分子间卤键控制的氢键芳香酰胺折叠体组装

Intermolecular Halogen Bonding-Controlled Self-Assembly of Hydrogen Bonded Aromatic Amide Foldamers

报道了六个分子内氢键诱导的芳香酰胺折叠体的合成,其多步合成中最后一步都通过形成腙键完成.所有分子的两端都引入三氟一碘代苯作为卤键供体及吡啶作为卤键受体.分子间形成的I…N卤键及其它卤键被用于调控折叠体骨架在固体中的自组装结构.晶体结构揭示,分子间卤键可以诱导不同分子形成扩展的之字形阵列,二聚体大环和超分子螺旋结构.当分子两端的卤键供体和受体平行排列时,折叠体倾向于形成超分子二聚体大环.长的四聚体和五聚体折叠结构两端的卤键供体和受体形成大的夹角,展示出不同的卤键模式.两个分子的端位碘原子与甲醇或水形成I…O卤键,其中一个五聚体分子与甲醇通过卤键形成超分子单股螺旋结构.另一个五聚体通过分子间I…O=C卤键形成另一种超分子单股螺旋.两个单股螺旋进一步相互堆积,形成新的超分子双股螺旋阵列.

Six intramolecular hydrogen bonding-induced aromatic amide foldamers have been prepared through the formation of the hydrazone bond in the last step.The compounds are attached with one trifluoroiodobenzene as halogen donor and one pyridine ring as halogen bonding acceptor.Intermolecular I…N halogen bond formed by the above two units and other kinds of halogen bonds are designed to modulate the stacking of the compounds in the solid state.It is revealed that intermolecular halogen bonding can induce the molecules to form extended zigzag arrays,dimeric macrocycles or supramolecular helices.The formation of the dimeric macrocycles is favored when the halogen bond donor and acceptor are located in a parallel manner.Longer tetrameric and pentameric sequences give rise to more curved,crescent conformations,with the two halogen bonding donor and acceptor on the ends to form a large angle.For two compounds,polar methanol or water prevents the formation of the intermolecular end-to-end halogen bonding by forming I…O halogen bonding.The pentameric compound is connected by methanol to form supramolecular single helices.For another pentameric compound,strong I…O=C halogen bonding is found to induce the backbone to self-assemble into supramolecular single helices.The single helices further stack to afford supramolecular double helix arrays.