The intrinsic instability of high-spin (S ≥ 1) organic molecules precludes their practical utility/application. Enabling emergent magnetic, spintronic, and quantum phenomena requires new design principles that overcome instability, enables synthetic manipulation, and combines the electronic and optical properties associated with organic semiconducting materials. Here , we demonstrate the synthesis and characterization of a narrow bandgap, solution-processable, donor-acceptor copolymer that is a ground-state triplet (S = 1) in its neutral form. The extended π-system in conjunction with cross-conjugated ferromagnetic coupling units along the polymer backbone results in open-shell character and an inversion of the singlet-triplet energy levels. Electron spin resonance (ESR) and superconducting quantum interference device (SQUID) magnetometry indicate a small high-to-low spin energy gap (ΔEST = 9.30 x 10-3 kcal mol-1) with positive exchange coupling (J = 1.62 cm-1). Our results demonstrate new molecular design guidelines toward stable, high-spin organic semiconductors with unique spin-spin interactions and magnetic properties.

High-spin (S = 1) conjugated copolymer with a paramagnetic ground-state

255th National Meeting (2018)

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