Enhancing the Performance of Pt(II)-Based Oxygen Sensing Probes by Expanding the Scope of N,C-Chelate and Ancillary Ligands.
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A library of cyclometalated Pt(II) complexes have been established for their uses as luminescent probes for the detection of molecular oxygen. By varying the N,C-chelates of the OSPs (oxygen sensing probes), it was determined that benzothiophene-pyridyl chelates have greater sensitivities compared to the benzofuran-pyridyl and pyridyl-indole chelates. By further altering the backbone with the attachment of dimesityl boron, an enhancement in the oxygen sensitivity was observed, establishing borylation as a sensible strategy to improve an OSPs performance. The second part of this study examined phenyl-triazole N,C-chelate Pt(II) complexes as OSPs and it was observed that functionalization with a diphenyl amine moiety substantially increased the quenching of phosphorescence. These changes are mainly due to the increase in phosphorescence decay lifetime allowing for a greater interaction between the excited state complex and O2, leading to efficient quenching. Majority of the films showed high photostability due to minimal photobleaching (oxidation in the excited state), are fully reversible in conjunction with having acceptable sensitivities; paving the path for potential topical applications.