Coumarin phosphorescence observed with (NN)-N-boolean AND Pt(II) bisacetylide complex and its applications for luminescent oxygen sensing and triplet-triplet-annihilation based upconversion

A dbbpy platinum(II) bis(coumarin acetylide) complex (Pt-1, dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine) was prepared. Pt-1 shows intense absorption in the visible region (lambda(abs) = 412 nm, epsilon = 3.23 x 10(4) M-1 cm(-1)) compared to the model complex dbbpy Pt(II) bis(phenylacetylide) (Pt-2, lambda(abs) = 424 nm, epsilon = 8.8 x 10(3) M-1 cm(-1)). Room temperature phosphorescence was observed for Pt-1 ((IL)-I-3, tau(P) = 2.52 mu s, lambda(em) = 624 nm, Phi(P) = 2.6%) and the emissive triplet excited state was assigned as mainly intraligand triplet excited state ((IL)-I-3), proved by 77 K steady state emission, nanosecond time-resolved transient absorption spectroscopy and DFT calculations. Complex Pt-1 was used for phosphorescent oxygen sensing and the sensitivity (Stern-Volmer quenching constant K-SV = 0.012 Torr(-1)) is 12-fold of the model complex Pt-2 (K-SV = 0.001 Torr(-1)). Pt-1 was also used as triplet sensitizer for triplet-triplet-annihilation based upconversion, upconversion quantum yield Phi(UC) up to 14.1% was observed, vs. 8.9% for the model complex Pt-2.