Chiral Single‐Molecule Potentiometers Based on Stapled ortho‐ Oligo(phenylene)ethynylenes

Abstract

We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau-length distributions, attributed to different conformations of the helical structures. The large chiro-optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state-of-theart Density Functional Theory (DFT) calculations, including a fully ab-initio estimation of the CISSoriginating spin polarization which is done, for the first time, for a realistic molecular system.

Interrogating the CISS effect in chiral and paramagnetic organic radicals: the impact of the molecular spin over the total spin polarization

“…The latter was calculated as: P = T↑↑ + T↑↓ − T↓↓ − T↓↑where each term corresponds to the transmission calculated for all possible combinations of initial and final directions of the travelling spin for a given choice of the quantization axis (the transport direction here). SOC is only significant for Au atoms but, as shown in previous works, 95–97 it gives rise to spin polarization. This is particularly so below the Fermi level, but also at the Fermi level if a molecular orbital lies in the vicinity, which is the case here; both curves show a peak positioned at the Fermi level, originating from the presence of the radical, due to the alignment of its SOMO (single occupied molecular orbital) level with the E F .…”

“…Theoretical calculations based on the nonequilibrium Green's functions (NEGF) approach, as successfully done previously for other systems, 95–97 (Section S8 in the ESI†) were carried out to shed light on the lack of CISS effect observation. With this aim, a junction comprising bPTM between two gold clusters was considered, as shown in Fig.…”

Chirality-Induced Spin Selectivity in Supramolecular Chirally Functionalized Graphene

“…Consequently, achiral fibers with null CD resulted in no spin selection. Although a correlation between the CISS effect and the sign and magnitude of the CD of the conductive material has been suggested in earlier reports, − the present result shows that the CD signal of the chiral inductor could also infer the CISS response of the composite material.…”

Chiral Induced Spin Selectivity

“…Note that these measurements did not display a perfect antisymmetry, and it was necessary to invoke a spin-to-charge voltage (or “spinterface” effect, see Section ) to fully explain the data. More recently, CISS studies at the single molecule level have been performed by Bürgler and co-workers, who used spin-polarized STM to examine the enantioselective adsorption of chiral molecules on magnetic surfaces, , and by Ortuño et al, who have developed a chiral oligo­(phenylene)­ethynylene based molecular tunnel junction and used theoretical calculations to predict spin polarizations of 20% to 40% . Collectively, these experiments demonstrate that CISS manifests at the single molecule level.…”