We show in this paper how the
3ML
CT lumines
cen
ce of [Ru(bipy)(CN)
4]
2-, whi
ch is known to behighly solvent-dependent, may be varied over a mu
ch wider range than
can be a
chieved by solvent effe
cts,by intera
ction of the externally dire
cted
cyanide ligands with additional metal
cations both in the solid stateand in solution. A series of
crystallographi
c studies of [Ru(bipy)(CN)
4]
2- salts with different metal
cationsM
n+ (Li
+, Na
+, K
+, mixed Li
+/K
+, Cs
+, and Ba
2+) shows how the
cyanide/M
n+ intera
ction varies from the
conventional "end-on" with the more Lewis-a
cidi
c cations (Li
+, Ba
2+) to the more unusual "side-on" intera
ctionwith the softer metal
cations (K
+, Cs
+). The solid-state lumines
cen
ce intensity and lifetime of these saltsis highly dependent on the nature of the
cation, with Cs
+ affording the weakest lumines
cen
ce and Ba
2+ thestrongest. A series of titrations of the more soluble derivative [Ru(
tBu
2bipy)(CN)
4]
2- in MeCN with a rangeof metal salts showed how the
cyanide/M
n+ asso
ciation results in a substantial blue-shift of the
1MLCTabsorptions, and
3MLCT energies, intensities, and lifetimes, with the
complex varying from essentially non-lumines
cent in the absen
ce of metal
cation to showing strong (
![](/images/gif<font color=)
chars/phi.gif" BORDER=0 > = 0.07), long-lived (1.4
![](/images/entities/mgr.gif)
s), and high-energy (583 nm) lumines
cen
ce in the presen
ce of Ba
2+. This modulation of the
3MLCT energy, over arange of about 6000
cm
-1 depending on the added
cation,
could be used to reverse the dire
ction ofphotoindu
ced energy transfer in a dyad
containing
covalently linked [Ru(bipy)
3]
2+ and [Ru(bipy)(CN)
4]
2-termini. In the absen
ce of a metal
cation, the [Ru(bipy)(CN)
4]
2- terminus has the lower
3MLCT energy andthereby quen
ches the [Ru(bipy)
3]
2+-based lumines
cen
ce; in the presen
ce of Ba
2+ ions, the
3MLCT energyof the [Ru(bipy)(CN)
4]
2- terminus is raised above that of the [Ru(bipy)
3]
2+ terminus, resulting in energytransfer to and sensitized emission from the latter.