关于可控组装的一些思考(一)--从催化到催组装

Some thoughts about controllable assembly (Ⅰ)——From catalysis to cassemblysis

分子组装的范畴和复杂性远大于合成反应,但是它们有着相同目标,即高选择性和高效率地创造新物质和制备新功能材料.因此,我们尝试将合成中广泛应用的催化概念拓展至组装研究,提出用于调控和加速组装过程的催组装(cassemblysis)的新思路.为此,我们将迄今泛用的自组装、助组装等术语重新进行规范和分类,即所有的分子组装可分为自组装和助组装.绝大多数组装属于助组装,这可进一步分为催组装、共组装和外场助组装3大类.催组装中的催组剂(cassemblyst)类似于合成中的催化剂,可在不改变总吉布斯自由能变化的条件下加速组装过程,催组装因此有望成为在分子以上层次高选择性且高效率地创造新物质的最佳途径.一些催组装体系在组装之后还会进一步进行化学耦联反应,由此显著提高产物的稳定性,组装与耦联总过程可称为催组联(catassemblysis).我们分别在小分子和生物大分子两个层次上,分析说明了迄今已被不自觉使用的催组装和催组联的一些典型事例,提出了光电催组装的设想,比较了与催组装关联的纳米粒子组装体系,探讨了与催组装相关的简要模型和机理.本文强调,在开展可控组装研究中,不仅要设计与合成各种新组装基元,而且要注重构建催组剂和催组联剂,发展催组装的实验和理论方法学,揭示催组剂作用于组装基元的机理,将有望推动可控组装在创造新物质和制备新功能材料方面发挥更大作用.

Molecular assembly processes are in general much more complex than chemical synthesis. Their goal is the same, that to create a variety of new matter and new functional materials. In accordance with their similarities, the concept of catalysis, which is widely used in chemical synthesis, could be extended to assembly. Herein we suggest that the term ＂cassemblysis＂ be used when referring to increased rates and control during assembly. The role played by a cassemblyst in molecular assembly is similar to that played by a catalyst in a synthesis witia high efficiency and selectivity. Furthermore, it may be helpful to classify some terms which are used often but without clarity in the literature, such as self-assembly and assisted self-assembly. Molecular assembly can be divided into two major types, self-assembly and assisted assembly. Most assembly processes belong to assisted assembly, which can be further divided into three categories： cassemblysis, co-assembly and field-assisted assembly. Of these lhree, cassemblysis is the most efficient way to create new materials （e.g., soft matter） above the molecular level. After cassemblysis, some assembly systems undergo a chemical coupling reaction which significantly enhances stability and prevents them from de-assembling. This increased stability is essential for practical applications. We call this cassembly-reaction process ＂catassemblysis＂. We present some typical examples involving small molecules and large biological molecules to show that cassemblysis and catassemblysis are very common, especially in biological systems. We believe that photo-electro-cassemblysis is possible and that the concept of cassembly could be extended to controllable nanoparticle （or other nanostructure） assembly. Finally we discuss the primary mechanism of cassemblysis and catassemblysis. With emphasis on the experimental and theoretical methodologies of cassemblysis, controllable assembly could play a greater role in creating new matter and new functional materials.