Effect of spin state and junction configuration in the conductivity of metal-bisdicarbollide cages

A computational study of the effect of magnetic state and junction geometry in the conductive properties of metal-bisdicarbollide-containing molecules is presented here. Two carborane cages, with a metal atom (Fe or Co) in the middle are connected to electrodes via a sulfur-terminated thiophene ring at each side. In the first study where the metal atom is Fe, a strong dependence of the conductivity on the spin state is observed showing the potential application of this molecule for storage or switching. In the second part of the study, with Co as the central atom, it is shown that at low voltage, as a tip-shaped electrode is pulled away, conductivity increases rather than decreasing. The phenomenon is attributed to the destabilization of the HOMO-2 (first conductive orbital) that moves up in energy towards the Fermi level leading to a lower onset for conduction.