作者:Gian Maria Dell'Anna、Rita Annunziata、Maurizio Benaglia、Giuseppe Celentano、Franco Cozzi、Oscar Francesconi、Stefano Roelens
DOI:10.1039/b910921h
日期:——
Monotopic and ditopic tripodal benzene platforms featuring aromatic and perfluoroaromatic side-arms have been synthesized, and their binding properties toward C60-fullerene have been investigated by HPLC examining retention times on a fullerene-modified silica stationary phase, using highly polar eluants (acetonitrile and acetonitrile/water). By comparison of structurally homogeneous sets of receptors, a clear trend could be found, pointing to an increased retention for ditopic derivatives, in which binding can occur on both sides of the benzene platform, over their monotopic counterparts. Among the latter, monotopic receptors containing H-substituted aromatic residues showed stronger retention than their perfluorinated analogues. This effect was ascribed to the greater availability of the π-electrons in a H-substituted aromatic ring with respect to the corresponding F-substituted counterpart in participating in a π–π interaction with the electron-poor surface of fullerene. Several NMR experiments aimed to investigate binding interactions in solution, using the much less polar solvents required by the fullerene solubility (1,1,2,2-tetrachloroethane, chloroform, toluene, and CS2), did not provide any evidence of binding interactions. We concluded that π–π interactions between fullerene and the investigated flexible tripodal receptors cannot compete with solvation in poorly polar solvents, and that the binding interactions observed by HPLC were essentially forced by the strongly polar eluant employed for the HPLC analysis.
合成了具有芳香和全氟芳香侧链的单位及双单位三足苯平台,并通过高效液相色谱(HPLC)研究了其与C60富勒烯的结合性能,通过在富勒烯修饰的硅静相上检查保留时间,使用高极性洗脱剂(乙腈和乙腈/水)。在结构均一的受体集合体的比较中,发现了一个明显的趋势,表明双单位衍生物的保留率高于单单位衍生物,因为在双单位中,结合可以发生在苯平台的两侧。在单单位中,含有氢取代芳香基的单单位受体的保留率强于其全氟化类似物。这一效应归因于氢取代芳香环中π电子的更高可用性,相较于相应的氟取代物,在与电子贫乏的富勒烯表面进行π–π相互作用时的参与。几项NMR实验旨在研究溶液中的结合相互作用,使用富勒烯溶解度所需的极性较小的溶剂(1,1,2,2-四氯乙烷、氯仿、甲苯和CS2),但没有提供任何结合相互作用的证据。我们得出结论,富勒烯与所研究的柔性三足受体之间的π–π相互作用无法与极性较差溶剂中的溶剂化竞争,而HPLC观察到的结合相互作用实质上是由于进行HPLC分析时所用的强极性洗脱剂所导致的。