Close-Shell and Biradical Enantiomers for Probing the Chiral-Induced Spin Selectivity Effect

Two pairs of enantiomers were designed, synthesized, and characterized. They differ by the absence or presence of two unpaired electrons, enabling us to probe the role that close- versus open-shell electronic structures play on chiroptical properties and the chiral-induced spin selectivity (CISS) effect. The enantiomers showed comparable high purity and an enantiomeric excess of >99%, enabling accurate physical studies. Specifically, circular dichroism in solution and gold-coated thin films and the chiral-induced anomalous Hall effect were measured and discussed in the light of the molecular structure. The biradical enantiomers showed a magnified CISS effect in spectroscopic and electric measurements versus that of the close-shell enantiomers.