Sulfoniumcalixpyrrole: the decoration of a calix[4]pyrrole host with positive charges boosts affinity and selectivity of anion binding in DMSO solvent
作者:Martin Valik、Vladimir Král、Eberhardt Herdtweck、Franz P. Schmidtchen
DOI:10.1039/b617465e
日期:——
With the goal to improve host–guest binding affinity, while retaining guest selectivity, the parent calixpyrrole artificial receptor unit was decorated with four sulfonium moieties (e.g.3b) placed rigidly in symmetrical fashion remote from the core binding site. The determination of binding constants using isothermal titration calorimetry (ITC), in conjunction with trend analyses in a series of related anions, reveals the occurrence of several specific and unspecific binding steps. The former predominate in affinity by 20–1000 fold depending on guest charge and structure. The dissection of the free energy of association into its enthalpic and entropic parts, in combination with structural variation in the guest anion, offers insight into the nature and diversity of the guest binding modes. On these grounds, the supplementation of parent host scaffolds with rigidly positioned positive charge centers, holds promise as a general concept for anion binding in competitive media.
为了在保留客体选择性的同时提高主-客体结合亲和力,在母卡利吡咯人工受体单元上装饰了四个锍分子(如 3b),这些锍分子以对称的方式刚性放置,远离核心结合位点。使用等温滴定量热法(ITC)测定结合常数,并结合一系列相关阴离子的趋势分析,揭示了几个特异性和非特异性结合步骤。根据客体电荷和结构的不同,前者的亲和力要高出 20-1000 倍。结合客体阴离子的结构变化,将结合自由能分解为焓和熵两部分,有助于深入了解客体结合模式的性质和多样性。有鉴于此,在母体宿主支架上添加刚性定位的正电荷中心,有望成为竞争性介质中阴离子结合的一般概念。