Magnetic field effects on the [bis[3-[(5-nitrosalicylidene)amino]propyl]methylaminato]manganese-catalyzed oxidation of 2,6-di-tert-butyphenol: hydrogen-2 and oxygen-17 magnetic isotope effects

Magnetic field effects in rates of reactions between radicals and transition metal coordination complexes of cobalt(II) and manganese(II): probes for spin polarization

“…The magnetokinetic behavior of the Co(II) reactions considered above is in contrast with a monotonic dependence of the rate constant for the disappearance of the C03H radical on B (Figure 2a) and for the C03H reactions, eqs 9 and 10, with Mn(OH2)e2+ and with Mn(EDTAH)-(Figure 2b,c). In the flash photochemical Mn(OH2)62+ + C03H -Mn(0H2)50C02H2+ (9) Mn(EDTAH)" + C03H -Mn(EDTAH)0C02H" (10) study of these reactions, the decay of the radical C03H was followed at 620 nm. Rates for the scavenging processes, eqs 9 and 10, were determined with concentrations of the Mn(II) complexes, [Mn(OH2)62+] > 7.0 X lCHMand [Mn(EDTAH)-] > 4.0 X 10-3 M, equal to or higher than those making their lifetimes 1 -order of magnitude shorter than the lifetime of C03H.…”

Spin-orbit coupling in free-radical reactions: on the way to heavy elements

“…It is worthwhile to mention in this section the MFE study in the dark oxidation reactions of 2,6-dialkylphenols into p-quinones and diphenoquinones catalyzed by Co(II) (S = 3/2; V2) and Mn(II) (S = 5/2). [187][188][189] The singlet RP, which has a metal-centered radical is formed in a magnetosensitive step. The analysis of field dependences in the spirit of ref 180 (see above) enables one to estimate relative contributions of SOC and HFC to S-T evolution of the RP under investigation.…”

On the Adiabaticity Contribution to the Rate of Outer-Sphere Electron Transfers. Reactions of Cytochrome c and Related Transition Metal Compounds

“…The assumption that anisotropies in the g tensor (Zeeman mechanism) and A tensor (contact interaction) are averaged by fast random displacements of one reactant relative to the other was applied to . This approximation has been previously used in reactions between inorganic radicals, radicals with coordination compounds, and outer-sphere electron transfers when B < 2 T. ,− The rotation and internal vibrations, i.e., metal−ligand and ligand−skeletal, of one reactant referenced to the coordinates of the other can be used as time-dependent perturbations V ( t ) 3b. In times shorter than the autocorrelation time, the anisotropic components of g and A in the Hamiltonian and these V ( t ) perturbations provide a “relaxation mechanism” for the conversion among spin states 3b.…”

“…(a) Radical Pair Mechanisms . The radical pair, RP, or the radical ion pair, RIP, mechanisms provide a solid theoretical framework for the rationalization of such effects in some particular redox reactions involving radicals. ,− In these mechanisms, radical pairs or radical ion pairs are stochastically joined in a given spin state. The rate of the dynamic evolution from the stochastically formed spin state to other available spin states is affected by the magnetic field.…”

“…Pairs in states uncorrelated with the states of the products are separated before they react; i.e., their constituents are returned to the bulk. Literature examples have shown that these mechanisms successfully account for the observed magnetokinetic effect (MKE) in a variety of reactions between inorganic radicals and reactions between inorganic radicals and transition metal compounds. 3c,d,− Aside from these successes, these mechanisms do not explain the MKE in many outer-sphere electron-transfer reactions, at least in those reactions between transition metal compounds.…”