Chirality-Induced Spin Selectivity in an Achiral Electron Donor–Acceptor Molecule Doped into a Cholesteric Liquid Crystal

Chirality-induced spin selectivity (CISS) enables control over radical pair spin dynamics for applications in quantum information science (QIS). In this study, we show that this control can be achieved through supramolecular chirality transfer, rather than relying on the intrinsic molecular chirality of the molecule used to generate the radical pair. We investigate how doping an achiral donor-bridge-acceptor (D-B-A) molecule into a cholesteric liquid crystal affects the spin dynamics of a spin-correlated radical pair (D^•+-B-A^•-, SCRP) formed by photoinitiated, subnanosecond, two-step charge separation, where D = <i>p</i>-methoxyaniline (MeOAn), B = 4-(<i>N</i>-piperidinyl)naphthalene-1,8-dicarboximide (ANI), and A = naphthalene-1,8:4,5-bis(dicarboximide) (NDI), compound <b>1</b>. The cholesteric phase of 4-cyano-4'-<i>n</i>-pentylbiphenyl (5CB) was prepared by the addition of the chiral dopant (<i>R</i>)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate (R811) or its enantiomer (S811). Compound <b>1</b> was then doped into these mixtures to form (<b>1</b>/5CB/R811) and (<b>1</b>/5CB/S811). Circular dichroism spectra indicate that chirality transfer occurs from the chiral medium to <b>1</b>. Time-resolved electron paramagnetic resonance spectroscopy at 85 K was used to observe the SCRP resulting from photoexcitation of B in <b>1</b> aligned in 5CB/R811 and 5CB/S811, as well as in 5CB lacking the chiral dopant. The resulting spectra reveal distinct line shape changes indicative of a strong CISS contribution (>83%) to the spin dynamics of D^•+-B-A^•- formation in the cholesteric phase of 5CB/R811 and 5CB/S811. These results demonstrate that CISS can be effectively induced by supramolecular chirality transfer in SCRPs that lack intrinsic molecular chirality; thus expanding the potential use of CISS for QIS applications.