Abstract
Formed through equilibrium-driven processes, pi-conjugated supramolecular polymers (pi-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 pi-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 N-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 pi-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 pi-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 pi-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.
