Switchable circular dichroism and ionic migration dominated charge transport in a chiral spin crossover polymer

We demonstrate thermally switchable chiroptical activity in a chiral spin crossover (SCO) material, where circular dichroism is significant in the low spin state but quenched in the high-spin state for both enantiomers. With magnetometry we establish a cooperative transition with hysteresis near room temperature. Fe L3,2 edge Xray absorption directly links the quenching of chirality to a reorganization of Fe 3d electronic structure that accompanies the spin state transition. Moreover, electrical measurements show pronounced I(V) hysteresis and cycling dependent C(V) behavior, indicating transport in this chiral SCO material is dominated by ionic migration rather than mobile electrons or holes.