Maximizing Nanoscale Downshifting Energy Transfer in a Metallosupramolecular Cr(III)−Er(III) Assembly Poncet, Maxime Besnard, Céline Jiménez Gallego, Juan Ramón Piguet, Claude Pseudo-octahedral CrIIIN6 chromophores hold a unique appeal for low-energy sensitization of NIR lanthanide luminescence due to their exceptionally long-lived spin-flip excited states. This allure persists despite the obstacles and complexities involved in integrating both elements into a metallosupramolecular assembly. In this work, we have designed a structurally optimized heteroleptic CrIII building block capable of binding rare earths. Following a complex-as-ligand synthetic strategy, two heterometallic supramolecular assemblies, in which three peripherical CrIII sensitizers coordinated through a molecular wire to a central ErIII or YIII, have been prepared. Upon excitation of the CrIII spin-flip states, the downshifted Er(4I13/2 → 4I15/2) emission at 1550 nm was induced through intramolecular energy transfer. Time-resolved experiments at room temperature reveal a CrIII → ErIII energy transfer of 62−73% efficiencies with rate constants of about 8.5 × 105 s−1 despite the long donor−acceptor distance (circa 14 Å). This efficient directional intermetallic energy transfer can be rationalized using the Dexter formalism, which is promoted by a rigid linear electronrich alkyne bridge that acts as a molecular wire connecting the CrIII and ErIII ions. 2024-09-04T09:23:27Z 2024-09-04T09:23:27Z 2024-08-20 journal article Maxime Poncet, Céline Besnard, Juan-Ramón Jiménez, and Claude Piguet. Maximizing Nanoscale Downshifting Energy Transfer in a Metallosupramolecular Cr(III)−Er(III) Assembly. Inorganic Chemistry Article ASAP (2024) DOI: 10.1021/acs.inorgchem.4c02397 https://hdl.handle.net/10481/93902 10.1021/acs.inorgchem.4c02397 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional American Chemical Society