  We demonstrate that the critical temperature for valence tautomeric
interconversion in Cobalt dioxolene complexes can be significantly changed when
a static electric field is applied to the molecule. This is achieved by
effectively manipulating the redox potential of the metallic acceptor forming
the molecule. Importantly our accurate density functional theory calculations
demonstrate that already a field of 0.1 V/nm, achievable in Stark spectroscopy
experiments, can produce a change in the critical temperature for the
interconversion of 20 K. Our results indicate a new way for switching on and
off the magnetism in a magnetic molecule. This offers the unique chance of
controlling magnetism at the atomic scale by electrical means.
