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

摘要

"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-III-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: lambda(abs) = 481 nm, epsilon = 52 400 M-(1) cm(-1)) and long-lived triplet excited states (e.g. 5-substituted Ir-2: tau(T) = 367.7 mu s) were observed for the complexes in deaerated CH2Cl2. On testing the series as triplet sensitizers for triplet-triplet annihilation upconversion, those Ir-III 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).