Abstract— The values of the absolute quantum yields of fluorescence and of intersystem crossing have been obtained for porphin and its derivatives by methods based on relative measurements involving flash photolysis. For a given compound the sum of these quantum yields is unity within experimental error which shows that the energetics of the molecules investigated is determined by competition of only two processes, viz., fluorescence and intersystem crossing, while internal conversion plays a negligible role. The values of the corresponding transition probabilities have been determined with the help of phase‐fluorometric measurements. The dependence of the transition probabilities on molecular structure is discussed.

The processes of the energy deactivation of electronic excitation in Yb(III) β-diketonates and their dependence on the nature of β-diketone and the second ligand as well as the environment and its state (complexes in organic solvents and polymer matrix) were studied. Taking as an example the ytterbium thenoyltrifluoroacetonate, it was shown that the energy losses in the ligand and Yb(III) ion, which is due to the high-frequency vibrations of the central C-H group of the β-diketone, can lead to the decreased quantum yield of the luminescence. The increase in the medium rigidity causes the decrease in losses in the ligand, but does not affect the deactivation of the Yb(III) ion excited level. In the mix-ligand complexes the second ligand (1,10-phenanthroline) improves the screening of the central ion providing almost full transfer of the energy, absorbed by ligand, to ytterbium ion.

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