Synthesis of polypyridyl ruthenium complexes with 2-(1-aryl)-1H-imidazo[4,5-f]-1,10-phenanthroline ligand and its application for luminescent oxygen sensing

Abstract

Polypyridyl ruthenium (Ru) complexes 1–3 were prepared. Their photophysical properties were investigated by UV-Vis absorption and luminescence emission spectra. The luminescent lifetimes of these Ruthenium complex were prolonged by more than 5 folds (t = 2.50 ms for complex 3) when compared with the parent Ru complex 1 (t = 0.45 ms). We propose that the extended luminescent lifetime of complex 3 is due to the equilibrium between ³MLCT state and the pyrene localized ³π-π^* triplet state (³IL). The luminescent O₂-sensing property of the complexes in solution and the IMPEK-C polymer film were studied, and the O₂ sensing was quantified with the two-site model. The oxygen-sensing property of the Ru complexes can be improved by 104-fold with extension of the luminescent lifetimes. For example, the quenching constant K_SV was improved from 0.0023 Torr^−1 of 1 to 0.2393 Torr^−1 for 3. Our results demonstrated a versatile approach for the preparation of Ru (II) polypyridine complexes with extended luminescent lifetimes as functional materials, for example, for luminescent oxygen-sensing applications.

Keywords

phosphorescence / ruthenium / oxygen sensor / quenching / intraligand triplet state