Effects of acceptor doping on a metalorganic switch: DFT vs. model analysis

Abstract

We propose a molecular switch based on copper dioxolene molecules with valence tautomeric properties. We study the system using density functional theory and a model Hamiltonian that can properly account for electronic correlations in these complex molecular systems. We compute the transport properties of the junction with a Cu–dioxolene unit sandwiched between gold electrodes and analyze its dependence on the valence tautomeric state of the molecule. We also study the effects of doping with ICl₂ acceptor molecules on the magnetic and electronic features of the device. We find that in the absence of dopants, the Cu–dioxolene unit is weakly charged in a S = 1/2 spin state. However, the acceptors increase the charge state of the molecule and make possible a transition between the high-spin (S = 1) triplet and the low-spin (S = 0) singlet. The I–V dependence shows a manifestation of spin filtering and a voltage-induced multistable behavior that can have several applications in nanoscale electronic devices.