The pyridine–pyrimidine (py–pym) arm as the moving part of the two-state nanomechanical rotary switch [Cu(1)]⁺ is toggled reversibly between two stations using one-electron oxidation/reduction. In state I, the arm is attached via Cu⁺ complexation to a sterically encumbered phenanthroline and in state II to a zinc porphyrin station. Toggling is realised by charging and discharging an external input signal, the ferrocene-appended diimine ligand 2. Addition of 2 leads to formation of the intermolecular complex [Cu(1)(2)]⁺ paralleled by a move of the py–pym arm to the zinc porphyrin station. Upon oxidation at the ferrocenyl unit, 2⁺ detaches from [Cu(1)(2)]²⁺ so that [Cu(1)]⁺ is formed in state I. Switching was ascertained by NMR, UV-Vis spectroscopy and cyclic voltammetry.