Salt effects on the rates of a thiol cyclisation reaction within a yocto-litre inner-space

ABSTRACT The appreciation of the central role of Coulombic interactions in enzyme catalysis has led to the development of many ‘spin-off’ strategies for controlling chemical reactions. In particular, supramolecular chemistry has become increasingly proficient in using encapsulation/compartmentalisation to control both stoichiometric and catalytic reactions within the inner-spaces of hosts. This noted, there are still many open questions around the design of electrostatic potential fields within such hosts, and how exogenous factors can be used to fine-tune these properties. Here, we report on the cyclisation of 12-bromododecane-1-thiol 2 inside supramolecular capsule 1 2 to give thiacyclotridecane 3, and how the rate of this reaction changes as a function of exogenous salts. We find that this cyclisation is slowed in the presence of exogenous anions, with attenuation being highly dependent on both their nature and concentration. Thus, this work demonstrates how anions at the more-weakly solvated end of the Hofmeister series can associate with the outer walls of the capsule and so attenuate cyclisation. This suggests new ways in which reactions in inner-spaces can be indirectly modulated by exogeneous chemical entities. GRAPHICAL ABSTRACT