Liu Fengbo, Kriat Amine, Rosas Roselyne, Bergé-Lefranc David, Gigmes Didier, Pascal Simon, Siri Olivier, Liu Simin, Kermagoret Anthony, Bardelang David
School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan 430081, People's Republic of China.
Aix Marseille Univ, CNRS, ICR, AMUTech, Marseille, France.
Org Biomol Chem. 2023 Dec 6;21(47):9433-9442. doi: 10.1039/d3ob01723k.
Previously, we reported a guest molecule containing a viologen (V), a phenylene (P) and an imidazole (I) fragment (VPI) forming a host : guest 2 : 2 complex with cucurbit[8]uril (CB[8]) and an unprecedented 2 : 3 complex with cucurbit[10]uril (CB[10]). To better address the structural features required to form these complexes, two VPI analogues were designed and synthesized: the first with a tolyl (T) group grafted on the V part (T-VPI) and the second with a naphthalene (N) fused on the imidazole (I) part (VPI-N). While VPI-N afforded a discrete well-defined 2 : 2 complex with CB[8] and a 2 : 3 complex with CB[10], T-VPI organized also as a 2 : 2 complex with CB[8] but no well-defined complex was obtained with CB[10]. These complexes were studied by NMR spectroscopy, notably DOSY, which allowed us to estimate binding constants for 2 : 2 complex formation with CB[8], pointing to more stable 2 : 2 complexes with more hydrophobic guests. UV-vis and fluorescence spectroscopy confirmed complex formation, suggesting host-stabilized charge-transfer interactions. Therefore, the simple addition of CB[8] or CB[10] enabled us to control the level of guest stacking (dimer or trimer) using relevant pairs of synthetic hosts through spontaneous host : guest quaternary or quinary self-assembly.
此前，我们报道了一种含有紫精（V）、亚苯基（P）和咪唑（I）片段的客体分子（VPI），它与葫芦[8]脲（CB[8]）形成了主体∶客体2∶2配合物，并与葫芦[10]脲（CB[10]）形成了前所未有的2∶3配合物。为了更好地研究形成这些配合物所需的结构特征，我们设计并合成了两种VPI类似物：第一种是在V部分接枝了甲苯基（T）基团（T-VPI），第二种是在咪唑（I）部分稠合了萘（N）基团（VPI-N）。虽然VPI-N与CB[8]形成了明确的2∶2配合物，与CB[10]形成了2∶3配合物，但T-VPI也与CB[8]形成了2∶2配合物，然而与CB[10]未得到明确的配合物。通过核磁共振光谱，特别是扩散排序光谱（DOSY）对这些配合物进行了研究，这使我们能够估算与CB[8]形成2∶2配合物的结合常数，表明与疏水性更强的客体形成的2∶2配合物更稳定。紫外-可见光谱和荧光光谱证实了配合物的形成，表明存在主体稳定的电荷转移相互作用。因此，通过自发的主体∶客体四级或五级自组装，简单地添加CB[8]或CB[10]，使我们能够利用相关的合成主体对来控制客体堆积的程度（二聚体或三聚体）。
