP = tetraphenylporphyrin) for the present study. Our expectation was based on the observations that the chemical [12,13] or electrochemical reduction [14,15] of silver(II) porphyrins is associated with a demetalation. It occurs because in distinction to the smaller Ag 2+ ion, Ag + is too large for the hole in the N 4 frame.…”

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confidence: 99%