Calculated electron affinities and redox E° values of polypyridinic derivatives

Quantum mechanical based ab-initio calculations are used to compute one-electron electrochemical standard reduction potentials, E-0, for a set of 12 polypyridinic derivatives (plus nitrobenzene and benzophenone as reference compounds) in dimethylformamide solution. Linear relationships between theoretical predictions and experimental data are constructed and provide a mean unsigned error of about 0.19 V. It is shown that the theoretical approach allows us also to discuss structural features related to the electron transfer process, like conformational changes found between the neutral and radical anion species (for instance, in the case of 4-4´dipyridyl a variation is found from 36degrees to almost zero of the ring-ring dihedral angle and a shortening of the single C-C bond when passing from the neutral to the radical anion). Also the weight of different terms (mainly: electron affinity, solvation Gibbs energies, DeltaG(0) of the 1/2 H-2(g), H-aq(+) + e(-) half-cell reaction) leading to the determination of E-0 is assessed on a quantitative basis.