Polydentate Lewis acids with oriented acceptor functions

量身定做的分子物质结构允许实现特定的化学反应。自然界以多种方式展示了反应功能的协调空间位置如何导致特定的反应活性(通常是施主功能或氢桥)。这也经常用于合成和构建催化剂和受体。与本文中使用的给体函数(配体设计)相比，具有确定的受体功能(Lewis酸)的放置和取向的例子仍然很少。然而，这样的概念将使我们能够识别阴离子和Lewis碱，从而允许改变它们的性质和反应性。因此，该项目的目的是以明确和定向的方式在合适的分子支架上放置多个Lewis酸功能，以优化Lewis碱性底物的结合。到目前为止，挑战在于用于连接这些功能的合适的分子支架的可及性非常有限。它们必须不含刘易斯碱性单元；否则它们将与底物竞争酸性功能。在第一个项目期间，我们已经开发了基于碳氢化合物或有机硅烷支架分子的刚性主链分子的有效途径。这些化合物包括1，8-官能化的菲，具有四个协调取向功能的光化学可及的菲二聚体，具有可切换选择性的光化学‘二聚化’桥联双(菲)烯，以及具有三个协调取向功能的三苯并三烯。此外，我们还发现了一种非常巧妙的合成方法，该方法合成了一种具有四个炔基指向一个方向的合成蒽二聚体，它的高选择性是二聚化过程中氢桥预络合物的结果。因此，现在很清楚，在众多被测试的系统中，哪些系统为多齿Lewis酸的多步骤合成提供了可行的途径，以便为针对其应用的进一步实验提供大量的数据。我们已经通过几个例子演示了如何将受体函数附加到这些支架上。这些功能是Al、Ga和In元素(也包括锌和汞)的有机金属单元，以及通过D10-D10相互作用结合的电负性取代的硼和硅的非金属功能以及金功能。在第二个项目期，我们打算带来第一个阶段的工作和投资的收获。我们将制备各种新的多齿路易斯酸，并研究它们的化学性质。这些包括分子识别和络合性能的可能性，通过与多齿受体络合来增强Lewis酸的酸性的能力(AIM‘超级Lewis酸’)，通过螯合色散型相互作用产生不寻常的络合物，以及多齿Lewis酸在受挫Lewis对化学中的使用。

Tailor-made structuring of molecular matter allows realizing specific chemical reactivity. Nature demonstrates in manifold ways how concerted spatial placement of reactive functions leads to specific reactivity (usually donor functions or hydrogen bridges). This is also frequently used in synthesis and in the construction of catalysts and receptors. In contrast to the donor functions used in this context (ligand design) examples with defined placement and orientation of acceptor functions (Lewis acids) are still scarce. However, such a concept would enable us to recognize anions and Lewis bases and consequently allow modifying their properties and reactivities. The aim of this project is therefore to place multiple Lewis-acid functions at suitable molecular scaffolds in a defined and oriented way for an optimized binding of Lewis basic substrates. The challenges were so far the very limited accessibility of suitable molecular scaffolds for attaching such functions. They have to be free of Lewis basic units; otherwise they would compete with the substrates for the acidic functions. In the first project period we have developed efficient access to rigid backbone molecules on the basis of hydrocarbons or organosilane scaffold molecules. These include 1,8-functionalized anthracenes, photochemically accessible anthracene dimers with four concordantly oriented functions, photochemically ‘dimerizable’ bridged bis(anthracenes) with switchable selectivities as well as triptycene with three concordantly oriented functions. In addition we found a very elegant synthesis of a syn-anthracen dimer with four alkyne functions pointing into one direction, whose high selectivity is the result of a hydrogen-bridged pre-complex during dimerization. Consequently, it is now clear which of the numerous tested systems provide practicable pathways for the multi-step syntheses to multidentate Lewis-acids, in order to give access to substantial amounts for further experiments aiming at their applications. We have demonstrated for several examples how to attach acceptor functions to these scaffolds. These functions are organometallic units of the elements Al, Ga and In (also Zn and Hg) and electronegatively substituted non-metallic functions of boron and silicon as well as gold functions binding via d10-d10 interactions. In the second project period we intend to bring in the harvest of the work and investment of the first period. We will prepare a variety of new multidentate Lewis-acids and study their chemical properties. These include possibilities of molecular recognition and complexing properties, the ability to enhance the acidity of Lewis acids by complexation with multidentate acceptors (aim ‘super Lewis-acids’), the generation of unusual complexes by chelating dispersive-type interactions, and the use of multidentate Lewis-acids in frustrated Lewis-pair chemistry.