The Length of Molecular Tethers Can Be Used to Control the Structure and Electronic Properties of Stapled Supramolecular Polymers

Formed through equilibrium-driven processes, π-conjugated supramolecular polymers (π-SPs) are equipped with electronic structures that are primarily governed by van der Waals interactions between repeating units. Consequently, the structure–function relationships of these materials are extremely sensitive to changes in temperature, solvent composition, and building block concentration. These experimental constraints not only render the processing of π-SPs challenging but also restrain the molecular toolkit to tailor, by design, their ground, and excited-state electronic structures without completely overhauling the structural design of their repeating units. Herein, we show that stapling initially formed π-SPs with a short molecular tether delivers electronically and structurally robust nanoscale objects whose ground-state electronic structures are insensitive to changes in temperature, thus making the tethering component a versatile synthetic handle to tailor the functions of π-SPs post assembly. Ultrafast transient absorption measurements that track the excited-state dynamics of stapled structures further highlight their structural rigidity. Photoexcitation of the stapled π-SPs generates excited states with mixed Frenkel exciton and charge-transfer character. Notably, we find that the charge-transfer contributions to these states can be enhanced by increasing the structural rigidity of the π-SPs, providing a potential pathway for separating charges for light-harvesting applications. Deviating from conventional supramolecular tools, our reported post-assembly modification strategy highlights a new set of design principles that can guide the molecular engineering of materials with designer electronic properties for applications in light-harvesting, photocatalysis, and organic electronics.