Flexible covalent organic pillars ( flex-COP-n ) are adaptive nanotubular hosts formed via dynamic imine condensation. Their self-assembly displays an odd–even effect, yielding enantiomeric or meso duplexes. Host–guest studies reveal binding modes shaped by mutual deformation and geometric complementarity, underscoring their capacity for responsive molecular recognition.

Abstract

Flexible covalent organic pillars ( flex-COP-n ) are introduced as a family of dual-open-ended nanotubular hosts constructed via dynamic imine condensation between pillararene-derived macrocyclic building blocks and conformationally mobile ─(CH₂) _n ─ aliphatic linkers. These discrete molecular containers feature well-defined tubular channels capable of adaptive host–guest interactions. The self-assembly process exhibits a pronounced odd–even effect, yielding either enantiomeric or meso duplexes through distinct chiral self-sorting pathways. Host–guest interactions between flex-COP-4 and a series of α,ω-dibromoalkanes were systematically investigated using NMR spectroscopy and single-crystal X-ray crystallography. The resulting inclusion complexes span a continuum of binding modes—from relaxed encapsulation to strained, overpacked assemblies—governed by geometric complementarity and mutual host–guest deformation. These findings highlight the role of conformational flexibility in modulating molecular recognition under nanoscale confinement and establish flex-COP-n as a dynamic platform for mimicking adaptive features of biological receptors.