A double-walled hexagonal supermolecule assembled by guest binding
A double-walled hexagonal supermolecule assembled by guest binding
复制标题
DOI：
10.1021/ja005695i
复制
发表时间：
2001-02-14
影响因子：
15
通讯作者：
Jeong, KS
中科院分区：
文献类型：
--
作者：
Cho, YL;Uh, HS;Jeong, KS
由于其强度和方向性，过渡金属-配体相互作用已成为构建各种复杂超分子（如大环1,2和笼1,3）的最有力工具之一。我们最近描述了离散的单核和双核大环可以由四氧化锇、烯烃和双吡啶配体的混合物自发组装。在这个装配母题中，八面体配位中心在装配过程中就地生成，不像大多数其他系统需要额外的步骤来制备具有所需几何形状和性能的金属中心。此外，大环是电中性的，因此基于氢键的分子识别可以在没有其他存在的反离子干扰的情况下进行研究。本文报道了在萘- 2,6 -二醇存在下，由酯基大环自发重组形成的双壁六核六方体的第一个例子。5的四氧化锇(0.1∼1枚,甲苯)的甲苯溶液1:1关于环和5,6-dibutyl-5-decene6导致棕色沉淀在几分钟内室温(方案1)。7强大的红外产品的乐队出现在830 cm - 1、诊断反式OdOsdO债券的八面体dioxoosmate酯之间复杂的结果反应四氧化锇和烯烃和伴随的协调两个吡啶基根cis的关系。8 1h NMR谱显示产物的r -和吡啶基质子分别在8.95和7.66 ppm处有两组双联态，它们都相对于自由配体向下移动（Δδ） 0.1-0.2 ppm)。元素分析，以及1H NMR积分，9揭示了1:1:1的三组分的化学计量；OsO4，联吡啶和5,6 -二丁基-5-癸烯。所有这些数据都与渗透酯产物的对称环状结构一致，例如1。蒸汽压渗透法（VPO）测定了该大环产物在CHCl3中在313 k下的大小，VPO测定的分子量取决于样品的浓度。随着浓度从8 g/kg（溶质/溶剂）增加到27 g/kg，以苄基为标准，分子量从2200逐渐增加到3200（平方1为2651）。如果产物以各种环酯（COEs）的平衡混合物存在，就可以解释这种分子量的浓度依赖性，这让人想起一个动态组合文库。在较低浓度下，较小的大环的相对数量增加，而在较高浓度下，较大的大环或聚集体增加。从1H NMR研究中获得了溶液中COEs平衡混合物的更多证据：(a) r和联吡啶质子的化学位移与浓度有轻微的相关性（Δδ在0.5-50 mM浓度下0.06-0.08 ppm）， (b) r和联吡啶质子的信号在0℃以下分裂成更多的双偶态，可能是由于核磁共振时间尺度上环酯之间的缓慢相互转化（支持信息）。
The transition metal-ligand interaction has been one of the most powerful tools to construct various sophisticated supermolecules such as macrocycles1, 2 and cages, 1, 3 owing to its strength and directionality. We recently described that discrete mono-and dinuclear macrocycles could be spontaneously assembled from a mixture of osmium tetroxide, olefin, and bispyridyl ligand. 4 In this assembling motif, the octahedral coordination center is generated in situ during the assembly process, unlike most other systems which require extra steps for the preparation of the metal center with the desired geometry and properties. Furthermore, the macrocycles are electrically neutral so that molecular recognition based on hydrogen bonds can be studied without interference by otherwise existing counterions. Herein we report the first example of double-walled hexanuclear hexagon formed by spontaneous reorganization of osmate ester-based macrocycles in the presence of naphthalene-2, 6-diol. 5 Addition of osmium tetroxide (∼ 1 equiv, 0.1 M in toluene) to a toluene solution of 1: 1 bipyridine and 5, 6-dibutyl-5-decene6 resulted in brown precipitates within a few minutes at room temperature (Scheme 1). 7 A strong infrared band of the product appeared at 830 cm-1, diagnostic of the trans OdOsdO bond of the octahedral dioxoosmate ester complex which results from the reaction between osmium tetroxide and olefin and concomitant coordination of two pyridyl moieties in a cis relationship. 8 The1H NMR spectrum showed two sets of doublets at 8.95 and 7.66 ppm corresponding to the R-and-pyridyl protons of the product, respectively, both of which were shifted downfield (Δδ) 0.1-0.2 ppm) relative to the free ligand. Elemental analysis, along with 1H NMR integration, 9 revealed a 1: 1: 1 stoichiometry of three components; OsO4, bipyridine and 5, 6-dibutyl-5-decene. All of these data are consistent with the symmetrical cyclic structure, for example 1, of the osmate ester product. Vapor pressure osmometry (VPO) was used to determine the size of this macrocyclic product in CHCl3 at 313 K. 10, 11 The molecular weights measured by VPO (Supporting Information) depend on the concentration of the sample. As the concentration increases from 8 to 27 g/kg (solute/solvent), the molecular weights were gradually increased from 2200 to 3200 (2651 for square 1), using benzil as the standard. This concentration dependence of the molecular weight may be explained if the product exists as an equilibrium mixture of various cyclic osmate esters (COEs), reminiscent of a dynamic combinatorial library. 12 At lower concentrations the relative population of smaller macrocycles is increased, while at higher concentrations larger macrocycles or aggregates increase. 13 More evidences for an equilibrium mixture of COEs in solution were obtained from 1H NMR studies:(a) chemical shifts of the R-and-bipyridyl protons are slightly concentration-dependent (Δδ 0.06-0.08 ppm over concentrations 0.5-50 mM), and (b) signals for R-and-bipyridyl protons split into more sets of doublets below 0 C, possibly due to a slow interconversion between cyclic osmate esters on the NMR time scale (Supporting Information).