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

TL;DR

This study reveals a thermally switchable chiroptical activity in a chiral spin crossover material, where charge transport is dominated by ionic migration and is linked to spin state transitions.

Contribution

It demonstrates the first direct link between spin state, chiroptical activity, and ionic migration in a chiral SCO polymer.

Findings

Chiroptical activity is significant in low spin state and quenched in high spin state.

Electrical measurements show ionic migration dominates charge transport.

Hysteresis observed in both magnetic and electrical properties.

Abstract

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.