Accessing the long-lived emissive 3IL triplet excited states of coumarin fluorophores by direct cyclometallation and its application for oxygen sensing and upconversion
(ICT) feature of the C⁁N ligands. Pt-2 shows longerphosphorescence lifetime (τ = 20.3 μs) than other complexes (below 2.0 μs). Furthermore, Pt-2 shows phosphorescence quantum yield Φ = 0.37, whereas Pt-3 and Pt-4 show much smaller Φ values (0.03 and 0.01, respectively). DFT/TDDFT calculations indicate 3IL triplet excited states for the complexes. The complexes were used as for luminescence O2 sensing