Centre for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, S-221 00 Lund, Sweden.
Dalton Trans. 2013 Jun 21;42(23):8484-91. doi: 10.1039/c3dt50190f. Epub 2013 Apr 26.
Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({2,6-bis[(di-t-butylphosphino)methyl]phenyl}palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating, loss of the solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing a strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion, a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition.
理解先进材料组装的机制对于设计具有所需性质的新材料至关重要。在这里，我们报告了一种通过手性 PCN 钯配合物（{2,6-双[(二-叔丁基膦基)甲基]苯基}钯（II）卤化物）构象体自发拆分来形成手性、潜在多孔材料的方法。结晶过程受弱氢键控制，导致手性 qtz-网络和通道结构，如 X = Cl 和 Br 的 16 个此类晶体结构所示，其中包含各种溶剂如戊烷和溴丁烷。钯上的第四个配体（除了手性配体外）起着至关重要的作用；氯化物和溴化物主要形成具有大 1D 通道的六方晶体，而碘化物（大概由于其氢键能力较差）形成无通道的单斜晶体。六方通道完全疏水，充满无序的溶剂分子。加热时，溶剂会失去，六方晶体转变为其他无孔多晶型物。通过引入强酸，也可以将结晶过程导向不同的方向，得到几种不同的无孔多晶型物。总之，可以制定一些规则来预测基于手性钯配合物的六方通道结构的形成。这些规则对于未来具有存储和分子识别应用的自组装材料的合理设计非常重要。
