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.

Chiral Induced Spin Selectivity

“…More recently, CISS studies at the single molecule level have been performed by Burgler and co-workers, who used spinpolarized STM to examine the enantioselective adsorption of chiral molecules on magnetic surfaces, 47,48 and by Ortunõ 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%. 49 Collectively, these experiments demonstrate that CISS manifests at the single molecule level.…”

Role of Electrode Polarization in the Electron Transport Chirality-Induced Spin-Selectivity Effect

“…To date, elucidating the origin of the CISS effect is considered to be an outstanding open problem. , While many different theoretical proposals for the origin of CISS were put forward, there is an active ongoing debate, and a clear picture is yet to emerge. One can divide the suggested mechanisms pertaining to the transport-manifestation of the CISS effect into two main groups, namely theories based on spin–orbit coupling (SOC) in noninteracting electrons (e.g. − ), and theories based on some form of interaction; magnetic, , electron–phonon, − Coulomb interactions, , and more. − …”

Mechanical Manipulation of Quantum Interference in Single‐Molecule Junctions

“…Mechanical manipulation of the molecular junction as a way of changing its charge transport efficiency is an enticing alternative. [17] Through mechanosensitive phenomena (dependence of charge transport efficiency on applied force or mechanical displacement) a fine level of control on junction conductance has been achieved, for instance, by exploiting interfacial effects at the pyridyl, [18,19] thienyl [20] or carbodithioate [21] electrode contact or in carotenoid molecular wires, [22] by using molecules with multiple metallophilic groups spaced along the conductive backbone, [23][24][25][26] or by employing flexible molecules that can fold/unfold (synthetic foldamers), [27][28][29] rotate, [30] or shear [31,32] along an axis. Of all these methods, only the use of flexible molecules provides real mechanical manipulation of the transport orbitals.…”