Zeller Matthias, Stouffer Jake L, Solomon Virgil C, Curtin Larry S
Department of Chemistry, Youngstown State University, One University Plaza, Youngstown, OH 44555, USA.
Acta Crystallogr C. 2011 Oct;67(Pt 10):o397-404. doi: 10.1107/S0108270111035797. Epub 2011 Sep 28.
The title compound, C(7)H(4)N(2)O(6), (I), crystallizes in P1 with Z' = 4, but with no approximate or pseudosymmetry. The crystals were nonmerohedrally twinned, with at least four twin components related to the major moiety by 180° rotations around the real b and c axes, and by 180° rotation around the a* axis. The excessive twinning is not caused by a phase change from an untwinned room-temperature higher-symmetry polymorph. The molecules are planar chiral and, owing to the tilt angle of the nitro groups and the position of protonation, there are altogether eight conformers possible. Six of these theoretically possible eight conformers are realized in the solid-state structure of (I). Packing analysis and force-field calculations indicate that the largest part of the packing interactions does not originate from the hydrogen-bonding interactions, as one might initially be tempted to assume; π-π stacking and O(nitro)···π interactions between neighboring molecules of (I) seem to be the dominant factor that determines the packing observed in the structure of this nitro-substituted benzoic acid derivative.
标题化合物C(7)H(4)N(2)O(6)，即(I)，以P1空间群结晶，Z' = 4，且不存在近似或假对称。晶体为非merohedrally孪晶，至少有四个孪晶组分，它们与主要部分通过围绕实际b轴和c轴旋转180°以及围绕a*轴旋转180°相关。过度孪晶并非由未孪晶的室温高对称多晶型的相变引起。分子是平面手性的，由于硝基的倾斜角和质子化位置，总共可能有八种构象。在(I)的固态结构中实现了这八种理论上可能的构象中的六种。堆积分析和力场计算表明，堆积相互作用的最大部分并非如最初可能认为的那样源自氢键相互作用；(I)相邻分子之间的π-π堆积和O(硝基)···π相互作用似乎是决定该硝基取代苯甲酸衍生物结构中观察到的堆积的主要因素。
