A Dinuclear Cobalt Complex Featuring Unprecedented Anodic and Cathodic Redox Switches for Single-Molecule Magnet Activity

One-electron
oxidation or reduction of the paramagnetic dinuclear
Co­(II) complex dmp2Nin­{Co­[N­(SiMe3)2]}2 (1; dmp2Nin2– = bis­(2,6-dimethylphenyl)­nindigo), by fully reversible chemical
or electrochemical methods, generates the radical salts [1(OEt2)]+ and [1]−, respectively. Full structural and magnetic analyses reveal the
locus of the redox changes to be nindigo-based, thus giving rise to
ligand-centered radicals sandwiched between two paramagnetic and low-coordinate
Co­(II) centers. The presence of these sandwiched radicals mediates
magnetic coupling between the high-spin (S = 3/2) cobalt ions, which gives rise to single-molecule
magnet (SMM) activity in both the oxidized ([1(OEt2)]+) and reduced ([1]−) states. This feature represents the first example of a SMM exhibiting
fully reversible, dual “ON/OFF” switchability in both
the cathodic and anodic states.