由于配位键的可逆性和溶剂化效应,协调自组装途径通常很难在溶液中通过实验阐明,因为中间体和产品处于不断的平衡状态。在这里,我们表明,这些瞬态和高能自组装中间体中的一些可以通过球磨方法获得。其中,FujitaPd6L14笼的高度水性不稳定的Pd3L11和Pd6L14开笼中间体以及MukherjeePd6L24胶囊的Pd2L22,Pd3L21和Pd4L22中间体成功地捕获在固态中,其中L1=2,4,6-三(4-吡啶基)-1,3,5-三嗪且L2=1,3,5-三(1-咪唑基)苯)。它们的结构通过基于溶液的表征工具的组合来分配,例如标准NMR光谱,DOSYNMR,ESI-MS和X射线衍射。总的来说,我们的结果突出了使用机械化学来访问独特的化学空间的机会,与传统的基于溶液的超分子自组装反应相比,具有极大的不同反应性。
Due to the reversible nature of coordination bonds and solvation effect, coordination self-assembly pathways are often difficult to elucidate experimentally in solution, as intermediates and products are in constant equilibration. The present study shows that some of these transient and high-energy self-assembly intermediates can be accessed by means of ball-milling approaches. Among them, highly aqueous-unstable Pd3 L11 and Pd6 L14 open-cage intermediates of the framed Fujita Pd6 L14 cage and Pd2 L22 , Pd3 L21 and Pd4 L22 intermediates of Mukherjee Pd6 L24 capsule are successfully trapped in solid-state, where Pd=tmedaPd2+ , L1=2,4,6-tris(4-pyridyl)-1,3,5-triazine and L2=1,3,5-tris(1-imidazolyl)benzene). Their structures are assigned by a combination of solution-based characterization tools such as standard NMR spectroscopy, DOSY NMR, ESI-MS and X-ray diffraction. Collectively, these results highlight the opportunity of using mechanochemistry to access unique chemical space with vastly different reactivity compared to conventional solution-based supramolecular self-assembly reactions.