Phenylacetylide ligand mediated tuning of visible-light absorption, room temperature phosphorescence lifetime and triplet–triplet annihilation based up-conversion of a diimine Pt(II) bisacetylide complex

•The impact of linked coumarin ligands on the photophysics of diimine Pt(II) bisacetylide complexes were investigated.•A room temperature long-lived phosphorescence of the coumarin was observed.•A general strategy of direct metalation of the organic chromophore is proposed.•The Pt(II) complexes were efficient as triplet sensitizers for triplet–triplet annihilation upconversion.

We addressed the impact of coumarin ligands linkage on the photophysics of a series of diimine Pt(II) bisacetylide complexes. The long-lived room temperature phosphorescence of the coumarin unit was observed (λem = 636 nm, ΦP = 0.2%, τT = 20.15 μs) within the complex Pt(dbbpy)(CC-phenylene-coumarin)2, where dbbpy stands for 4,4′-di(tert-butyl)-2,2′-bipyridine and CC-phenylene-coumarin is 6-(4′-ethynylphenyl)-coumarin. Comparison with the alternative complex Pt(dbbpy)(CC-coumarin)2 which has ɛ = 32,300 M−1 cm−1 at 404 nm, where CC-coumarin stands for 6-ethynylcoumarin, revealed that Pt(dbbpy)(CC-phenylene-coumarin)2 also showed strong absorption in the visible range (ɛ = 71,900 M−1 cm−1 at 407 nm). The emissive triplet excited state of Pt(dbbpy)(CC-phenylene-coumarin)2 was characterized as 3IL and the extension of the π-conjugation system inside the coumarin ligand was found account for elongation of the lifetime of triplet excited states. Inspired by its unusual phosphorescence behavior, Pt(dbbpy)(CC-phenylene-coumarin)2 was used as the sensitizer for the triplet–triplet annihilation based upconversion and the observed upconversion quantum yield was up to 19.7%.

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