Roshal Alexander D, Sikorski Artur, Baumer Vyacheslav N, Novikov Alexander I, Błazejowski Jerzy
Institute of Chemistry, V. N. Karazin Kharkiv National University, Svoboda Square 4, 60177 Kharkiv, Ukraine.
Acta Crystallogr C. 2007 Nov;63(Pt 11):o626-30. doi: 10.1107/S0108270107039558. Epub 2007 Oct 13.
Crystallization (from ethyl acetate solution) of 2-(4-chlorophenyl)-4-methylchromenium perchlorate, C(16)H(12)ClO(+).;ClO(4)(-), (I), yields two monoclinic polymorphs with the space groups P2(1)/n [polymorph (Ia)] and P2(1)/c [polymorph (Ib)]; in both cases, Z = 4. Cations and anions, disordered in polymorph (Ib), form ion pairs in both polymorphs as a result of Cl-O...pi interactions. Related by a centre of symmetry, neighbouring ion pairs in polymorph (Ia) are linked via pi-pi interactions between cationic fragments, and the resulting dimers are linked through a network of C-H...O(perchlorate) interactions between adjacent cations and anions. The ion pairs in polymorph (Ib), arranged in pairs of columns along the a axis, are linked through a network of C-H...O(perchlorate), C-Cl...pi, pi-pi and C-Cl...O(perchlorate) interactions. The aromatic skeletons in polymorph (Ia) are parallel in the cationic fragments involved in dimers, but nonparallel in adjacent ion pairs not constituting dimers. In polymorph (Ib), these skeletons are parallel in pairs of columns, but nonparallel in adjacent pairs of columns; this is visible as a herring-bone pattern. Differences in the crystal structures of the polymorphs are most probably the cause of their different colours.
高氯酸2-(4-氯苯基)-4-甲基铬盐，C(16)H(12)ClO(+)·ClO(4)(-)，(I)，（从乙酸乙酯溶液中）结晶得到两种单斜多晶型物，空间群分别为P2(1)/n [多晶型物(Ia)] 和P2(1)/c [多晶型物(Ib)]；两种情况下，Z = 4。在多晶型物(Ib)中无序的阳离子和阴离子，由于Cl-O...π相互作用，在两种多晶型物中均形成离子对。通过对称中心相关联，多晶型物(Ia)中相邻的离子对通过阳离子片段之间的π-π相互作用相连，并且所得的二聚体通过相邻阳离子和阴离子之间的C-H...O(高氯酸盐)相互作用网络相连。多晶型物(Ib)中的离子对沿a轴成对排列成列，通过C-H...O(高氯酸盐)、C-Cl...π、π-π和C-Cl...O(高氯酸盐)相互作用网络相连。多晶型物(Ia)中参与二聚体的阳离子片段中的芳环骨架是平行的，但在不构成二聚体的相邻离子对中是不平行的。在多晶型物(Ib)中，这些骨架在列对中是平行的，但在相邻列对中是不平行的；这表现为一种人字形图案。多晶型物晶体结构的差异很可能是它们颜色不同的原因。
