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

“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 IrIII‐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: λabs=481 nm, ϵ=52 400 m−1 cm−1) and long‐lived triplet excited states (e.g. 5‐substituted Ir‐2: τT=367.7 μs) were observed for the complexes in deaerated CH2Cl2. On testing the series as triplet sensitizers for triplet–triplet annihilation upconversion, those IrIII 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). „Chemie‐am‐Komplex”‐Synthesemethoden ermöglichten die selektive Einführung von 1‐Ethinylpyrengruppen an den 3‐, 5‐, 3,8‐ und 5,6‐Positionen von IrIII‐koordiniertem 1,10‐Phenanthrolin durch Sonogashira‐Kreuzkupplung. Die Absorptions‐ und Emissionseigenschaften der Komplexe wurden in Abhängigkeit von der Zahl und Position der Pyreneinheiten systematisch untersucht (siehe Bild, DPA=9,10‐Diphenylanthracen).