Elongation of Triplet Lifetime Caused by Intramolecular Energy Hopping in Diphenylanthracene Dyads Oriented to Undergo Efficient Triplet-Triplet Annihilation Upconversion†.

Triplet-triplet annihilation (TTA)-assisted photon upconversion (TTA-UC) in three dyads (DPA-Cn-DPA), comprised of two diphenylanthracene (DPA) moieties connected by nonconjugated C1, C2, and C3 linkages (Cn), has been investigated. The performance of these dyads as energy acceptors in the presence of the energy donor platinum octaethylporphyrin are characterized by longer triplet lifetimes (τT) and different TTA rate constants than those of the parent DPA. The larger τT of the linked systems, caused by "intramolecular energy hopping" in the triplet dyad 3DPA*-Cn-DPA, results in a low threshold intensity, a key characteristic of efficient TTA-UC.