Chiral Recognition and Stereoselective Reduction of Horse Ferricytochrome c by Optically Active Iron(ll) Complexes

The reduction of ferricytochrome c with the chiral complexes [Fe(alamp)] (alamp = N,N'-[(pyridine-2,6-diyl)bis(methylene)]bis[(R)- or (S)-alanine]) and [Fe(promp)] (promp = N,N'-[(pyridine-2,6-diyl)bis(methylene)]bis[(R)- or (S)-proline] is moderately stereoselective. The temperature dependence of the stereoselectivity shows ΔΔH#Δ-Λ/ΔΔS#Δ-Λ compensation behaviour giving crossing Eyring plots at 28° and 36° for alamp and promp, respectively. The activation parameters of the two ligands show inverted signs indicating that electron transfer with the corresponding Fell complexes probably does not occur in an identical geometrical environment.