Conformationally Adaptive Molecular Cages Enabled by Metal Cluster-Mediated Assembly.

Natural macromolecules achieve complexity by accessing multiple conformational states, but replicating such adaptability in synthetic systems remains a central challenge. Here, we present a cluster-mediated conformational assembly (CMCA) strategy for building adaptive molecular cages with stimuli-responsive dynamics. In this approach, two metal clusters, bridged by three flexible arylthioether ligands, 1,2-bis((pyridin-4-ylthio)methyl)benzene (bpmb), yield caged conformational assemblies (CCAs) that exhibit extensive structural diversity. Single-crystal X-ray diffraction resolved 20 conformers among 64 states predicted computationally, with interconversion directed by solvent polarity, halide binding, and guest encapsulation. Encapsulation further enables reversible switching between static and gyroscopic states, while stabilization relies on C-H···π, C-H···S, and cation···π interactions. Density functional theory (DFT) calculations map a near-degenerate energy landscape, underpinning the dynamic behavior. This cluster-based approach establishes a design principle for chemically addressable conformational adaptability, offering opportunities in molecular recognition, responsive materials, and supramolecular regulation.