Electrochemical criteria are used to evaluate the electronic interaction between redox centres in the π-conjugated diyne complexes {RC=C[Co 2 (CO) 6 ]C=C[Co 2 (CO) 6 ]R} and {RC=C[Co 2 (CO) 6 ]-(S)-C=C[Co 2 (CO) 6 ]R} (R = Ph, Fc) where the aromatic spacer S is phenyl, napthalene or anthracene. Voltammetry at microelectrode, differential pulse techniques and low temperature measurements are used to obviate the chemical complications following the primary redox process. A mechanism is proposed which successfully simulates the electrochemical data.