Chiral induced spin selectivity in achiral poly(amino acid)s acting as transducers of centrochiral information via the sergeant and soldier effect

Abstract

Chiral materials can induce spin selectivity (CISS) in electron transport, creating spin-polarization without the need of external magnetic fields. This effect has received attention in chiral soft matter, where symmetries like centro-, axial and helical chirality are accessible by molecular design and transform into the specific spin polarization of electrons in interaction with solid matter. We here have designed helices as achiral transducers of chirality to transmit a CISS effect over ~ 6 nm, linked to a centrochiral molecule distant to the surface solely via an induced helical chirality. Based on a 310-helix built from the achiral amino acid, α-aminoisobutyric acid (Aib), dynamic helices are generated in their oligomeric forms A*-(Aib)n–S (n = 7−15, A*: chiral head group; S: sulfur)), enhanced by the chirality of only one centrochiral molecule (A*) attached as head group. When adsorbed on a gold surface a selfassembled monolayer of 4 ~ 6 nm height is formed, further probing the CISS effect of the respective Rand S-forms and the induced left-handed M- or right-handed P-helices. By conductive atomic force microscopy (c-AFM) and scanning tunneling microscopy (STM) measurements, we demonstrate that it is possible to transfer the effect of chirality of a centrochiralmolecule via an achiral transmitting-block to induce CISS effects of high efficiency, now spatially separated from the source of chirality. The electron-transporting abilities and the unique folding into a 310-helix are hold responsible to reach the here observed high spin polarization (up to 99%by c-AFM, up to 90%by STM), which is among the highest reported for peptide-based molecules.