Triplet–Triplet\nAnnihilation-Based Photon Upconversion\nwith a Macrocyclic Parallel Dimer

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