Insights into the free-energy dependence of intramolecular dissociative electron transfer

To study the relationship between rate and driving force of intramolecular dissociative electron transfer, a series of donor-spacer-acceptor systems (D-Sp-A) has been devised and synthesized. Cis-1-aminocyclohexane-4-carboxylic acid and a perester functional group were kept constant as the spacer and the acceptor, respectively, whereas unsubstituted or variously substituted phthalimide groups were selected as the donors. X-ray crystallography and ab inition conformational calculations pointed to D-Sp-A molecules having the cis-(cyclohexane) equatorial(phthalimido) - axial(perester) conformation and the same D/A orientation. The electrochemical analysis provided clear evidence of a concerted dissociative electron-trasfer mechanism. The intramolecular rate constants were determined and compared with the corresponding intermolecular values, the latter being obtained by using model molecules.