Transport properties of binuclear metal complexes of the VIII group using a simplified NEGF-DFT approach

Abstract

We report on a theoretical study of the electronic transport properties of binuclear complexes of metals of the VIII group bridged by pyrazine. Metal–porphyrazine units have been combined in order to investigate symmetric and non-symmetric species with particular focus on their current rectification properties. Transmission functions and I–V characteristics of the various species have been computed using a Non-Equilibrium Green Function with a simplified treatment of the molecule–lead interaction. The results obtained show an overall moderate asymmetry in the current along the molecules, which is of the donor–σ–acceptor type and follow the trend of the ionization potential of the metals in the binuclear system. The bias-dependent rectification ratio, which is significant in a limited voltage window, can be explained in terms of the alignment of the occupied orbitals of the metallic fragments that contribute to the HOMO and HOMO − 1 of the supermolecule. The possible improvement of the rectification performance of such a class of molecules has also been investigated exploiting suitable substitution by electron-withdrawing groups.