Gardner Joseph S, Conda-Sheridan Martin, Smith Dana N, Harrison Roger G, Lamb John D
Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602-5700, USA.
Inorg Chem. 2005 Jun 13;44(12):4295-300. doi: 10.1021/ic048841k.
Anion binding has been achieved with a resorcinarene substituted with four 2,2'-dipicolylamine moieties on the upper rim. The four dipicolylamine groups reside in proximity on one rim of the cavitand. The dipicolylamine groups were protonated with triflic acid to provide the cationic ammonium sites for anion binding. This anion receptor binds strongly to anions of different geometries, such as H(2)PO(4)(-), Cl(-), F(-), CH(3)CO(2)(-), HSO(4)(-), and NO(3)(-). The association constants for binding these anions are large, on the order of log K = 5 in CD(3)CN, a solvent of intermediate dielectric constant. These values represent significant binding compared to other cavitands with nitrogen pendant groups. Evidence suggests that the cavitand provides two identical receptor sites formed by two dipicolylamine groups, facilitating the simultaneous binding of two anions. Intramolecular binding of anions between two protonated dipicolylamine groups is indicated on the basis of the comparison to a structurally similar monomeric analogue and by semiempirical PM3 molecular modeling. Titrations with the analogue result in much weaker anion association, even at high concentrations, indicating the importance of proximity and preorganization of sites on the cavitand upper rim.
在上缘带有四个2,2'-联吡啶甲胺基团的间苯二酚杯芳烃实现了阴离子结合。四个联吡啶甲胺基团位于空穴化合物一侧边缘的附近位置。用三氟甲磺酸将联吡啶甲胺基团质子化，以提供用于阴离子结合的阳离子铵位点。这种阴离子受体能与不同几何形状的阴离子强烈结合，如H(2)PO(4)(-)、Cl(-)、F(-)、CH(3)CO(2)(-)、HSO(4)(-)和NO(3)(-)。在介电常数适中的溶剂CD(3)CN中，结合这些阴离子的缔合常数很大，约为log K = 5。与其他带有氮侧基的空穴化合物相比，这些值代表了显著的结合作用。有证据表明，空穴化合物提供了由两个联吡啶甲胺基团形成的两个相同的受体位点，便于同时结合两个阴离子。与结构相似的单体类似物比较以及通过半经验PM3分子模型表明，两个质子化的联吡啶甲胺基团之间存在阴离子的分子内结合。用该类似物进行滴定，即使在高浓度下，阴离子缔合也弱得多，这表明空穴化合物上缘位点的接近度和预组织的重要性。
