Oxygen sensing properties of thianthrene and phenothiazine derivatives exhibiting room temperature phosphorescence: Effect of substitution of phenothiazine moieties

Four new derivatives of thianthrene and phenothiazine are reported as emitters for oxygen sensing. They exhibit both fluorescence and phosphorescence at room temperature. Effects of the substitution pattern of phenothiazine moiety on the thermal, electrochemical, emissive and oxygen sensing properties of the compounds are discussed. No phosphorescence at room-temperature was detected for deoxygenated solutions of the compounds. Room temperature phosphorescence of the different intensity was detected for the compounds being in crystalline or amorphous phase and for their dispersions in different polymeric matrices. Fast oxygen response (ca. 0.1 s) of room temperature phosphorescence was observed for only 1 wt.% of the dispersions in polymeric host. The highest oxygen sensitivity, was demonstrated for methylphenothiazinyl-disubstituted thianthrene dispersed in poly(methyl methacrylate). Stern-Volmer constant of 21·10−4 ppm−1 was obtained compared to those of 0.97·10−4, 1.22·10−4 and 2.1·10−4 ppm−1 observed for the dispersions of other compounds. Displaying possibility of oxygen detection by different chromaticity responses of emission of the developed compounds, strong yellowish-green emission with CIE1931 coordinate of (0.294, 0.503) was observed for one sample in the absence of oxygen; while, weak deep-blue emission with CIE1931 coordinate of (0.174, 0.141) was observed for the same sample in oxygen atmosphere.