Knock-on synthesis of tritopic calix[4]pyrrole host for enhanced anion interactions
Knock-on synthesis of tritopic calix[4]pyrrole host for enhanced anion interactions
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DOI：
10.1039/c9dt02365h
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发表时间：
2019-11-07
影响因子：
4
通讯作者：
Hill, Jonathan P.
中科院分区：
文献类型：
--
作者：
Chahal, Mandeep K.;Labuta, Jan;Hill, Jonathan P.
本文报道了一种用区域选择性合成方法制备的三位周边功能化的共轭杯[4]吡咯主体（1）与阴离子客体的相互作用。合成的区域选择性依赖于杯[4]吡咯的选择性N-烷基化，这是由一个吡咯基团的外围取代和随后在相对的吡咯基团上的N-烷基化引起的，我们称之为“敲入”区域选择性。所得的主体分子表现出阴离子与常见的氯离子和硝酸根阴离子的相互作用增强了一个数量级以上的母体共轭杯[4]吡咯。结合分析的H-1 NMR和紫外-可见光谱滴定数据，使评估的结合强度的阴离子与主机K-A的结合模型，其中盐的解离过程也被纳入其解离常数K-d的形式。阴离子可以根据它们与1的相互作用分为两类：A型阴离子（氯离子、硝酸根、高氯酸根、硫酸氢根）通过氢键结合为1：1复合物，而涉及B型阴离子（乙酸根、氟离子、磷酸二氢根）的相互作用则通过主体去质子化和/或抗衡阳离子缔合而复杂化。基于边缘官能化杯[4]吡咯的生色团如1代表了用于估计生物相关阴离子或其他物种的有前途的新生色团家族。
Interactions of anionic guests with a tritopic peripherally functionalized conjugated calix[4]pyrrole host (1) prepared using a regioselective synthetic method is reported. The regioselectivity of synthesis relies on selective N-alkylation of the calix[4]pyrrole caused by peripheral substitution of one pyrrole group with subsequent N-alkylation at the opposing pyrrole group termed by us 'knock-on' regioselectivity. The resulting host molecule exhibits anion interactions with common chloride and nitrate anions enhanced by an order of magnitude over the parent conjugated calix[4]pyrrole. Combined analysis of H-1 NMR and UV-vis spectroscopic titration data enabled an evaluation of binding strengths of anions with the host K-A in a binding model where the salt dissociation process is also incorporated in the form of its dissociation constant K-d. Anions could be classified as two types based on their interactions with 1: Type A anions (chloride, nitrate, perchlorate, hydrogensulphate) associate as 1:1 complexes through hydrogen bonding while interactions involving Type B anions (acetate, fluoride, dihydrogenphosphate) are complicated by host deprotonation and/or countercation association. Hosts based on rim-functionalized calix[4]pyrroles such as 1 represent a promising new family of chromophores for estimation of biologically relevant anions or other species.