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.
Mamontov et al. (Tue,) studied this question.