Supramolecular Chiral Assembly of Open‐Shell Quinoids With Chiral Additives and Their Spin‐Dependent Transport in Magneto Field‐Effect Transistors

Why It Matters

The study proves that chiral organic assemblies can serve as efficient spin filters in transistor architectures, paving the way for low‑power, spin‑based electronics. It also offers a scalable method to harness intrinsic molecular spins alongside chirality, a key hurdle in organic spintronics.

Key Takeaways

• Open‑shell quinoids co‑crystallized with BN amplify chirality 30×.
• Thermal annealing yields stable chiral co‑crystals with g_abs 1.23e‑2.
• First magneto‑FETs using spin‑bearing chiral assemblies reported.
• Devices exhibit ~‑7.7% spin polarization via CISS effect.
• Asymmetric QF1 succeeds; symmetric QF2 shows phase separation.

Pulse Analysis

Chiral conjugated materials have surged to the forefront of organic electronics because they combine unique optical activity with the ability to filter electron spin, a phenomenon known as chirality‑induced spin selectivity (CISS). While many chiral polymers rely on external dopants to generate spin, intrinsic‑spin molecules remain scarce due to synthetic complexity and limited control over supramolecular order. The emergence of open‑shell quinoids—small molecules that host unpaired electrons—offers a promising platform, yet translating their spin properties into functional devices has been a persistent challenge.

In the new study, the team synthesized a series of fluorinated quinoids (QF1, QF2) and blended them with the chiral diamine BN. Hydrogen‑bonding between fluorine atoms and the amine’s N‑H groups drives a handedness transfer, but only the asymmetric QF1 forms a well‑mixed co‑crystal upon annealing. This thermal treatment locks the chiral arrangement, boosting the dissymmetry factor to 1.23 × 10⁻²—roughly thirty times higher than the unannealed mixture. By contrast, the symmetric QF2 segregates into separate phases, underscoring how subtle molecular symmetry dictates supramolecular chirality.

The breakthrough arrives when the QF1‑BN co‑crystals are integrated into magneto field‑effect transistors (m‑FETs). The devices exhibit a clear mirror‑image spin polarization of about –7.7% for opposite enantiomers, providing the first concrete evidence that chiral organic assemblies with intrinsic spins can directly modulate charge transport in a transistor geometry. This capability opens a pathway toward organic spintronic components that operate without magnetic electrodes, potentially reducing power consumption and enabling new logic architectures. Future research will likely explore scaling the co‑crystallization process, tuning the additive chemistry, and coupling these chiral spin filters with flexible substrates for wearable spintronic applications.