Spin Filtering in Supramolecular Polymers Assembled from Achiral Monomers Mediated by Chiral Solvents.

Amit Kumar Mondal,Ghislaine Vantomme,Ron Naaman,Tapan Kumar Das,E W Meijer,Marco D Preuss,Marcin L Ślęczkowski

doi:10.1021/jacs.1c02983

Abstract

In past studies, spin selective transport was observed in polymers and supramolecular structures that are based on homochiral building blocks possessing stereocenters. Here we address the question to what extent chiral building blocks are required for observing the chiral induced spin selectivity (CISS) effect. We demonstrate the CISS effect in supramolecular polymers exclusively containing achiral monomers, where the supramolecular chirality was induced by chiral solvents that were removed from the fibers before measuring. Spin-selective transport was observed for electrons transmitted perpendicular to the fibers’ long axis. The spin polarization correlates with the intensity of the CD spectra of the polymers, indicating that the effect is nonlocal. It is found that the spin polarization increases with the samples’ thickness and the thickness dependence is the result of at least two mechanisms: the first is the CISS effect, and the second reduces the spin polarization due to scattering. Temperature dependence studies provide the first support for theoretical work that suggested that phonons may contribute to the spin polarization.

Highlights

In recent years, it was established that electron transport through homochiral molecules depends on the electron spin
The materials are based on chiral building blocks with specific configurations at the stereocenters and exciting results were obtained with chiral supramolecular polymers
Next to chiral monomers, supramolecularchirality has been induced by other external stimuli such as mechanical stress,[16−21] illumination with circularly polarized light,[22−25] or chiral solvents.[12,26−28] In cooperative systems,[29] through which small energy differences accumulate into large effects, minor differences in solvation energy between P and M helical aggregates in chiral solvents can drive the supramolecular aggregate of achiral monomers to favor one helicity over the other.[27]

Summary

Introduction

It was established that electron transport through homochiral molecules depends on the electron spin. This phenomenon, named Chiral Induced Spin Selectivity (CISS) effect, means that chiral molecules can serve as efficient spin filters.[1] During the past years, the CISS effect has been explored in biomolecules like DNA,[2] oligopeptides,[3] proteins,[4] polymers,[5] as well as in chiral perovskites,[6−8] chiral supramolecular structures,[9] and other molecules. These recent findings allow discovering whether spin selection can be obtained solely due to chiral stacking of otherwise achiral building blocks

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Results

Conclusion