It has been confirmed that mercaptopyridines undergo spontaneous condensation in redox reaction with iodine-forming dithiopyridines. In the solid state, these compounds are protonated at the N atoms and cocrystallize with iodine forming salt structures, namely, 2-[(pyridin-2-yl)disulfanyl]pyridinium triiodide sesquiiodine, C₁₀H₉N₂S₂⁺·I₃⁻·1.5I₂, and 4,4′-(disulfanediyl)dipyridinium pentaiodide triiodide, C₁₀H₁₀N₂S₂²⁺·I₅⁻·I₃⁻. Dithiopyridine cations are packed among three-dimensional frameworks built from iodide anions and neutral iodine molecules, and are linked by hydrogen, halogen and chalcogen interactions. Quantum chemical computations indicated that dithiopyridines exhibit anomalously high nitrogen basicity which qualify them as potential proton sponges.

中文翻译：

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二硫代双吡啶的离子共晶：I…I 卤素键在构建碘骨架和稳定晶体结构中的作用

已经证实巯基吡啶在氧化还原反应中与形成碘的二硫代吡啶发生自发缩合。在固态下，这些化合物在 N 原子处质子化并与碘共结晶形成盐结构，即 2-[(pyridin-2-yl)disulfanyl]pyridinium triiodide sesquiiodine, C ₁₀ H ₉ N ₂ S ₂ ⁺ ·I ₃ ^- ·1.5I ₂和 4,4'-(二硫烷二基)二吡啶鎓五碘化物，C ₁₀ H ₁₀ N ₂ S ₂ ²⁺ ·I ₅ ^- ·I ₃ ^-. 二硫代吡啶阳离子被填充在由碘阴离子和中性碘分子构建的三维框架中，并通过氢、卤素和硫属元素相互作用连接。量子化学计算表明，二硫代吡啶表现出异常高的氮碱度，这使它们成为潜在的质子海绵。