Exploiting coumarin-6 as ancillary ligands in 1,10-phenanthroline Ir(iii) complexes: generating triplet photosensitisers with high upconversion capabilities.

A series of new Ir(iii) complexes incorporating 3-(2-benzothiazolyl)-7-(diethylamino)coumarin (coumarin 6) and ethynylpyrene (EP) functionalised 1,10-phenanthroline (phen) were developed. [Ir(iii)(coumarin 6)2(3-EP-phen)](PF6) (Ir-3) proved to be the most promising material in triplet photosensitising applications. Highly absorbing at λ = 485 nm (ε = 1.31 × 105 M-1 cm-1), it exhibits high upconversion and singlet oxygen quantum yields (ΦUC = 27.5%, ΦΔ = 81.5%) and an exemplary upconversion capability (η = 3.60 × 106 M-1 cm-1).