Stereoselectivity in Charge and Spin Transport: From Open-Shell Nonconjugated Monomers to Polymers

Traditional spintronic materials that employ non-magnetic metals face challenges in maintaining spin polarization, which results in short spin relaxation times (~10 ns) due to their strong spin-orbit couplings. Nonconjugated open-shell polymers are promising spinterface material candidates due to their enhanced relaxation time (i.e., 10 µs) and paramagnetic nature, in contrast to closed-shell counterparts. Above all, the flexibility of the synthetic approach enables a deeper understanding of the fundamental physics behind spin-polarized transport, particularly in derivatives like stereo-controlled chemical structures. Herein, we synthesized a stable oxo-verdazyl radical monomer and polymer using stereoselective techniques, resulting in atactic and meso-rich polymers. First, single crystals of monomers showed the highest reported conductivity in nonconjugated radical systems, with decent magnetoresistance (MR) within a charge transport model. Furthermore, spin valves demonstrated increasing MR as meso-enrichment occurred, providing insights into spin transport based on structure. Lastly, spin-pumping devices were conducted and performed an opposite sign of output voltage on its isotactic conformation, as a first demonstration of tacticity control compassing inverse-spin hall effect in organic based spintronic systems. This work offers the first glimpse at stereoregularity for controlling spintronics-related electronic and magnetic properties in radical polymers.