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.