Iridium(III) Complexes Bearing Pyrene‐Functionalized 1,10‐Phenanthroline Ligands as Highly Efficient Sensitizers for Triplet–Triplet Annihilation Upconversion

Abstract

"Chemistry-on-the-complex" synthetic methods have allowed the selective addition of 1-ethynylpyrene appendages to the 3-, 5-, 3,8- and 5,6-positions of Ir -coordinated 1,10-phenanthroline via Sonogashira cross-coupling. The resulting suite of complexes has given rise to the first rationalization of their absorption and emission properties as a function of the number and position of the pyrene moieties. Strong absorption in the visible region (e.g. 3,8-substituted Ir-3: λ =481 nm, ϵ=52 400 m cm ) and long-lived triplet excited states (e.g. 5-substituted Ir-2: τ =367.7 μs) were observed for the complexes in deaerated CH Cl . On testing the series as triplet sensitizers for triplet-triplet annihilation upconversion, those Ir complexes bearing pyrenyl appendages at the 3- and 3,8-positions (Ir-1, Ir-3) were found to give optimal upconversion quantum yields (30.2 % and 31.6 % respectively).

Impact of Alkyne Functionalization on Photophysical and Electrochemical Properties of 1,10‐Phenanthrolines and Their RuII Complexes

“…The complex C1 exhibits an octahedral coordination environment (Figure ) with expected N–Ru–N angles of 78.22° and 79.05° for the two 4,4′‐di‐ tert ‐butyl‐2,2′‐bipyridine (tbbpy) ligands and 79.79° for the alkynylated phenanthroline ligand L1 . Crystal structures of similar coordination compounds have already been published using 5,6‐dialkynylated 1,10‐phenenthrolines featuring comparable alkyne C–C distances of 1.203(9) Å in an Ir‐based system or 1.189(6) Å using Zn as central metal . This is in accordance to the alkyne C–C distance of C1 with 1.17(4) Å.…”

Ligand‐Tuneable, Red‐Emitting Iridium(III) Complexes for Efficient Triplet–Triplet Annihilation Upconversion Performance

“…TTA upconversion is of great interest due to the benefits that such processes can provide to the disciplines outlined earlier. A small number of reports have described the use of Ir III complexes for TTA upconversion, with the best performing, to date, being pyrene‐conjugated species of the type [Ir(ppy) 2 (L)]PF 6 (ppy=2‐phenylpyridine), which have demonstrated highly efficient upconversion quantum yields of up to 31.6 % (the highest value yet reported) . Typically, the sensitiser should possess good molar absorption at the wavelength of excitation and a long triplet lifetime …”

David Brown Award: S. Draper / Wiley–CST Green Chemistry Award: C. Wattanakit / Gottfried‐Wilhelm‐Leibniz‐Preis: W. Wernsdorfer

“…Drapers Forschung über die Synthese neuartiger polyaromatischer und lumineszierender Materialien führte kürzlich zu molekularen Materialien mit hohen Quantenausbeuten für Singulett‐Sauerstoff und Aufwärtskonversion. Sie berichtete in einer Angewandte‐Chemie ‐Zuschrift über Iridium(III)‐Komplexe mit pyrenfunktionalisierten 1,10‐Phenanthrolin‐Liganden als Sensibilisatoren der Triplett‐Triplett‐Annihilierungs‐Aufwärtskonversion, und ein Beitrag ihrer Gruppe über Phenanthrolin‐Ruthenium(II)‐Komplexe als Modellsysteme für Hochleistungs‐Triplettphotosensibilisatoren wurde auf dem Titelbild von ChemPhotoChem vorgestellt.…”