Cycling a Tether into Multiple Rings: Pt-Bridged Macrocycles for Differentiated Guest Recognition, Pseudorotaxane Transformations, and Guest Capture and Release

Angew Chem Int Ed Engl. 2023 Jan 23;62(4):e202216029. doi: 10.1002/anie.202216029. Epub 2022 Dec 14.

Abstract

Macrocycle engineering is a key topic in supramolecular chemistry. When synthesizing a ring, one can obtain either complex mixtures of macrocycles of different sizes or a single ring if a template is utilized. Here, we unite these approaches along with post-synthetic modifications to transform a single tether into multiple rings-up to five per tether. The macrocycles contain two bridged phenylpyridine ligands that are connected through a Pt atom, which defines the rings' shape, size, and host activity. All rings undergo redox reactions (between PtII and PtIV ) that allow for large conformational changes. Their reactivity, together with their host performance, is a convenient way to control the capture and release of guests, to mediate ring transformations, and to control pseudorotaxane-to-pseudorotaxane conversions. This novel approach could serve to assemble other libraries of small ring molecules, create cyclic polymers bridged by responsive-at-metal nodes, and produce processable mechanically interlocked molecules.

Keywords: Crown Ethers; Host-Guest Chemistry; Macrocycles; Platinum; Supramolecular Chemistry.