The first in situ preparation and single-crystal structure identification of pure 1-(pyridin-4-yl)-4-thiopyridine (PTP), C₁₀H₈N₂S, a simple and basic derivative of mercaptopyridine, from a crystallization mixture is described. The same PTP was found in two multicomponent crystal forms with 3,5-dinitrobenzoic acid as a classic two-component cocrystal, namely, 1-(pyridin-4-yl)-4-thiopyridine–3,5-dinitrobenzoic acid (1/1), C₇H₄N₂O₆·C₁₀H₈N₂S, and with 2-hydroxy-3,5-dinitrobenzoic acid as a salt formed via proton transfer from the hydroxy group of the acid to the pyridyl N atom of PTP, namely, 4-(4-sulfanylidene-1,4-dihydropyridin-1-yl)pyridin-1-ium 1-carboxy-3,5-dinitrophenolate, C₁₀H₉N₂S⁺·C₇H₃N₂O₇⁻. The protonation energy of PTP is 944.64 kJ mol⁻¹, indicating slightly greater N-basicity compared to pyridine, a well characterized and very basic chemical reference. A variety of molecular interactions can be observed in the three new crystal structures of PTP, which are all discussed in detail. Our findings confirm those of previous studies, indicating that PTP and 4-mercaptopyridine may, under suitable conditions, be chemically converted to one another, and that this process can be stimulated by light (UV–Vis).

中文翻译：

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结晶状态的 1-(吡啶-4-基)-4-硫代吡啶 (PTP) – 纯 PTP 以及共晶体和盐

首次从结晶混合物中原位制备纯 1-(吡啶-4-基)-4-硫代吡啶 (PTP)，C ₁₀ H ₈ N ₂ S（一种简单的碱性巯基吡啶衍生物）并进行单晶结构鉴定被描述。在两种多组分晶型中发现了相同的 PTP，其中 3,5-二硝基苯甲酸作为经典的双组分共晶，即 1-(吡啶-4-基)-4-硫代吡啶–3,5-二硝基苯甲酸 (1/ 1)、C ₇ H ₄ N ₂ O ₆ ·C ₁₀ H ₈ N ₂ S，与2-羟基-3,5-二硝基苯甲酸通过质子从酸的羟基转移至吡啶基N形成盐PTP原子，即4-(4-亚硫基-1,4-二氢吡啶-1-基)吡啶-1-鎓1-羧基-3,5-二硝基苯酚盐，C ₁₀ H ₉ N ₂ S ⁺ ·C ₇ H ₃ N ₂ O ₇ ^-。PTP 的质子化能为 944.64 kJ mol ^-1，表明与吡啶相比，N-碱度略高，吡啶是一种充分表征且非常基本的化学参考。在 PTP 的三种新晶体结构中可以观察到多种分子相互作用，并对这些结构进行了详细讨论。我们的研究结果证实了之前的研究结果，表明 PTP 和 4-巯基吡啶可以在适当的条件下相互化学转化，并且这一过程可以通过光（紫外-可见光）刺激。