Threefold twinning in 1‐{(R)‐1‐[(3‐oxo‐2‐isoindolinoyl)methyl]‐2‐propenyl}‐5‐methyl‐2,3‐indolinedione, C₂₁H₁₆N₂O₄, has been reported recently [Trost et al. (2020). Org. Lett.22, 2584–2589] but the twin characterization was not published. This twinning presents several interesting features. The crystal structure is monoclinic, but its lattice is metrically strongly pseudo‐orthorhombic and underpins a strongly pseudo‐hexagonal sublattice. Several possible twin laws are compatible with these metric specializations, among which the one found experimentally corresponds to a trichromatic point group. Twinning is by reticular pseudo‐merohedry with twin index 2 and zero obliquity but a non‐zero twin misfit. The twin lattice coincides with the pseudo‐hexagonal sublattice of the individual domain, which justifies the adoption of the unconventional setting B2₁ of the space group.

中文翻译：

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1-{（R）-1-[[（3-氧代-2-异吲哚基）甲基] -2-丙烯基] -5-甲基-2,3-吲哚二酮中的零斜双晶格准对称三重孪生。

在1-{（R）-1-[（3-氧代-2-异吲哚基）甲基] -2-丙烯基} -2-甲基-2-，3-吲哚二酮，C ₂₁ H ₁₆ N ₂ O ₄中具有三重孪生最近报道[Trost等。（2020）。单位 来吧 22，2584–2589]，但未公布孪生子特性。孪生呈现了几个有趣的功能。晶体结构是单斜晶的，但其晶格是度量严格的伪正交晶格，并支撑了强烈的伪六边形亚晶格。几种可能的孪生定律与这些度量专长兼容，其中在实验上发现的定律对应于三色点组。孪生是通过网状假体，孪生指数为2，倾角为零，但非零孪生失配。双晶格与单个域的伪六边形子格重合，这证明采用空间组的非常规设置B 2 ₁是合理的。