Triplet–Triplet Annihilation-Based Photon Upconversion with a Macrocyclic Parallel Dimer

The integration of multiple chromophore units into a single molecule is expected to improve the performance of photon upconversion based on triplet–triplet annihilation (TTA-UC) that can convert low energy photons to higher energy photons at low excitation intensity. In this study, a macrocyclic parallel dimer of 9,10-diphenylanthracene (DPA) with a precisely parallel orientation, named MPD-2, is synthesized, and its TTA-UC properties are investigated. MPD-2 shows a green-to-blue TTA-UC emission in the presence of a triplet sensitizer, platinum octaethylporphyrin (PtOEP). Compared to monomeric DPA, MPD-2 results in an enhancement of the spin statistical factor of TTA and a decrease in the excitation light intensity due to the intramolecular TTA process. The obtained structure–property relationship provides important information for the further improvement of TTA-UC properties.