Harnessing remote weak interactions for fine-tuning the catalytic activity of rotaxane-superbases
Year: 2026
Type: preprint
Abstract: Mechanically interlocked molecules offer a distinct strategy for controlling molecular function by translating subtle differences in noncovalent interactions into changes in molecular conformation and reactivity. Here, we show that remote weak interactions can be harnessed to fine-tune the basicity and catalytic activity of mechanically interlocked secondary amines. To this end, we synthesized two bistable rotaxanes, featuring a primary ammonium/amine binding site and either a triazole or a methyltriazolium unit as the secondary binding site. In the base-catalysed Michael addition of malononitrile to beta-nitrostyrene, both deprotonated amine-rotaxanes exhibit substantially higher catalytic activity than both the corresponding non-interlocked thread and the benchmark organobase proton sponge, demonstrating that the mechanical bond can enhance the reactivity of the embedded amine. Importantly, the triazole based-rotaxane shows a twofold higher catalytic activity than that of the triazolium-rotaxane, although the secondary amine as the catalytically active unit is structurally unchanged. Thus, the increased reactivity is caused by the difference in weak noncovalent interactions at the secondary binding site: Weaker binding to the triazole translates into higher basicity of the secondary amine, which in turn increases the catalytic activity of the rotaxane. Collectively, these results demonstrate that weak, remote interactions transmitted through a mechanical bond can modulate the proton-accepting ability and catalytic performance of an interlocked amine, establishing remote co-conformational control of basicity as a design principle for fine-tuning the reactivity of rotaxane superbases.
Source: ChemRxiv
Institution: University of Duisburg-Essen
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221727067