弯月状寡聚芳酰胺超分子凝胶及其识别客体分子和离子的研究

Currently, smart responsiveness is one of the most significant challenges in developing supramolecular gels, and their abilities to recognize guest molecules or ions have rendered them grow into an important research direction. In the present project, supramolecular gels are prepared based on the assembled crescent aromatic oligoamides with shape-persistent backbones enforced by intramolecular three-center hydrogen bonds. Bases on the concept that external stimulation could induce sensitive changing of gels, studies are conducted involving multiple responsiveness to recognition of biologically essential small molecules (e.g., arginine), environmentally hazardous ions (e.g., mercury) as well as pesticide molecules (e.g., diquat). This system is expected to exhibit selective discrimination of L-arginine from 20 amino acids is realized through observations of single component gel collapsing, and selective recognition of mercury ions from transition metal ions. The host-guest interaction between the supramolecular gel and guest molecules or ions, and the binding site, are probed to reveal the mechanism of gel formation and recognition, thereby understanding the causes of gel collapse inherent within these oligoamide compounds. This project could lead not only to establishing a supramolecular gelation system constructed from a class of crescent hydrogen bonded aromatic oligoamides, but also to paving a way for further molecular design of functional supramolecular gels.

当前凝胶研究面临的最大问题之一是智能响应性，而智能响应性凝胶材料发展的一个重要研究方向是识别客体分子或离子。本项目利用分子内三中心氢键固定的弯月状寡聚芳酰胺化合物制备超分子凝胶，基于凝胶在外界环境刺激下产生的敏感变化，研究此凝胶对重要生物小分子（如精氨酸）、环境有害离子（如汞离子）以及农药分子（如敌草快）的多重响应识别。通过单组分凝胶的塌陷从二十种天然氨基酸中选择性识别精氨酸，并且从过渡金属离子中选择性识别汞离子。对凝胶形成及其识别机理进行探讨，研究主客体作用关系，明确其作用位点，揭示这类寡聚芳酰胺体系凝胶识别客体的内在规律。本项目不仅将建立一类基于分子内氢键固定的寡聚芳酰胺的超分子凝胶体系，而且可为进一步的功能化凝胶设计奠定基础。

本项目利用分子内三中心氢键固定的弯月状寡聚芳酰胺化合物制备了超分子凝胶。通过对侧链的选择，得到了性质优异的单组分凝胶，并对凝胶形成机理进行了探讨。通过XRD实验证实了寡聚芳酰胺之间存在的π-π堆积作用是形成凝胶的主要驱动力之一。研究了此凝胶对环境有害分子（敌草快）和重要生物小分子（精氨酸和细胞色素C）的响应识别。通过二维核磁证实了弯月状寡聚芳酰胺和客体分子的作用位点位于其空腔中，其主要作用力为主体分子上羰基氧与客体分子上的质子的氢键作用。客体分子与主体空腔作用后，由于客体的空间位阻作用，极大地减弱了主体相互之间的π-π堆积作用，导致了凝胶的塌陷。此外，探讨了弯月状寡聚芳酰胺的类似物环芳酰胺与细胞色素C的主客体作用，利用环芳酰胺与细胞色素C形成的复合物作为酶催化剂进行了催化氧化反应。考察了环芳酰胺双组分凝胶对氨基酸的识别，该凝胶体系能通过刺激响应性凝胶塌陷，实现从20种天然氨基酸中对精氨酸和赖氨酸的选择性识别，探究了环芳酰胺双组分凝胶选择性识别精氨酸（或赖氨酸）的机理。本项目进一步完善了氢键介质的寡聚芳酰胺类化合物凝胶体系，为实现下一步的在生物材料方面的应用打下了基础。