  We investigate electron transport through a mixed-valence molecular complex
in which an excess electron can tunnel between hetero-valent transition metal
ions, each having a fixed localized spin. We show that in this class of
molecules the interplay of the spins and the vibrational breathing modes of the
ionic ligand-shells allows the total molecular spin to be detected as well as
controlled by nonequilibrium transport. Due to a spin-dependent pseudo
Jahn-Teller effect electronic transitions with different spin values can be
distinguished by their vibronic conductance side peaks, without using an
external magnetic field. Conversely, we show that the spin state of the entire
molecule can also be controlled via the nonequilibrium quantized molecular
vibrations due to a vibration-induced spin-blockade.
