基于分子间卤键的超分子平面大环自组装

Self-assembly of Supramolecular Planar Macrocycle Driven by Intermolecular Halogen Bonding

本工作报道了含卤键供体和受体片段的三种芳酰胺分子(化合物1~3)的设计和合成,并对固相中卤键的不同作用模式进行了探索和分析.化合物1的晶体数据显示,由于没有分子内氢键,组成分子的三个芳环相互扭转一定角度,并且在分子间交替排列的N…I和O…I卤键的控制下,组装成了一条线型的超分子组装体.由于酰胺羰基和两个紧邻的氟原子之间的排斥作用,化合物2未能形成分子内三中心氢键.在此基础上,将三氟碘代苯作为卤键供体片段引入到化合物3中,并且在折叠体骨架中嵌入了嘧啶单元.化合物3的晶体数据显示,基于多组有效的分子内三中心氢键和分子间较强的卤键作用,双分子间形成了[1+1]的超分子大环.另外,由于嘧啶环的引入,使得该超分子大环接近共平面.

The design and synthesis of three kinds of arylamide molecules(compounds 1~3) containing halogen bonding donor and acceptor fragments,and the exploration and analyzation of different action modes of halogen bonding in solid phase were reported.Compounds 1 and 2 contain two tetrafluoroiodobenzene fragments,and compound 1 also contains a halogen receptor fragment—pyridine group.Isobutyl groups are introduced into the molecule to increase its solubility and crystallinity.And a pyrimidine fragment was introduced into compound 3,which has more aromatic rings.The two N atoms of the pyrimidine fragment can theoretically form intramolecular hydrogen bonds with the adjacent amide hydrogen atoms(—C(=O)NH),so that the whole molecule has the properties of hydrogen-bonded arylamide foldamer.Moreover,trifluorobenzene fragments were selected in compound 3 to eliminate the repulsion between excess fluorine atoms and carbonyls.The crystal structures reveal that the three aromatic rings in compound 1 are twisted with each other for there is no intramolecular hydrogen bond,and a supramolecular DNA-like double helix was assembled controlled by intermolecular N…I and O…I halogen bonds arranged alternately.Compound 2 failed to form an intramolecular three-center hydrogen bonding due to the repulsion between the amide carbonyl groups and the two fluorine atoms in close proximity.As expected,in the solid phase of compound 3,an effective three-center hydrogen bond is formed between the terminal trifluoroiodobenzene and the benzene ring attached to it.Moreover,the two N—H bonds connected to the pyrimidine ring also form two effective three-center hydrogen bonds.The difference is that the participants of these two groups of three-center hydrogen bonds include two N atoms in the pyrimidine ring.The four aromatic rings in compound 3 are nearly coplanar driven by these intramolecular three-center hydrogen bonds.Two sets of strong intermolecular(pyridine ring) N…I halogen bonds control the formation of [1+1] bimolecular supramolecular macrocycles with inner diameters of 1.36 nm and 1.07 nm in length and width.Moreover,the supramolecular macrocycle is near-planar due to the introduction of pyrimidine ring.