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Titolo:
Kinetic studies on the interactions of manganese-porphyrins with peraceticacid. Part 2. The influence of acetic acid and porphyrin substituents
Autore:
Banfi, S; Cavazzini, M; Pozzi, G; Barkanova, SV; Kaliya, OL;
Indirizzi:
CNR, Dipartimento Chim Organ & Ind, I-20135 Milan, Italy CNR Milan ItalyI-20135 artimento Chim Organ & Ind, I-20135 Milan, Italy CNR, Ctr Studio Sintesi & Stereochim Speciali Sistemi, I-20135 Milan, Italy CNR Milan Italy I-20135 tereochim Speciali Sistemi, I-20135 Milan, Italy Organ Intermediates & Dyes Inst, Moscow, Russia Organ Intermediates & DyesInst Moscow Russia Dyes Inst, Moscow, Russia
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
, volume: 4, anno: 2000,
pagine: 879 - 885
SICI:
0300-9580(2000)4:<879:KSOTIO>2.0.ZU;2-B
Fonte:
ISI
Lingua:
ENG
Soggetto:
AXIAL LIGAND; BIOMIMETIC OXIDATION; ALKENE EPOXIDATIONS; 2-PHASE CONDITIONS; AQUEOUS-SOLUTION; CATALYSTS; AGGREGATION; MECHANISM; COMPLEXES; WATER;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
30
Recensione:
Indirizzi per estratti:
Indirizzo: Banfi, S Univ Insubria, Dipartimento Biol Strutturale & Funz, Via Dunant 3, I-21100Varese, Italy Univ Insubria Via Dunant 3 Varese Italy I-21100 100Varese, Italy
Citazione:
S. Banfi et al., "Kinetic studies on the interactions of manganese-porphyrins with peraceticacid. Part 2. The influence of acetic acid and porphyrin substituents", J CHEM S P2, 4, 2000, pp. 879-885

Abstract

The one-electron oxidation of 1,1-diphenyl-2-picrylhydrazine (DPPH) and Zn-tetra-tert-butylphthalocyanine (PcZn) to the corresponding stable radical (DPP.) and pi-radical cation (PcZn+.) with peracetic acid in acetonitrile-acetic acid has been studied, in the presence of Mn-III complexes of meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RTDCPPMnCl; R=CH3O, H, Br, Cl or NO2) as catalysts. The formation of a two-centre donor-acceptor complex of "catalyst-oxidant" type (adduct 'A') with rate constant k(1) is the first stage of the reaction. The balance of the electron donating properties of the porphyrin ring and electron accepting properties of Mn-III determines the formation of 'A', as shown by the independence of k(1) of catalyst structure. The influence of added acetic acid on the UV-Vis spectra of RTDCPPMnX in CH3CN and on the oxidation rate of DPPH and PcZn evidenced that a molecule of AcOH is included in the internal co-ordination sphere of RTDCPPMnX and of the reaction intermediates. The rate constant k(2) for the irreversible transformation of 'A' into an equilibrium mixture of Mn-V and Mn-IV oxo-species (established in Part 1) must thus refer to the acetic acid adducts of Mn-porphyrins {[RTDCPPMn(AcOH)](X)}. A non-linear dependence of log k(2)(rel) on sigma(para) of the porphyrin substituents R has also been found. However, electron-withdrawing substituents are particularly effective for enhancement of the rate of formation of the high-valent oxomanganese species.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 01/12/20 alle ore 07:55:11