Redox-dependent self-sorting toggles a rotary nanoswitch.

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.