“Bis-Clamp-Cavity Synergy”, an Efficient Approach to Improve Guest Binding Properties of Macrocyclic Host and Its Application on Detection of Al3+ and Arg in Living Cells

Improving the selective and sensitive binding properties of macrocyclic hosts to target guests is always an interesting challenge. Herein, we introduce a novel "bis-clamp-cavity synergy" strategy to enhance the selectivity and binding sensitivity of pillararenes toward target guests. To achieve this goal, we designed and synthesized A,A'-bis-hydroxynaphthoylhydrazone-functionalized conjugated pillar[5]arene (HGP5), in which bis-hydroxynaphthoylhydrazone plays the role of clamps, while the pillar[5]arene provides the macrocyclic cavity. The bis-clamps and macrocyclic cavity could supply synergistic binding for target guests through multicoordination interactions, multihydrogen bonds, C-H···π and cation···π interactions, and so on. Furthermore, the introduction of the conjugated pillar[5]arene can enhance the signal transmission ability, thereby improving the sensitivity for guest recognition. Benefiting from the bis-clamp-cavity synergy, HGP5 exhibits efficient selective recognition for Arg and Al³⁺. It achieves colorimetric and fluorescent dual-channel recognition for Arg (with the LOD of 2.99 × 10^-8 M) and ultrasensitive recognition of Al³⁺ (with the LOD of 7.94 × 10^-9 M). This strategy can be effectively applied to detect Arg and Al³⁺ in aqueous solution and live cells.