inorganic chemistry

Ru^2 þcomplex and the dendrimer and emit in the NIR region with
line-like bands. In principle, the emission wavelength can be
tuned by replacing Nd^3 þ with other lanthanide ions possessing
low-lying excited states.

VI. Conclusion

The introduction of dendrimers as ligands has greatly expanded
the scope of metal coordination chemistry and, in particular, has
revitalized the study of luminescent metal complexes. The great
potential of dendrimers as light-absorbing ligands and the diver-
sityoftheircomposition,coupledwiththevarietyofmetalionsthat
can be involved and of the dendrimer–metal coordination
structures (Fig. 2), has allowed to build systems capable of
exhibiting very complex luminescence properties. Such systems
are quite suitable to get insight on the mechanisms of energy and
electron-transfer processes. Another important feature of this

E (10

3 cm

–1

)

15

10

5

20

30

25

0

5

(^1) MLCT
(^3) MLCT
het = 60 %
hisc~ 100 %
het = 90 %
[Ru(bpy) 2 (CN) 2 ]
S 0 S 0
S 1
T 1
Nd3+
(^4) Ij
(^4) F3/2
FIG. 16. Energy level diagram showing the excited states involved in
the main photophysical processes (absorption: solid lines; radiative
deactivation: dashed lines; nonradiative deactivation processes: wavy
lines) of the { 5 Nd^3 þ[Ru(bpy) 2 (CN) 2 ]} three-component system. For
the sake of clarity, naphthyl excimer energy level has been omitted.
132 VINCENZO BALZANIet al.