Article: article from journal or magazin.
Stereoselectivity in the reaction of spinach plastocyanin with optically-active reducing agents
Journal of the Chemical Society, Chemical Communications
The kinetics of the reduction of spinach plastocyanin by optically active iron(II) complexes of 2,6-bis[3-(S)- or 3-(R)-carboxy-2-azabutyl]pyridine [(S,S)- or (R,R)-ALAMP] have been studied and the complex with (R,R)-ALAMP (Δ-configuration) reacts 1.6 to 2.0 times faster at different values of pH and temperature than the (S,S)-enantiomer; the activation parameters show that this observed stereoselectivity is a consequence of the differences in the activation entropies (ΔΔS?(Δ-Λ)=+15 J mol-1 K-1), which over-compensates the effect of the activation enthalpy, the latter being in favour of the complex with the Δ-configuration (ΔΔH?(Δ-Λ)=+ 3.0 kJ mol-1).
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