Hydrogen‐Bonding Order Associated With Radical Delocalization in Layered Organic Cathode Materials

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Abstract
Organic electrode materials (OEMs) offer a sustainable alternative to inorganic cathodes but typically suffer from low intrinsic electronic conductivity. The material historically reported as bis‐tetraaminobenzoquinone (TAQ) exhibits bulk conductivity two orders of magnitude higher than its close analogue tetraaminophenazine‐tetraone (TAPT), despite their common precursor and nearly identical short‐range structure. This disparity has previously been attributed to distinct molecular skeletons, with TAQ proposed to adopt a piperazine‐type linkage and TAPT a pyrazine ring. Here, combining synchrotron x‐ray scattering, solid‐state 15 N and 13 C nuclear magnetic resonance (NMR), microcrystal electron diffraction (MicroED), continuous‐wave and pulsed electron paramagnetic resonance (EPR) spectroscopy, we show that “TAQ” has the same pyrazine‐based molecular structure as TAPT, with no evidence for piperazine core or keto–enol tautomerization. Their key difference lies in synthesis‐dependent degree of crystallinity: “TAQ” exhibits greater long‐range structural coherence and a crystallographically resolved intermolecular hydrogen‐bonding network, whereas TAPT is more disordered. EPR further shows that the higher structural order in “TAQ” is associated with a strongly delocalized π‐spin manifold, while TAPT favors localized or weakly delocalized radicals and stronger local spin coupling. These findings identify degree of crystallinity and hydrogen‐bonding order as key structural features associated with radical delocalization and enhanced conductivity in organic electrodes.
Funding Information
  • U.S. Department of Energy (DE‐AC02‐06CH11357)
  • U.S. Department of Energy (DE‐SC0024064)

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