Observation of Room‐Temperature Deep‐Red/Near‐IR Phosphorescence of Pyrene with Cycloplatinated Complexes: An Experimental and Theoretical Study

Pyrene‐containing cyclometallated PtII complexes, with the pyrene moiety directly cyclometallated (Pt‐1) or connected to a 2‐phenylpyridine (ppy) ligand through a C–C (Pt‐2) or C≡C bond (Pt‐3), and a control complex with a phenyl group attached to the ppy ligand (Pt‐4) have been prepared. Room‐temperature deep‐red/near‐IR (NIR) phosphorescence emission (650–800 nm) was observed for Pt‐1, Pt‐2 and Pt‐3, whereas Pt‐4 showed emission at 528 nm. We found that Pt‐2, in which the pyrene moiety is not directly cyclometallated, shows intense pyrene‐based phosphorescence, which contrasts with a previous report that direct cyclometallation is necessary for the observation of the phosphorescence of pyrene in cyclometallated complexes. Besides the phosphorescence emission in the deep‐red/near‐IR range, a fluorescence emission band at higher energy was observed. Thus, these complexes can be described as unichromophore multi‐emissive materials. Normal 3MLCT/3IL emission at 528 nm was observed for Pt‐4. The UV/Vis absorption and phosphorescence emissions of the complexes were rationalized by DFT/TDDFT calculations. Theoretical calculations propose pyrene‐localized T1 states (3IL) for Pt‐1, Pt‐2 and Pt‐3, which is supported by the experimental results. The complexes were used in luminescent O2‐sensing experiments. These studies will be helpful in the development of room‐temperature phosphorescent materials and their application as luminescent molecular sensing or electroluminescent materials are promising.