Recognition Selectivities of Lasso-Type Pseudo[1]rotaxane Based on a Mono-Ester-Functionalized Pillar[5]arene

• Main Authors: Wen-Xue Zhang, Lu-Zhi Liu, Wen-Gui Duan, Qing-Qing Zhou, Cui-Guang Ma, Yan Huang
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: Molecules
• Subjects: pillar[5]arenes; pseudo[1]rotaxane; host–guest behavior; self-assembly
• Online Access: https://www.mdpi.com/1420-3049/24/15/2693

Two types of mono-ester-functionalized pillar[5]arenes, P1 and P2, bearing different side-chain groups, were synthesized. Their host−guest complexation and self-inclusion properties were studied by ¹H NMR and 2D nuclear overhauser effect spectroscopy (NOESY) NMR measurements. The results showed that the substituents on their phenolic units have a great influence on the self-assembly of both pillar[5]arenes, although they both could form stable pseudo[1]rotaxanes at room temperature. When eight bulky 4-brombutyloxy groups were capped on the cavity, instead of methoxy groups, pseudo[1]rotaxane P1 became less stable and its locked ester group in the inner space of cavity was not as deep as P2, leading to distinctly different host−guest properties between P1 and P2 with 1,6-dibromohexane. Moreover, pillar[5]arene P1 displayed effective molecular recognition toward 1,6-dichlorohexane and 1,2-bromoethane among the guest dihalides. In addition, the self-complex models and stabilities between P1 and P2 were also studied by computational modeling and experimental calculations.