# A Density Functional Theory Based Electron Transport Study of Coherent Tunneling Through Cyclic Molecules Containing Ru and Os as Redox Active Centers

## TL;DR

This study uses DFT combined with NEGF to analyze electron transport in cyclic molecules with Ru and Os centers, finding no destructive quantum interference near the Fermi level and exploring structural influences on conductance.

## Contribution

It introduces a combined DFT and NEGF approach to investigate electron transport in Ru and Os containing molecules, clarifying structural factors affecting quantum interference.

## Key findings

- No destructive quantum interference near Fermi level in studied molecules.
- Local charging alters conductance by about one order of magnitude.
- Structural differences explain the absence of DQI compared to ferrocene compounds.

## Abstract

In our theoretical study in which we combine a nonequilibrium Green's function (NEGF) approach with density functional theory (DFT) we investigate branched compounds containing Ru or Os metal complexes in two branches, which due to their identical or different metal centers are symmetric or asymmetric. In these compounds the metal atoms are connected to pyridyl anchor groups via acetylenic and phenyl spacer groups in a meta-connection. We find there is no destructive quantum interference (DQI) feature in the transmission function near the Fermi level for the investigated molecules regardless of their symmetry, neither in their neutral states nor in their charged states. We map the structural characteristics of the range of molecules onto a simplified tight-binding model in order to identify the main differences between the molecules in this study and previously investigated ferrocene compounds in order to clarify the structural sources for DQI, which we found for the latter but not for the former. We also find that local charging on one of the branches only changes the conductance by about one order of magnitude which we explain in terms of the spatial distributions and charge-induced energy shifts of the relevant molecular orbitals for the branched compounds.