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Kinetic and Mechanistic Studies on the Oxidation of Nitrogen(III) (HNO 2 / $\rm{{{NO}}_2^ - }$ ) by the Tris(biguanide)manganese(IV) Ion in Aqueous Acidic Media
Author(s) -
Das Amit,
Mukhopadhyay Subrata
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590195
Subject(s) - chemistry , protonation , aqueous solution , electron transfer , manganese , inorganic chemistry , ligand (biochemistry) , oxidizing agent , nitrite , redox , stoichiometry , proton coupled electron transfer , kinetics , reaction rate constant , aquation , ion , medicinal chemistry , photochemistry , nitrate , organic chemistry , biochemistry , physics , receptor , quantum mechanics
The kinetics of a net two‐electron transfer between an authentic Mn IV complex, [Mn(bigH) 3 ] 4+ ( Fig. 1 ; bigH = biguanide = C 2 N 5 H 7 ), and nitrite in aqueous solution in the pH interval 2.00–3.60 is described. Stoichiometric data for the reaction clearly indicates Δ[Mn IV ]/Δ[N III ] T = 1.07 ± 0.10, and $\rm{{{NO}}_3^ - }$ is detected as the oxidized product of nitrite ([N III ] T = [HNO 2 ] + [ $\rm{{{NO}}_2^ - }$ ]). Though both HNO 2 and $\rm{{{NO}}_2^ - }$ are found to be reactive, the latter is kinetically superior in reducing the fully protonated Mn IV complex. Proton‐coupled electron transfer (PCET; 1e, 1H + ) reduces the activation barrier for the thermodynamically unfavorable reaction of weakly oxidizing Mn IV species. At the end of the redox process, the ligand bigH is released, and the high protonation constants of the ligand carry the overall reaction to completion.