  Spin-crossover (SCO) molecules are versatile magnetic switches with
applications in molecular electronics and spintronics. Downscaling devices to
the single-molecule level remains, however, a challenging task since the
switching mechanism in bulk is mediated by cooperative intermolecular
interactions. Here, we report on electron transport through individual Fe-SCO
molecules coupled to few-layer graphene electrodes \textit{via} $\pi - \pi$
stacking. We observe a distinct bistability in the conductance of the molecule
and a careful comparison with density functional theory (DFT) calculations
allows to associate the bistability with a SCO-induced orbital reconfiguration
of the molecule. We find long spin-state lifetimes that are caused by the
specific coordination of the magnetic core and the absence of intermolecular
interactions according to our calculations. In contrast with bulk samples, the
SCO transition is not triggered by temperature but induced by small
perturbations in the molecule at any temperature. We propose plausible
mechanisms that could trigger the SCO at the single-molecule level.
