Charge-Resonance Polymerization at Donor-Acceptor Interfaces Enables Large-Area Organic Magnetic Membranes

Electron acceptors such as tetracyanoquinodimethane (TCNQ) and its fluorinated analogue F4TCNQ are foundational to charge-transfer and doping chemistry. At interfaces formed by deposition of these acceptors onto donor substrates, reduced anionic species can naturally coexist with unreacted neutral acceptors, creating mixed-valence environments beyond conventional one-way charge transfer. Here, we report charge-resonance polymerization of acceptors at donor-acceptor interfaces. Deposition of neutral acceptors onto electron-donor substrates partially reduces the acceptors to anion salts, establishing neutral/radical-anion contact. This mixed-valence interface enables cyclic neutral-anion charge-resonance interactions that initiate a self-propagating polymerization process. This dynamic process operates across diverse donor substrates and from room temperature to 250 °C, producing large-area membranes up to 30 × 30 cm with persistent radicals and room-temperature magnetic hysteresis. These findings establish intraspecies charge resonance as a design principle for self-activating polymerization and offer fresh insight into charge behavior at donor-acceptor interfaces.