Unimolecular Doublet-Triplet Annihilation Upconversion in Iron(III) Coordination Compounds.

carbene, and a blue fluorescent singlet state on the perylene. By varying the number of attached perylene units from 1 to 4 we gain mechanistic insight and identify the operating regime of unimolecular upconversion that functions not only in fluid solution but also in polymers at room temperature and in frozen glasses at 77 K. Beyond providing a design strategy for diffusion-independent future upconversion architectures, this work establishes unimolecular doublet-triplet annihilation as a fundamentally distinct upconversion concept with strategic advantages over conventional approaches.