Streamlined synthesis of meta- or para-substituted triphenylamine[3]arenes and their hierarchical assembly into polyhedral cages

Abstract

Triphenylamine[3]arenes (TPA[3]s) are a novel class of macrocyclic scaffolds with remarkable potential in supramolecular chemistry. In this study, we present a streamlined synthesis of TPA[3]s featuring meta- or para-substituted bromophenyl or ester moieties on the nitrogen-bridging units via a BF₃·Et₂O-catalysed one-pot Friedel–Crafts reaction, achieving up to near-quantitative yields within five minutes. These labile substituents at the equatorial positions enable efficient post-cyclisation functionalisation under mild conditions, facilitating the introduction of diverse functional groups, including nitrophenyl, pyrene, terpyridine, and carboxylic acid units. These meta-functionalised TPA[3]s exhibit exceptional structural flexibility, enabling their use as tri-topic building blocks for the construction of metal–organic cages (MOCs) through a subcomponent self-assembly strategy. By precisely tuning ligand denticity and metal coordination, we synthesised a diverse range of MOCs, including tetrahedral M₄L₄ cages, dimeric M₃L₂ assemblies, and octahedral M₆L₄ architectures. These results demonstrate the versatility of TPA[3] scaffolds in advancing hierarchical supramolecular assembly and highlight their potential for creating structurally diverse and well-defined supramolecular architectures.