纳米管超分子聚合中的途径复杂性：具有平面手性单体的金属有机纳米管,Journal of the American Chemical Society

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纳米管超分子聚合中的途径复杂性：具有平面手性单体的金属有机纳米管
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-06-12 , DOI: 10.1021/jacs.3c03385
Yingluo Zhao _{1,

2} , Hiroko Kawano ₁ , Hiroshi Yamagishi ₃ , Saya Otake ₁ , Yoshimitsu Itoh ₁ , Hubiao Huang ₂ , E W Meijer ₄ , Takuzo Aida _{1,

2}

Affiliation

在这里，我们报告了手性单体超分子聚合中的异常途径复杂性，它表现出不寻常的手性光学特征，不遵循任何已知的立体化学规则，例如“手性自排序”和“多数规则”。我们新开发了一种平面手性二茂铁为核的四位吡啶基单体FcL，它经过AgBF ₄介导的超分子聚合得到由金属有机纳米环FcNR组成的纳米管FcNT。尽管由于强大的几何限制， FcNR必须是纯手性的，但FcNR甚至可以由外消旋FcL和 AgBF ₄有效地形成。详细研究揭示了产生作为FcNT组成部分的同手性FcNR 的两种竞争途径：(i) 最初形成的无环聚合物 -[ FcL -Ag ⁺ ] _n - 的自发环化和 (ii) 模板 ( FcNR ) 辅助通过Ag ⁺ ··Ag ⁺亲金属相互作用进行环化。两条途径的主导地位根据手性FcL的% ee变化。即，当FcL的% ee高时，-[ FcL -Ag ⁺ ] _n- 必须包含足够长的纯手性序列，可以轻松环化为FcNR。同时，当FcL的% ee较低时，-[ FcL -Ag ⁺ ] _n -中的纯手性序列一定很短，因此几乎不适合自发环化。为什么会形成FcNR？尽管概率非常低，但可以统计生成纯手性-[ FcL -Ag ⁺ ] _n - 并进行自发环化以精细地给出FcNR。我们发现FcNR可以通过使用亲金属相互作用异手性模板化它们自己的合成来扩增。由于这种立体化学偏好，只有当⁽^R,R⁾FcL和⁽^S,S⁾FcL都存在于聚合体系中时， FcNR通过模板辅助机制生长成FcNT才会发生。

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Pathway Complexity in Nanotubular Supramolecular Polymerization: Metal–Organic Nanotubes with a Planar-Chiral Monomer

Here, we report an anomalous pathway complexity in the supramolecular polymerization of a chiral monomer, which displays an unusual chiroptical feature that does not follow any of the known stereochemical rules such as “chiral self-sorting” and “majority rule”. We newly developed a planar-chiral ferrocene-cored tetratopic pyridyl monomer FcL, which underwent AgBF₄-mediated supramolecular polymerization to give nanotubes FcNTs composed of metal–organic nanorings FcNRs. Although FcNRs must be homochiral because of a strong geometrical constraint, FcNRs were formed even efficiently from racemic FcL and AgBF₄. Detailed studies revealed the presence of two competing pathways for producing homochiral FcNRs as the constituents of FcNTs: (i) spontaneous cyclization of initially formed acyclic polymers -[FcL-Ag⁺]_n- and (ii) template (FcNR)-assisted cyclization via a Ag⁺···Ag⁺ metallophilic interaction. The dominance of the two pathways changes depending on the %ee of chiral FcL. Namely, when the %ee of FcL is high, -[FcL-Ag⁺]_n- must contain sufficiently long homochiral sequences that can be readily cyclized into FcNRs. Meanwhile, when the %ee of FcL is low, the homochiral sequences in -[FcL-Ag⁺]_n- must be short and therefore are hardly eligible for spontaneous cyclization. Why were FcNRs formed? Even though the probability is very low, homochiral -[FcL-Ag⁺]_n- can be statistically generated and undergo spontaneous cyclization to give FcNRs minutely. We found that FcNRs can be amplified by heterochirally templating their own synthesis using metallophilic interaction. Because of this stereochemical preference, the growth of FcNRs into FcNTs via the template-assisted mechanism occurs only when both ^(R,R)FcL and ^(S,S)FcL are present in the polymerization system.

更新日期：2023-06-12

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