AbstractNMR and Mössbauer spectroscopy show that a novel tetrathiol ligand, based on the cavitand diphenylglycoluril, encapsulates a 4Fe‐4S cluster and induces asymmetry in it. The cluster gives a weak electrochemical current response in DMF, with a half‐wave potential for the 2−/3−reduction vs. Fc+/Fc of ‐1.7 V. Ba2+ions are adsorbed, according to X‐ray analysis of the SEM image of the electrode, and act as modulator and promoter of the electrochemical response. On the basis of cyclic voltammograms it is proposed that this adsorption creates electroactive sites, changing the type of diffusion controlling the mass transport to the electrode from radial to linear, and that it helps the negatively charged complex, which contains a dipole, to approach the negative electrode in an orientation favourable for electron exchange. This feature makes the complex an important model for ferredoxins, in spite of a difference in red