  The oxidation and spin state of a metal-organic molecule determine its
chemical reactivity and magnetic properties. Here, we demonstrate the
reversible control of the oxidation and spin state in a single Fe-porphyrin
molecule in the force field of the tip of a scanning tunneling microscope.
Within the regimes of half-integer and integer spin state, we can further track
the evolution of the magnetocrystalline anisotropy. Our experimental results
are corroborated by density functional theory and wave function theory. This
combined analysis allows us to draw a complete picture of the molecular states
over a large range of intramolecular deformations.
