Exo-templating via pseudorotaxane formation reduces pathway complexity in the multicomponent self-assembly of M12L24 nanospheres

Abstract

Selective formation of multicomponent structures via the self-assembly of numerous building blocks is ubiquitous in biological systems but challenging to emulate synthetically. More components introduce additional possibilities for kinetic intermediates with trap-state ability, hampering access to desired products. In covalent chemistry, templates, reagents and catalysts are applied to create alternative pathways for desired product formation. Analogously, we enlist exo-templating to mould the formation of large, multicomponent supramolecular structures. Specifically, a charged ring docks at 1,5-dioxynaphthalene stations within exo-functionalized building blocks to promote formation of cuboctahedral Pd₁₂L₂₄ nanospheres via exoskeletal templating. With the exo-templating ring present, nanosphere formation occurs via small Pd_x–L_y oligomers, while in the absence of the ring a Pd_x–L_y polymer resting state rapidly evolves, from which nanosphere formation occurs slowly. We demonstrate a form of kinetic templating—via intermediate destabilization—resembling properties observed in catalysis. Importantly, unlike typically employed endo-templates, we demonstrate that exo-templating is particularly suited for larger, complex, self-assembled structures.