Heavy main-group elements in supramolecular chemistry and nonlinear optical materials

我们能把化学自组装推进多远？这是《科学》杂志为纪念创刊125周年（第309卷，第5731期，2005年7月1日，第95页）所强调的当前25个“大问题”之一。在过去的30年里，科学家们在利用分子之间的相互作用来构建越来越复杂的超分子结构方面取得了惊人的进展。这种方法通常受到大自然的启发：氢键（存在于液态水和DNA中）和金属离子的配位（在血红蛋白的活性部位观察到）是最常用的力量，可以将小的构建块自发组织成大的、复杂的、有时是功能性的结构。在垂直方向上，目标是建立更大的分层结构。在水平方向上，目的是扩展自组装范式，以利用其他交互。环（聚集碳纳米管的“胶”）和“范德华力”（蜡在环境条件下是固体的原因）的“pi堆叠”的使用现在已经有了很好的记录。其他的分子间作用力之所以没有被应用，主要是因为到目前为止，人们对它们的理解还很有限，比如重p块元素（元素周期表右下方的元素）所产生的原子间接触。对这一现象的一连串命名与我们理解的演变相似：最初的“非键接触”变成了“弱键相互作用”，现在的术语“次级键相互作用”（简称SBI）越来越被人们所接受。本申请为一项研究项目寻求资金支持，该项目旨在研究重p块元素的sbi在超分子化学和分子自组装中的应用。sbi具有独特的特性，可以用来控制自组装材料的性能。例如，虽然氢键是电子迁移的障碍，但sbi增强了电导率。此外，sbi还能稳定含有特殊成分的化合物。一个相关的研究方向涉及重主族元素化合物的先进光学特性，这种特性将允许以光脉冲的形式传输和处理大量信息。

How far can we push chemical self-assembly? This is one of the 25 current "Big Questions" highlighted by the journal Science to mark its 125th anniversary (vol. 309, No. 5731, 1 July 2005, p. 95). During the last 30 years scientists have made astonishing progress in using the interactions between molecules to construct supramolecular structures with increasing complexity. This approach is often inspired by nature: hydrogen bonds (present in liquid water and DNA) and the coordination of metal ions (as observed in the active site of haemoglobin) have been the most-commonly used forces to drive the spontaneous organisation of small building blocks into large, complex, and sometimes functional structures. In a vertical direction, the goal is to build bigger and hierarchical structures. In the horizontal, the intention is to expand the self-assembly paradigm to take advantage of other interactions. The use of "pi-stacking" of rings (the "glue" that agglomerates carbon nanotubes) and "van der Waals forces" (the reason wax is solid under ambient conditions) is now well documented. Other intermolecular forces have not been used mostly because they have been poorly understood until now, as is the case for the inter-atomic contacts made by the heavy p-block elements (those on the lower right hand side of the periodic table). The succession of names given to this phenomenon parallels the evolution of our understanding: the initial "non-bonded contact", became "weakly bonding interaction" and now the term "secondary bonding interaction" (abbreviated SBI) is gaining increasing acceptance. This application seeks funding for a research program that pursues the use of SBIs of heavy p-block elements in supramolecular chemistry and molecular self-assembly. SBIs have distinctive features that can be exploited to control the properties of self-assembled materials. For example, while hydrogen bonds are barriers to electron mobility, SBIs enhance conductivity. In addition, SBIs can stabilise compounds with unusual compositions. A related line of research is concerned with advanced optical properties of compounds of heavy main-group elements that will permit transmission and processing of large amounts of information as light pulses.