Mechanistic aspects of outer-sphere reduction of CoIII(en)2(Br)(L)2+ (L = RC6H4NH2) complexes in binary solvent mixtures: A critical and quantitative assessment of linear free energy relations

Reduction between View the MathML sourceFe(CN)64-–CoIII(en)2(Br)(L)2+ (where L = RC6H4NH2 and R = m -OMe, p -F, H, m -Me, p -Me, p -OEt and p -OMe) was investigated as a function of solvent composition (0%, 5%, 10%, 15%, 20%, 25% and 30% (v/v) of methanol or 1,4-dioxane in water) at 287, 293 and 300 K and 0.3 M NaClO4. As auxiliary data, the rate constant of reduction (k 2) is dependent on the mole fraction (x 2) of organic co-solvent and medium relative permittivity, consistent with the involvement of long range and short range solvent interactions on View the MathML sourceCoIII(en)2(Br)(L)2++Fe(CN)64-↔{CoIII(en)2(Br)(L)2+;Fe(CN)64-}→products. Rigorous unified and multiple statistical model equations of the form View the MathML source(YS=Y0+∑i=1naiXi) have been tested to explain the observed medium effects, which can establish an understanding of the fundamental factors influencing the solvent dependence of the reduction behavior of the complexes.