Marcus solvent broadening

The rate constants and activation parameters (including AV ) for electron self-exchange in the [Mn(CNC(CH)3)6]-"/ -" and [Mn(CNC6Hu)6] couples have been determined by Mn NMR line broadening in several pure and binary organic solvent systems. The values of A V cover a range of about 12 cm moP (-9 to -21 cm mol ) with no simple correlation with solvent parameters observed. A self-exchange rate constant of 0.7 0.4 M" s" has been calculated for the [Mn(edta)(H20)] and [Mn(cdta)(H20)] couples from the application of the Marcus relationship to outer-sphere cross-reactions with a variety of metal complexes in aqueous solution. Deviations from the correlation were observed for the nonadiabatic reactions with osmium tris(polypyridine) complexes. 

Line broadening in nmr experiments has been used to determine self-exchange rates for [Ru(4,4 -Me2bipy)(hfac)2] , [Ru(4,4 -Me2bipy)-(acac)2] and [Ru(hfac)3] in acetonitrite solution. The reactions are outer-sphere in nature and vary with solvent dielectric according to Marcus expectations. 

The rate constants and activation parameters for the electron selfexchange reactions of the [CrCCNdipp) ] and [Cr(CNdipp)g] (CNdipp = 2,6-diisopropylphenyl isocyanide) couples have been determined by H NMR line-broadening as a function of solvent. The rate constants show little variation with the nature of the nonaqueous solvent and agree well with predictions of the Marcus model. The variation in the activation parameters with solvent, displaying an enthalpy/entropy compensation, is not well predicted by the Marcus model. Added BF has little effect on the rate constants and activation parameters (AV = +2 to +11 cm mol ) for the... 

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