An improved bond-order/bond-length relation for the calculation of inner sphere reorganization energies of organic electron transfer reactions

Abstract

It is shown that common bond-order/bond-length relations are not applicable to radical ions. A new relation for radical ions Q+!- is derived from experimental bond lengths. A Coulson type relation of the bond length qαϱ(Q+!-) between the atoms α and ϱ and the π-bond order Pxαϱ(Q+!-) is found to be: qαϱ(Q+-)/Å = 1.590-0.325. Pxαϱ(Q+!-). This relation permits to calculate the inner sphere reorganization energy λi, in the sense of Marcus’ theory for compounds where the crystallographic structure of the radical ion is not available.