Hirshfeld Surfaces Identify Inadequacies in Computations of Intermolecular Interactions in Crystals: Pentamorphic 1,8-Dihydroxyanthraquinone

Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the deficiencies in various methodologies employed in the determination of the relative energies of five polymorphs of 1,8-dihydroxyanthraquinone. Nine crystallographically independent molecules were characterized by X-ray crystallography and Hirshfeld surfaces were derived from the X-ray structures. The space groups and number of independent molecules (Z′) for each of the polymorphs (1−5) is as follows: (1) P41 (or P43),Z′ = 1; (2) Pca21, Z′ = 2; (3) P1̅, Z′ = 4; (4) P21/n, Z′ = 1; (5) P41212 (or P43212), Z′ = 0.5. Form 1 is the most thermodynamically stable among the reproducible structures, as established by competitive solubility tests, followed by 2 and then 4. The unrestrained structures of the five polymorphs were computed using the CVFF and COMPASS force fields as well as with the density functional code, SIESTA.

本研究采用希尔施费尔德表面（Hirshfeld surfaces）指纹图谱，定位并分析了多种用于测定1,8-二羟基蒽醌五种多晶型相对能量的方法存在的不足。通过X射线晶体学表征了9个晶体学独立分子，希尔施费尔德表面则由这些X射线结构衍生得到。五种多晶型（1−5）的空间群及独立分子数（Z′）如下：（1）P4₁（或P4₃），Z′=1；（2）Pca2₁，Z′=2；（3）P1̄，Z′=4；（4）P2₁/n，Z′=1；（5）P4₁2₁2（或P4₃2₁2），Z′=0.5。经竞争性溶解度实验证实，晶型1在可重现的结构中热力学稳定性最高，其次为晶型2，随后是晶型4。五种多晶型的无约束结构分别通过CVFF、COMPASS力场以及密度泛函程序SIESTA完成计算。