Using the Mechanical Bond to Tune the Performance of a Thermally Activated Delayed Fluorescence Emitter**

We report the characterization of rotaxanes based on a carbazole-benzophenone thermally activated delayed fluorescence luminophore. We find that the mechanical bond leads to an improvement in key photophysical properties of the emitter, notably an increase in photoluminescence quantum yield and a decrease in the energy difference between singlet and triplet states, as well as fine tuning of the emission wavelength, a feat that is difficult to achieve when using covalently bound substituents. Computational simulations, supported by X-ray crystallography, suggest that this tuning of properties occurs due to weak interactions between the axle and the macrocycle that are enforced by the mechanical bond. This work highlights the benefits of using the mechanical bond to refine existing luminophores, providing a new avenue for emitter optimization that can ultimately increase the performance of these molecules.

Automated summary

This study characterizes rotaxanes based on a carbazole-benzophenone thermally activated delayed fluorescence luminophore, demonstrating that the mechanical bond can lead to an improvement in key photophysical properties of the emitter. Computational simulations and X-ray crystallography suggest that weak interactions enforced by the mechanical bond between the axle and macrocycle result in the tuning of properties. The use of mechanical bonds to refine existing luminophores provides a new avenue for emitter optimization, ultimately increasing the performance of these molecules.