Calix[4]arenes in the 1,3-alternate conformation (1-3) and bearing activated amide groups at the upper rim have been synthesized and their anion binding properties studied and compared with conformationally mobile (4) or cone (Ib) receptors having the same binding groups. Association constants determined in CDCl3 show a stronger complexation for Y-shaped carboxylate anions and a higher efficiency for receptors (Ib and 3) bearing dichloroacetamido moieties as hydrogen bonding donor groups. Molecular modeling studies performed on the cone derivative (Ib) and its 1,3-alternate isomer (10) and ab initio calculations on 4-methoxyaniline derivatives (11-13) used as simplified models, reveal that the α,α-dichloroacetamido moieties bind anions in a bidentate fashion using both the N-H and the CHCl2 as hydrogen bonding donor groups. This explains the higher efficiency in carboxylate binding found for Ib and 3 that incorporate the dichloroacetamido binding unit in their structures.
Calix[4]arenes在1,3-交替构象(1-3)中,其上缘带有活化酰胺基团已被合成,并研究了它们的阴离子结合性能,并与构象移动的(4)或锥形(Ib)受体进行了比较,这些受体具有相同的结合基团。在CDCl3中测定的结合常数显示,Y形羧酸阴离子的复合作用更强,而对于具有二氯乙酰胺基团作为氢键给体基团的受体(Ib和3),效率更高。对锥形衍生物(Ib)及其1,3-交替异构体(10)进行的分子建模研究以及对作为简化模型使用的4-甲氧基苯胺衍生物(11-13)的从头算计算表明,α,α-二氯乙酰胺基团以双齿方式结合阴离子,同时使用N-H和CHCl2作为氢键给体基团。这解释了在结构中包含二氯乙酰胺基团的Ib和3中发现的对羧酸结合的更高效率。