DESIGN AND FUNCTION OF THE SELF-ASSEMBLED NANO-RINGS

为了将Ag^+与柔性芳香胺配体结合，构建纳米尺寸的多边形或多面体，我们决定使用N， N'-双（4-吡啶基）苄胺(1)。用MMFF对1进行构象分析后的B3LYP/3- 21g计算表明，最稳定的构象的N_<(1)>-N_<(2)>-N_<(3)>角约为109.7°，这与配体1的x射线结构完全相同。为了研究溶液中Ag +与1的化学计量关系，进行了Ag +诱导的1H-NMR和UV-VIS滴定实验。两种滴定结果都表明配体1在溶液中与Ag^+离子形成（1:1）_n络合物。在N_2气氛中，将等量的配体1与AgOTf在CH_3CN和CH_3OH中混合，得到固体1-AgOTf配合物。两天后定量地析出单晶。以间硝基苄基醇为溶剂，采用FAB-MS研究了配合物中配体1与Ag +离子的化学计量。FAB-MS还表明，配合物中配体1与Ag^+之间的化学计量比为（1:1）_n。在90K下测量了1-AgOTf配合物的x射线晶体学。该络合物是包含6个OTf离子的离散环六聚体（1:Ag^+ = 6:6），六聚体呈六边形。在建筑群的中心有一个大洞。由于腔内原子的无序性，在90K时腔内溶剂原子没有被指定。空腔直径约为20Å (Ag-Ag距离：21.2Å， N_<（2)>-N_<（2’）>距离：21.7Å）。有趣的是，这个六边形并不是平面的，而是一个椅状构象，有点像环己烷的椅状构象。N_<(2)>原子位于椅子结构的角上。配合物中的N_<(1)>-N_<(2)>-N_<(3)>键角和N_<(1)>-Ag-N_<(3)>键角分别为109.7°和170°。中心的纳米椅子与一侧的6个纳米椅子重叠，两侧的纳米椅子共12个。这些纳米椅子相互堆叠，形成蜂窝状的空腔。参与重叠位置的原子用球棍模型表示。有两种面对面的π-π堆积（吡啶-吡啶堆积：黄-蓝，苯-苯堆积：黄-红）位点。碳-碳距离和Ag^+-Ag^+距离分别为3.26 ~ 3.67和3.41Å。这些碳-碳和Ag^+-Ag^+的距离与前面描述的无限网络系统中观察到的距离相当。在这个络合物中，没有观察到Ag^+-p相互作用。Stang等报道，在使用Pd^<2+>和Pt^<2+>离子的自组装体系中，具有109.5°角的角双齿配体需要具有120°角的角双齿配体，形成五边形、三角形双锥体、金刚烷或立方面体，以及六边形大环体系。少

In order to construct the nano-sized polygons or polyhedra by the combination of Ag^+ and flexible aromatic amine ligands, we decided to use N, N'-bis(4-pyridyl)benzylamine (1). B3LYP/3-21G calculations after the conformation analysis by MMFF of 1 showed that the N_<(1)>-N_<(2)>-N_<(3)> angle of the most stable conformer is about 109.7°, which is exactly the same as that of X-ray structure of ligand 1. The Ag^+ induced ^1H-NMR and UV-VIS titration experiments were carried out in order to investigate the stoichiometry between Ag^+ and 1 in solution. Both titration results suggest that ligand 1 forms a (1:1)_n complex with Ag^+ ion in solution. A solid 1-AgOTf complex was obtained by mixing equimolar amount of ligand 1 in CH_3CN and AgOTf in CH_3OH in an N_2 atmosphere. After two days, single crystals precipitated quantitatively. The stoichiometry between ligand 1 and Ag^+ ion in the complex was studied by FAB-MS using m-nitrobenzyl alcohol. The FAB-MS also suggests that the stoichiometr … More y between ligand 1 and Ag^+ in the complex is (1:1)_n. The X-ray crystallography of 1-AgOTf complex was measured at 90K. The complex is a discrete cyclic hexamer (1:Ag^+ = 6:6) including six OTf ions and the hexamer is in the form of a hexagon. There is a large cavity in the center of the complex. Because of the disorder of atoms in the cavity, the solvent atoms in the cavity were not specified at 90K. The diameter of the cavity is about 20Å (Ag-Ag distance: 21.2Å and N_<(2)>-N_<(2')> distance: 21.7Å). Interestingly, the hexagon is not planer, but forms a chair conformation somewhat like the chair-form of cyclohexane. The N_<(2)> atoms are at the corners of the chair structure. The N_<(1)>-N_<(2)>-N_<(3)> and the N_<(1)>-Ag-N_<(3')> bond angles in the complex are 109.7° and 170°, respectively. A nano chair at the center overlaps with six nano chairs from one side, and a total twelve nano chairs from both sides. The nano chairs stack on each other and make honeycomb-like cavities. The atoms that participate overlapped sites are shown by ball-and-stick models. There are two kinds of face-to-face π-π stacking (pyridine-pyridine stacking: yellow-blue, benzene-benzene stacking: yellow-red) sites. The carbon-carbon distances and Ag^+-Ag^+ distances are 3.26-3.67 and 3.41Å, respectively. These carbon-carbon and Ag^+-Ag^+ distances are comparable to those observed in the infinite network systems described previously. In this complex, Ag^+-p interactions were not observed. Stang et al. reported that the angular bidentate ligands having 109.5° angles form pentagon, trigonal bipyramide, adamantanoid or cuboctahedron in self-assembly systems using Pd^<2+> and Pt^<2+> ions, and hexagonal macrocyclic systems need angular bidentate ligands having 120° angles. Less