Spectral-luminescent study of the porphyrin-diketones and their complexes.

Syntheses of octaethylporphine-diketone (OEPDK) and its platinum(II) and palladium(II) complexes (PtOEPDK, PdOEPDK) were optimized, and the dyes were isolated in a pure form in preparative quantities. They were characterized by the NMR, UV-VIS absorption and emission spectroscopy. Electronic spectra of these dyes (absorption and luminescence) were investigated in detail, and compared to corresponding porphyrins and porphyrin-monoketones. OEPDK showed a strong fluorescence at about 700 nm, while PtOEPDK and PdOEPDK showed very weak room-temperature phosphorescence in the region of 850-1100 nm and practically no fluorescence. Protonation mechanisms were studied for these dyes. Protonation at sites other than pyrrole nitrogen atoms was shown to occur, corresponding protomeric spectral forms are presented. The possibilities of the use of porphyrin-diketones as longwave fluorescent and phosphorescent probes are discussed.