Oosterom G. Eric, Reek Joost N. H., Kamer Paul C. J., van Leeuwen Piet W. N. M.
Institute of Molecular Chemistry University of Amsterdam Nieuwe Achtergracht 166, 1018 WV Amsterdam (The Netherlands).
Angew Chem Int Ed Engl. 2001 May 18;40(10):1828-1849.
Dendrimers are well-defined hyperbranched macromolecules with characteristic globular structures for the larger systems. These novel polymers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them. The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers, resulting in a rapid development of dendrimer chemistry. The position of the catalytic site(s) as well as the spatial separation of the catalysts appears to be of crucial importance. Dendrimers that are functionalized with transition metals in the core potentially can mimic the properties of enzymes, their efficient natural counterparts, whereas the surface-functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis. This might yield superior catalysts with novel properties, that is, special reactivity or stability. Both the core and periphery strategies lead to catalysts that are sufficiently larger than most substrates and products, thus separation by modern membrane separation techniques can be applied. These novel homogeneous catalysts can be used in continuous membrane reactors, which will have major advantages particularly for reactions that benefit from low substrate concentrations or suffer from side reactions of the product. Here we review the recent progress and breakthroughs made with these promising novel transition metal functionalized dendrimers that are used as catalysts, and we will discuss the architectural concepts that have been applied.
树枝状大分子是定义明确的超支化大分子，对于较大的体系具有特征性的球状结构。这些新型聚合物激发了许多化学家去开发新材料，并且已经探索了多种应用，催化就是其中之一。近年来合成方法取得的显著进展提高了功能化树枝状大分子的可及性，导致树枝状大分子化学迅速发展。催化位点的位置以及催化剂的空间分离似乎至关重要。核心用过渡金属功能化的树枝状大分子有可能模拟酶（它们高效的天然对应物）的性质，而表面功能化体系则被认为可以填补均相催化和多相催化之间的空白。这可能会产生具有新性质（即特殊反应性或稳定性）的优异催化剂。核心和外围策略都能得到比大多数底物和产物大得多的催化剂，因此可以应用现代膜分离技术进行分离。这些新型均相催化剂可用于连续膜反应器，这对于那些受益于低底物浓度或受产物副反应影响的反应尤其具有主要优势。在此，我们综述了这些用作催化剂的有前景的新型过渡金属功能化树枝状大分子的最新进展和突破，并将讨论所应用的结构概念。
