Theoretical insights on the importance of anchoring vs molecular geometry in magnetic molecules acting as junctions

TL;DR

This paper investigates how anchoring points and molecular geometry perturbations influence the conductance and spintronic behavior of single-molecule junctions, highlighting the importance of molecular design over anchoring position for reproducibility.

Contribution

It provides a comparative analysis of anchoring versus molecular geometry effects on transport properties, revealing that anchoring position is less critical than molecular rigidity.

Findings

Small geometric alterations significantly affect conductance.

Changing anchoring points has limited impact on spintronic behavior.

Rigid molecular linkers are more crucial for reproducibility than anchoring position.

Abstract

The anchoring of the molecule to an electrode is known to be a key factor in single-molecule spintronics experiments. Likewise, a relaxation down to the most stable geometry is a critical step in theoretical simulations of transport through single-molecule junctions. Herein we present a set of calculations designed to analyze and compare the effect of different anchoring points and the effect of perturbations in the molecular geometry and interelectrode distance. As model system we chose the [V($\alpha$-C$_3$S$_5$)$_3$]$^{2-}$ complex connecting two Au(111) electrodes in a slightly compressed geometry. In our calculations, the attachment happens through an S-Au bond, a common anchoring strategy in molecular spintronics experiments. Our results confirm that small alterations in the molecular geometry have important effects in the conductance. We were able to compare these effects with the ones arising from changing the anchoring position with a constant molecular geometry. Unexpectedly, we demonstrate that the anchoring position has only a lesser relevance in the spintronic behavior of the device, as long as all other parameters are kept frozen. As a consequence, we predict that for experimentalists aiming for reproducibility, the molecular design of rigid linkers is more relevant than the design of univocal anchoring positions.