Naphthalenes Oxidation by Aqueous Sodium Hypochlorite Catalyzed by Ruthenium Salts Under Phase-Transfer Catalytic Conditions

Spectroscopic characterization of a Ru(III)-OCl intermediate: a structural mimic of haloperoxidase enzymes

Haloperoxidase enzymes utilize metal hypohalite species to halogenate aliphatic and aromatic C-H bonds to C-X (X = Cl, Br, I) in nature. In this work, we report the synthesis and spectroscopic characterization of a unique Ru^III-OCl species as a structural mimic of haloperoxidase enzymes. The reaction of [(BnTPEN)Ru^II(NCCH₃)]²⁺ (BnTPEN = N¹-benzyl-N¹,N²,N²-tris(pyridine-2-ylmethyl)ethane-1,2-diamine) with hypochlorite in the presence of an acid in CH₃CN : H₂O mixtures generated a novel [(BnTPEN)Ru^III-OCl]²⁺ species that persists for 4.5 h at room temperature. This new species was characterized by UV-vis absorption, EPR, and resonance Raman spectroscopic techniques, and ESI-MS. The Ru^III-OCl species is capable of performing oxygen atom transfer and hydrogen atom abstraction to various organic substrates.

A Kinetic Study on the Efficient Formation of High-Valent Mn(TPPS)-oxo Complexes by Various Oxidants

New, more efficient methods of wastewater treatment, which will limit the harmful effects of textile dyes on the natural environment, are still being sought. Significant research work suggests that catalysts based on transition metal complexes can be used in efficient and environmentally friendly processes. In this context, a number of compounds containing manganese have been investigated. A suitable catalyst should have the capacity to activate a selected oxidant or group of oxidants, in order to be used in industrial oxidation reactions. In the present study we investigated the ability of MnIII(TPPS), where TPPS = 5,10,15,20-tetrakis(4-sulphonatophenyl)-21H,23H-porphyrine, to activate five different oxidants, namely hydrogen peroxide, peracetic acid, sodium hypochlorite, potassium peroxomonosulfate and sodium perborate, via the formation of high valent Mn(TPPS)-oxo complexes. Kinetic and spectroscopic data showed that the oxidation process is highly pH dependent and is strongly accelerated by the presence of carbonate in the reaction mixture for three of the five oxidizing agents. The highest efficiency for the oxidation of MnIII(TPPS) to high-valent Mn(TPPS)-oxo complexes, was found for peracetic acid at pH ≈ 11 in 0.5 M carbonate solution, which is at least an order of magnitude higher than the rate constants found for the other tested oxidants under similar conditions.