Benzobis(imidazolium)-Cucurbit[8]uril Complexes for Binding and Sensing Aromatic Compounds in Aqueous Solution
Benzobis(imidazolium)-Cucurbit[8]uril Complexes for Binding and Sensing Aromatic Compounds in Aqueous Solution
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DOI：
10.1002/chem.201002274
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发表时间：
2010-12-01
影响因子：
4.3
通讯作者：
Scherman, Oren A.
中科院分区：
文献类型：
--
作者：
Biedermann, Frank;Rauwald, Urs;Scherman, Oren A.
描述了苯并双（咪唑）盐（BBIs）作为涉及大环宿主瓜b[8] （CB[8]）的超分子组装体的稳定和荧光成分的效用。CB[8]在水介质中具有选择性地与两种不同的客体紧密结合的能力，通常是甲基紫紫素（MV）作为第一客体，其次是吲哚、萘或含儿茶酚的第二客体。基于相似的大小、形状和电荷，四甲基苯并双胍（咪唑）（MBBI）被确定为MV的潜在替代品，可以增加葫芦b[8] uril的客人曲目。等温滴定量热法（ITC）研究表明，MBBI与CB[8]以1:1的比例结合，平衡结合常数（K-a）为5.7 x 10(5) M-1。CB[8]配合物与一系列K-a值在10(3)到10(5)M-1之间的芳香二客体结合。这些络合现象得到了质谱分析的支持，证实了络合的形成，并且一系列的核磁共振研究显示了预期的芳香峰和MBBI甲基峰的上场扰动。令人惊讶的是，MBBI的结合行为与MV惊人地相似，但MBBI在许多应用中提供了许多实质优势，包括固有荧光，高化学稳定性和广泛的合成可调性。的确，MBBI的强烈荧光发射。CB[8]配合物在与第二客体结合时被淬灭，从而证明了MBBI作为光学传感元件的实用性。在这些有利属性的基础上，MBBI。CB -[8]系统成功地应用于多肽的序列选择性识别以及水中聚合物聚集体的受控分解。这些结果拓宽了葫芦[n]南瓜家族的可用客人，并展示了潜在的新应用。
The utilities of benzobis(imidazolium) salts (BBIs) as stable and fluorescent components of supramolecular assemblies involving the macrocyclic host, cucurbit[8]uril (CB[8]), are described. CB[8] has the unusual ability to bind tightly and selectively to two different guests in aqueous media, typically methyl viologen (MV) as the first guest, followed by an indole, naphthalene, or catechol-containing second guest. Based on similar size, shape, and charge, tetramethyl benzobis(imidazolium) (MBBI) was identified as a potential alternative to MV that would increase the repertoire of guests for cucurbit[8] uril. Isothermal titration calorimetry (ITC) studies showed that MBBI binds to CB[8] in a 1: 1 ratio with an equilibrium association constant (K-a) value of 5.7 x 10(5) M-1, and that the resulting MBBI.CB[8] complex binds to a series of aromatic second guests with K-a values ranging from 10(3) to 10(5) M-1. These complexation phenomena were supported by mass spectrometry, which confirmed complex formation, and a series of NMR studies that showed the expected upfield perturbation of aromatic peaks and of the MBBI methyl peaks. Surprisingly, the binding behavior of MBBI is strikingly similar to that of MV, and yet MBBI offers a number of substantial advantages for many applications, including intrinsic fluorescence, high chemical stability, and broad synthetic tunability. Indeed, the intense fluorescence emission of the MBBI.CB[8] complex was quenched upon binding to the second guests, thus demonstrating the utility of MBBI as a component for optical sensing. Building on these favorable properties, the MBBI.CB[8] system was successfully applied to the sequence-selective recognition of peptides as well as the controlled disassembly of polymer aggregates in water. These results broaden the available guests for the cucurbit[n]uril family and demonstrate potentially new applications.