Ancillary Ligand Engineering Controls Supramolecular Host Architecture
Year: 2026
Type: preprint
Abstract: Ancillary ligands (ALs) in coordination cages are commonly regarded as passive protecting groups whose primary role is to stabilize discrete cages and prevent formation of extended coordination networks. Here, we introduce ancillary ligand engineering (ALE) as a strategy for controlling the topology and dynamics of palladium-based coordination cages without modifying the metal or triimidazoylbenzene panel ligand. Systematic variation of substituents at the AL nitrogen atoms tunes both the rotational freedom of Pd-bound imidazole (Im) groups and the N–Pd–N coordination angle, thereby shifting the equilibrium between constitutional isomers with distinct tube- and capsule-shaped topologies. NMR spectroscopy reveals a gradual progression from a capsule-rich equilibrium with the smallest AL, ethylenediamine, to a strongly tube-biased equilibrium with the bulkiest tetraethylethylenediamine. Kinetic measurements further show that increasing AL bulk alters both intercage isomerization rates and the nature of the isomerization pathway. The capsule–tube equilibrium can be further shifted by guest encapsulation, with planar and tetrahedral guests favoring the tube and capsule hosts, respectively, thereby providing an orthogonal means to control cage architecture. ALE thus provides a simple and generalizable strategy for programming the topology and kinetic stability of coordination cages while leaving the primary cage-building components unchanged.
Source: ChemRxiv
Authors: Promeet K. Saha, Michał J. Białek, Rafal Klajn
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7208774448