  We analyze the electronic transport through a model spin-1 molecule as a
function of temperature, magnetic field and bias voltage. We consider the
effect of magnetic anisotropy, which can be generated experimentally by
stretching the molecule. In the experimentally relevant regime the conductance
of the unstretched molecule reaches the unitary limit of the underscreened
spin- 1 Kondo effect at low temperatures. The magnetic anisotropy generates an
antiferromagnetic coupling between the remaining spin 1/2 and a singular
density of quasiparticles, producing a second Kondo effect and a reduced
conductance. The results explain recent measurements in spin-1 molecules
[Science 328 1370 (2010)].
