Communication: The high substituent sensitivity of the electrical conductivity of copper DCNQI radical anion salts (see figure) is attributed to the fact that the stacks of copper atoms and bridging DCNQI ligands are convalently clamped together within the framework of a sevenfold interpenetrating super-diamond architecture. This observation should influence more quantitative approaches to explaining and modeling the conductivity behavior of the Cu(DCNQI)2 salts.