Nonconventional Three-Component Hierarchical Host–Guest Assembly Based on Mo-Blue Ring-Shaped Giant Anion, γ‑Cyclodextrin, and Dawson-type Polyoxometalate

In
this communication, we report on a noteworthy hybrid supramolecular
assembly built from three functional components hierarchically organized
through noncovalent interactions. The one-pot synthesis procedure
leads to the formation of large Mo-blue ring-shaped anion {Mo154}, which contains the supramolecular adduct based on the
symmetric encapsulation of the Dawson-type [P2W18O62]6– anion by two γ-cyclodextrin
units. Such a nanoscopic onion-like structure, noted [P2W18O62]@2γ-CD@{Mo154} has
been characterized by single-crystal X-ray diffraction, thus demonstrating
the capability of the giant inorganic torus to develop relevant supramolecular
chemistry, probing the strong affinity of the inner and outer faces
of the γ-CD for the polyoxometalate surfaces. Furthermore, interactions
and behavior in solution have been studied by multinuclear NMR spectroscopy,
which supports specific interactions between γ-CD and POM units.
Finally, the formation of this three-component hybrid assembly from
one-pot procedure, in water and using nearly stoichiometric conditions,
is discussed in terms of the driving forces orchestrating this highly
efficient multilevel recognition process.

本研究报道了一种极具研究价值的杂化超分子组装体（supramolecular assembly），该组装体由三种功能组分通过非共价相互作用（noncovalent interactions）进行层级组装构建而成。采用一锅法合成（one-pot synthesis）工艺可得到大尺寸钼蓝环状阴离子{Mo154}，其内部包含由两个γ-环糊精（γ-cyclodextrin）单元对称包封道森型（Dawson-type）[P2W18O62]6–阴离子所形成的超分子加合物（supramolecular adduct）。该被标记为[P2W18O62]@2γ-CD@{Mo154}的纳米级洋葱状结构，已通过单晶X射线衍射（single-crystal X-ray diffraction）完成表征，从而证实了巨型无机环面（giant inorganic torus）能够开展具有研究价值的超分子化学研究，并揭示了γ-环糊精的内外表面对多金属氧酸盐（polyoxometalate，POM）表面具有强亲和性。此外，通过多核核磁共振波谱法（multinuclear NMR spectroscopy）对其在溶液中的相互作用与行为进行了研究，结果证实了γ-环糊精与POM单元之间存在特异性相互作用。最后，本文还讨论了该三组分杂化组装体在水溶液中采用近化学计量比条件（stoichiometric conditions）下的一锅法合成过程，并剖析了调控这一高效多级识别过程的驱动力（driving forces）。