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首页> 外文期刊>Journal of Chemical Crystallography >The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives
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The Role of Halogen Bonding in Crystal Structures of 3-Halogeno Cytisine Derivatives

机译：卤素键在3-卤代胱氨酸衍生物晶体结构中的作用

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摘要

The crystal structures of three 3-halogeno derivatives of 13N-substituted cytisine have been determined by X-ray diffraction. The two 13-acetyl substituted compounds, 3-bromo (1) and 3-iodo (2) are isostructural, with the isostructurality index as high as 99%. They both crystallize in monoclinic P21 space group, with unit cell parameters of a = 8.4709(10) Å, b = 9.2266(12) Å, c = 8.6051(10) Å, β = 98.528(11)º (1) and a = 8.2322(6) Å, b = 9.1724(7) Å, c = 8.5494(6) Å, β = 98.181(7)º (2). In turn, 3-bromo-13-t-butyl-carbonate derivative (3) crystallizes in orthorhombic P212121 space group with a = 6.8171(3) Å, b = 7.8994(4) Å, c = 31.4657(15) Å. Conformation of the cytisine skeleton is similar in all three molecules, with almost planar A ring, sofa conformation of B-ring and C ring being an almost ideal chair. However, the orientations of the double C=O bonds in 13N-substituents are completely different: in 1 and 2 it is cis with respect to C12 (C12-N13-C14-O15 torsion angle is 3.3(4)º in 1 and 1.3(6)º in 2) while in 3 it is trans (−175.4(3)º). In the structures of 1 and 2 the driving force of the crystal architecture are quite strong C–H···X halogen bonds with C···X distances far shorter than the sums of van der Waals radii (C···Br in 1 is 2.9430(19) Å and C···I in 2 2.974(3)). In contrast in 3–partially as the consequence of different orientation of the substituent—there are no halogen bondings but instead some weak C–H···O contacts organize the molecules into two-dimensional patterns.
机译：已经通过X射线衍射确定了13N-取代的胱氨酸的三种3-卤代衍生物的晶体结构。两种13-乙酰基取代的化合物3-溴（1）和3-碘（2）是同构的，同构指数高达99％。它们都在单斜P21 空间群中结晶，其晶胞参数为a = 8.4709（10）Å，b = 9.2266（12）Å，c = 8.6051（10）Å，β= 98.528（11）º（ 1）和a = 8.2322（6）Å，b = 9.1724（7）Å，c = 8.5494（6）Å，β= 98.181（7）º（2）。反过来，3-溴-13-叔丁基碳酸酯衍生物（3）在正交晶体P21 21 21 空间群中结晶，其a = 6.8171（3）Å，b = 7.8994 （4），c = 31.4657（15）。在所有三个分子中，胱氨酸骨架的构型都相似，几乎是平面的A环，B环和C环的沙发构型几乎是理想的椅子。但是，在13N取代基中双C = O键的方向完全不同：在1和2中，相对于C12是顺式的（1和1.3中的C12-N13-C14-O15扭转角为3.3（4）º （2）中的（6）º，而在3中则是反式（−175.4（3）º）。在1和2的结构中，晶体结构的驱动力是很强的C–H···X卤素键，其C···X的距离比范德华半径之和（C···Br in 1在2 2.974（3）中为2.9430（19）Å和C··I）。相反，在3中，部分原因是取代基的方向不同-没有卤素键，而是一些弱的C–H··O接触将分子组织成二维模式。

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