inorganic chemistry

efficiency from the^3 MLCT excited state of [Ru(bpy) 2 (CN) 2 ] to Nd^3 þ
can be assumed to be equal to the efficiency of the quenching of the
[Ru(bpy) 2 (CN) 2 ] emission (ca. 90%) because quenching by electron
transfer can be ruled out in view of the Nd^3 þredox properties. No
evidence of energy transfer in the adduct from the naphthyl-
localizedT 1 excited state of the dendrimer to the lowest^3 MLCT
state of [Ru(bpy) 2 (CN) 2 ] has been found since no change in theT 1
lifetime at 77 K has been observed.
The three components of the self-assembled structure have com-
plementary properties so that new functions emerge from their
assembly. Dendrimer 5 has a very high molar absorption coeffi-
cient in the UV spectral region because of 12 dimethoxybenzene
and 16 naphthyl units, but it is unable to sensitize the emission
of an Nd^3 þion placed in its cyclam core. The [Ru(bpy) 2 (CN) 2 ] com-
plex can coordinate (by the cyanide ligands) and sensitize the
emission of Nd^3 þions. Self-assembly of the three species leads to
a quite unusual Nd^3 þ complex which exploits a dendrimer and
an Ru^2 þ complex as ligands. Such a system behaves as an
antenna that can harvest UV to VIS light absorbed by both the

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

{ 5 •Nd3+•[Ru(bpy) 2 (CN) 2 ]}

O

O

O

O

O

O

O

O

N

Nd3+

N

N

N

L

L

N

N

N

N

N

N

C

C

Ru

FIG. 15. Schematic representation of a metal complex based on den-
drimer 5 , one Nd^3 þ and [Ru(bpy) 2 (CN) 2 ] complex, and the
corresponding scheme (Fig. 2f).

PHOTOCHEMISTRY & PHOTOPHYSICS OF METAL COMPLEXES 131