The Z and E isomers of 3-[4-(dimethylamino)phenyl]-2-(2,4,6-tribromophenyl)acrylonitrile, C17H13Br3N2, (1), were obtained simultaneously by a Knoevenagel condensation between 4-(dimethylamino)benzaldehyde and 2-(2,4,6-tribromophenyl)acetonitrile, and were investigated by X-ray diffraction and density functional theory (DFT) quantum-chemical calculations. The (Z)-(1) isomer is monoclinic (space group P21/n, Z′ = 1), whereas the (E)-(1) isomer is triclinic (space group P\overline1}, Z′ = 2). The two crystallographically-independent molecules of (E)-(1) adopt similar geometries. The corresponding bond lengths and angles in the two isomers of (1) are very similar. The difference in the calculated total energies of isolated molecules of (Z)-(1) and (E)-(1) with DFT-optimized geometries is ∼4.47 kJ mol−1, with the minimum value corresponding to the Z isomer. The crystal structure of (Z)-(1) reveals strong intermolecular nonvalent Br...N [3.100 (2) and 3.216 (3) Å] interactions which link the molecules into layers parallel to (10\overline1}). In contrast, molecules of (E)-(1) in the crystal are bound to each other by strong nonvalent Br...Br [3.5556 (10) Å] and weak Br...N [3.433 (4) Å] interactions, forming chains propagating along [110]. The crystal packing of (Z)-(1) is denser than that of (E)-(1), implying that the crystal structure realized for (Z)-(1) is more stable than that for (E)-(1).
通过 4-(二甲基氨基)苯甲醛和 2-(2,4,6-三溴苯基)乙腈之间的克诺文纳格尔缩合反应,同时得到了 3-[4-(二甲基氨基)苯基]-2-(2,4,6-三溴苯基)丙烯腈(C17H13Br3N2,(1))的 Z 和 E 异构体,并通过 X 射线衍射和密度泛函理论(DFT)量子化学计算对其进行了研究。(Z)-(1)异构体为单斜晶系(空间群为 P21/n,Z′=1),而(E)-(1)异构体为三斜晶系(空间群为 P\overline1} ,Z′=2)。(E)-(1) 的两个晶体学上独立的分子采用相似的几何结构。(1) 的两个异构体中相应的键长和角度也非常相似。在 DFT 优化的几何结构下,(Z)-(1) 和 (E)-(1) 分离分子的计算总能量相差 ∼4.47 kJ mol-1,其中 Z 异构体的计算总能量最小。(Z)-(1)的晶体结构显示了分子间强烈的非价 Br...N [3.100 (2) 和 3.216 (3) Å]相互作用,这种相互作用将分子连接成平行于 (10\overline1}) 的层。相反,晶体中的(E)-(1)分子则通过强的非价 Br...Br [3.5556 (10) Å]和弱的 Br...N [3.433 (4) Å]相互作用相互结合,形成沿 [110] 传播的链。(Z)-(1)的晶体堆积比(E)-(1)的密集,这意味着(Z)-(1)的晶体结构比(E)-(1)的晶体结构更稳定。