Metal luminescence

If d>M cannot be measured, it may be substituted, as in Eq. 2, by the efficiency of the metal luminescence (i/M), which is derivable from Eq. 3. Since in this study the radiative (kr), and nonradiative (kar) rate constants are calculated from the experimentally obtained lifetimes, Eq. 3 may be replaced by Eq. 4 on the assumption that the decay of the metal emitting state in D20 at 77 K is purely radiative. 

Encapsulation of the Eu3 + and Tb3 + ions by cage-like ligands was also achieved using functionalized calixarenes. Metal luminescence properties were studied mostly for complexes of calix[4]arenes, while few results are available for complexes of calix[6]arenes and calix[8]arenes, with the latter being dinuclear complexes. Figure 13 schematically shows the calixarene ligands of the Eu3+ and Tb3+ complexes examined. Some photophysical data and the number of coordinated solvent molecules of these complexes are gathered in Table 4. 

In the following discussion, we analyze some factors responsible for the Eu3+ and Tb3+ luminescence intensity, that is the efficiencies of the ligand absorption, of the ligand-metal energy transfer, and of the metal luminescence. Furthermore, we compare the intensities of the metal luminescence... 

In order to discuss the efficiency of the metal luminescence in the complex, the radiative and nonradiative decay rate constants of the Eu3+ 5D0 and Tb3+ 5D4 emitting states (Table 6) have been calculated using Eqs. 10-12. 

TABLE 6. Decay Rate Constants of the Metal Luminescent States and Number of Solvent Molecules Coordinated to the Metal Ion11... 

In this section, we discuss the intensity of the metal luminescence obtained upon ligand excitation on the basis of the product of the metal luminescence quantum yield upon excitation at a certain wavelength and the molar absorption coefficient of the ligand in the complex at the same wavelength (Table 7). We would like to recall that the metal luminescence intensity is the photophysical property of main interest in this research dealing with the antenna effect in Eu3+ and Tb3+ complexes. Furthermore, this quantity is determining for some applications of these compounds (Section III). 

---