Temperature Dependence of the Phosphorescence Spectra of a Vanadyl Protoporphyrin Complex

Upon an interaction of protoporphyrin IX free base with an excess of vanadyl sulfate in refluxing dimethylformamide, corresponding vanadyl protoporphyrin is obtained in a high yield. The structure of vanadyl protoporphyrin is determined by the data of EAS and mass spectrometry. An analysis of the temperature dependence of the phosphorescence spectra of a polystyrene film including vanadyl protoporphyrin is conducted upon thermostating using a cryostat. It is found that, throughout the entire range of temperatures of from –195 to 25°C, the ratio of the intensity of transitions of phosphorescence 4T1–2S0 and 2T1–2S0 changes gradually and completely reversibly without hysteresis effects. An analysis technique of phosphorescence spectra of vanadyl protoporphyrin for the determination of temperature by the shape of a phosphorescence spectrum that contains one pronounced maximum with a set of shoulders in the red visible region is proposed.