The X-ray structures of three new 1:1 pharmaceutical cocrystals of 11-azaartemisinin (11-Aza; systematic name: 1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.0^4,13.0^8,13]hexadecan-10-one, C₁₅H₂₃NO₄) with bromo-substituted salicylic acids [namely, 5-bromo- (5-BrSalA, C₇H₅BrO₃), 4-bromo- (4-BrSalA, C₇H₅BrO₃) and 3,5-dibromosalicylic acid (3,5-Br₂SalA, C₇H₄Br₂O₃)] are reported. All the structures are related to the parent 11-Aza:SalA cocrystal (monoclinic P2₁) reported previously. The 5-BrSalA analogue is isostructural with the parent, with lattice expansion along the c axis. The 4-BrSalA and 3,5-Br₂SalA cocrystals retain the highly preserved 2₁ stacks of the molecular pairs, but these pack with a varying degree of slippage with respect to neighbouring stacks, altering the close contacts between them, and represent two potential alternative homostructural arrangements for the parent compound. Structure redeterminations of the bromosalicylic acids 5-BrSalA, 4-BrSalA and 3,5-Br₂SalA at 100 K show that the packing efficiency of the cocrystals need not be higher than the parent coformers, based on specific-volume calculations, attributable to the strong O—H…O=C hydrogen bonds of 2.54 Å in the cocrystals.

中文翻译：

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一系列抗疟药11-氮杂青蒿素与水杨酸共晶的不同程度的同质性

11-氮杂青蒿素（11-Aza；系统名称：1,5,9-trimethyl-14,15,16-trioxa-11-azatetracyclo[10.3.1.0 ^{4, 13} .0 ^8,13 ]十六烷-10-one, C ₁₅ H ₂₃ NO ₄ ) 与溴取代的水杨酸 [即 5-溴- (5-BrSalA, C ₇ H ₅ BrO ₃ ), 4-溴- (4-BrSalA, C ₇ H ₅ BrO ₃ ) 和 3,5-二溴水杨酸 (3,5-Br ₂ SalA, C ₇ H ₄ Br ₂ O ₃)] 报道。所有结构都与先前报道的母体 11-Aza:SalA 共晶（单斜P 2 ₁）有关。5-BrSalA 类似物与母体同构，沿c轴晶格膨胀。4-BrSalA 和 3,5-Br ₂ SalA 共晶保留了高度保存的 2 ₁分子对叠层，但它们相对于相邻叠层具有不同程度的滑动，改变了它们之间的紧密接触，并代表了两个母体化合物的潜在替代同构排列。溴水杨酸 5-BrSalA、4-BrSalA 和 3,5-Br _{2 的}结构重新测定萨拉在100K表明，共结晶的包装效率需要不大于亲本更高的助形成物，是根据特定体积计算，归因于共结晶2.54埃的强O - H ... O = C氢键。