A Novel A2L3-Type Triplet-Stranded Helicate Constructed by Subcomponent Self-Assembly Based on Anion Coordination

Abstract

Self-assembly of discrete helical structures using artificial molecules has long attracted considerable attention in supramolecular chemistry. Nevertheless, the studies of anion-templated subcomponent self-assembly for constructing supramolecular helical architectures in a one-pot fashion are scarcely reported. In this study, a novel and discrete A2L3-type (A = anion, L = ligand) triplet-stranded helicate, 1, was efficiently fabricated by anion-templated subcomponent self-assembly (ATSSA) from a PO43−anion, monotopic aniline L0 with a bisurea moiety, and terephthalaldehyde in a one-pot fashion. Additionally, the triple helicate 1 was also able to be constructed by anion coordination-driven assembly (ACDA) from PO43− with Schiff-base ligand L1 formed by imine condensation. The self-assembly of triplet-stranded helicate 1 was elucidated by single-crystal X-ray diffraction (SCXRD) analysis, and experimental spectroscopic data including 1H NMR and high-resolution ESI-MS confirmed the supramolecular helical configuration. Interestingly, upon introducing 4-tert-butyl-2,6-diformylphenol into the initial subcomponent self-assembly system of helix 1, the other fluorescent A2L3-type triplet-stranded helicate, 2, was also capable of being generated in situ through replacing terephthalaldehyde. Furthermore, the discrete helix 2 exhibited reversible disassembly and reassembly behaviors triggered by external acid-base stimuli. This work is expected to offer new insights and rational design strategies for fabricating anion-directed supramolecular helical architectures and may also lay a promising foundation for the construction of supramolecular smart materials.