Being a close analogue of amflutizole, methyl 4‐amino‐3‐phenylisothiazole‐5‐carboxylate (C₁₁H₁₀N₂O₂S) was assumed to be capable of forming polymorphic structures. Noncentrosymmetric and centrosymmetric polymorphs have been obtained by crystallization from a series of more volatile solvents and from denser tetrachloromethane, respectively. Identical conformations of the molecule are found in both structures. The two polymorphs differ mainly in the intermolecular interactions formed by the amino group and in the type of stacking interactions between the π‐systems. The most effective method for revealing packing motifs in structures with intermolecular interactions of different types (hydrogen bonding, stacking, dispersion, etc.) is to study the pairwise interaction energies using quantum chemical calculations. Molecules form a column as the primary basic structural motif due to stacking interactions in both polymorphic structures under study. The character of a column (straight or zigzag) is determined by the orientations of the stacked molecules (in a `head‐to‐head' or `head‐to‐tail' manner). Columns bound by intermolecular N—H…O and N—H…N hydrogen bonds form a double column as the main structural motif in the noncentrosymmetric structure. Double columns in the noncentrosymmetric structure and columns in the centrosymmetric structure interact strongly within the ab crystallographic plane, forming a layer as a secondary basic structural motif. The noncentrosymmetric structure has a lower density and a lower (by 0.59 kJ mol⁻¹) lattice energy, calculated using periodic calculations, compared to the centrosymmetric structure.

中文翻译：

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4-氨基-3-苯基异噻唑-5-羧酸甲酯的多态性：一项实验和理论研究

作为安氟替唑的类似物，可以认为4-氨基-3-苯基异噻唑-5-羧酸甲酯（C ₁₁ H ₁₀ N ₂ O ₂ S）能够形成多晶型结构。非中心对称和中心对称多晶型物已分别通过从一系列更具挥发性的溶剂和较浓的四氯甲烷中结晶而获得。在两个结构中都发现了分子的相同构象。这两种多晶型物的主要区别在于氨基形成的分子间相互作用和π系统之间的堆积相互作用类型。显示具有不同类型的分子间相互作用（氢键，堆积，分散，等。）是使用量子化学计算研究成对相互作用的能量。由于正在研究的两个多态结构中的堆积相互作用，分子形成圆柱作为主要的基本结构基序。列的特性（直的或锯齿形的）由堆叠分子的方向（以“头对头”或“头对尾”的方式）确定。由分子间NH-OH和NH-N氢键结合的柱形成双柱，作为非中心对称结构中的主要结构基序。非中心对称结构中的双列和中心对称结构中的列在ab内强烈相互作用结晶平面，形成一层作为次级基本结构图案。与中心对称结构相比，使用周期性计算所计算出的非中心对称结构具有更低的密度和更低的晶格能量（降低了0.59 kJ mol ^-1）。