A new class of dyes, platinum(II) and palladium(II) complexes of the porphyrin ketones (or "oxochlorins"), exhibiting strong phosphorescence at room temperature is described. Several representative compounds were prepared and studied by spectral luminescence methods in solution. Compared to the related porphyrin and chlorin complexes, the new dyes display high photochemical stability, long wave spectral characteristics, and good compatibility with semiconductor optoelectronics (e.g., excitation by light-emitting diodes). These properties make the new dyes promising for a number of relevant applications, such as quenched phosphorescence sensing and phosphorescence probing (e.g., in binding assays). Analytical application of the porphyrin ketone complexes to phosphorescence lifetime-based sensing of molecular oxygen is described. Platinum(II) octaethylporphine ketone was dissolved in a polystyrene layer to give an oxygen-sensitive film. Oxygen measurements were performed with a prototype fiber-optic instrument based on solid-state components, such as light-emitting diodes and photodiodes. The instrument measured phosphorescence lifetime via changes in phase shift The phosphorescence lifetime was determined to change from about 61.4 ps at zero oxygen to 16.3 ps in air (210 hPa of oxygen) at 22 °C. The analytically useful range of the sensor was 0-210 hPa of oxygen partial pressure, with a detection limit of 1.5 hPa. The precision of the device was 1.0 hPa at 210 hPa of oxygen and 0.5 hPa at zero oxygen.Platinum (II) and palladium (II) complexes of porphyrins are known to exhibit strong phosphorescence at room temperatures,1-4 with quantum yields of > 10%. Compared to most other types of phosphorescent organic dyes, porphyrin complexes have long (1) Eastwood, D.; Gouterman, M.

The design of luminescent oxygen sensors is guided by optimizing sensitivity and/or the form of the calibration function. Both qualities are governed by the molecular processes of luminescence quenching. To evaluate the influence of matrix effects, we prepared membranes based on oxygen-sensitive phosphorescent complexes of porphyrin ketones dissolved in plasticizer-free poly(vinyl chloride) (PVC) and polystyrene (PS). In a PVC matrix, both platinum(II) and palladium(II) octaethylporphyrin ketones exhibited perfectly linear Stern-Volmer intensity plots and almost single-exponential excited state decays. In a PS matrix, the sensitivity of palladium(II) octaethylporphyrin ketone was among the highest reported to date. Yet, slightly nonlinear Stern-Volmer plots and nonexponential decays illustrate the significance of matrix effects of PS. Addition of plasticizers to PVC-based sensors allowed tuning of the oxygen sensitivity in a wide range, while the Stern-Volmer plots became pronouncedly nonlinear. For the plasticizer bis(2-ethylhexyl) adipate, the decay profile was single-exponential in the absence but nonexponential in the presence of oxygen, which is attributed to a distribution of quenching rate constants.

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