This pape
r p
resents the synthesis, MO calculations, and photochemical and photophysical p
rope
rties of
cis-[Ru(bpy)
2(3Amdpy
2oxaNBE)](PF
6)
2 (
2), whe
re bpy is 2,2'-bipy
ridine and 3Amdpy
2oxaNBE is the novel 5,6-bis(3-amidopy
ridine)-7-oxano
rbo
rnene chelate-ligand (
1). Complex
2 is conside
red in
relation to the
cis-[Ru(bpy)
2(3Amnpy)
2](PF
6)
2 (
3) analogous complex, whe
re 3Amnpy is 3-aminopy
ridine. Complexes
2 and
3 exhibit abso
rptionsnea
r 350 nm and in the 420-500 nm
region att
ributable to a cont
ribution f
rom MLCT t
ransitions (d
rs/pi.gif" BORDER=0 > ![](/images/entities/<font color=)
ra
rr.gif"> bpy andd
rs/pi.gif" BORDER=0 > ![](/images/entities/<font color=)
ra
rr.gif"> L; L = 3Amdpy
2oxaNBE o
r 3Amnpy). Whe
reas complex
3 is photochemically
reactive, complex
2 showsluminescence eithe
r at 77 K o
r at
room tempe
ratu
re in fluid solution. The emission of
2 assignable as an MLCT(Ru
![](/images/entities/<font color=)
ra
rr.gif"> bpy) emission is cha
racte
rized by a long lifetime at
room tempe
ratu
re (650 ns in CH
3CN and 509 ns inH
2O). It is independent of
![](/images/gifcha<font color=)
rs/lambda.gif" BORDER=0 >
irr, but it is tempe
ratu
re dependent; i.e., it inc
reases as the tempe
ratu
re is lowe
red.Conside
ring the chelate
ring of
1 cont
ributes to the stability of the complex
2 unde
r continuous light i
rradiation, thediffe
rence in the p
rima
ry photop
rocesses of
3 (loss of 3Amnpy) and
2 (luminescence) may be caused by a lowe
ringof the lowest excited state f
rom
3 to
2. The su
rface c
rossing to the lowest MC state value of 987 cm
-1 (simila
r tothat of [Ru(bpy)
3]
2+) will be p
revented in the case of complex
2, and as a
result, efficient 3Amdpy moiety losscannot occu
r. The elect
ronic depopulation of the {Ru(bpy)
2} unit and population of a bpy* o
rbital upon excitationa
re evident by compa
ring the photophysical p
rope
rties with those of a [Ru(bpy)
3]
2+ related complex. Mo
reove
r, a
reduction of a bpy ligand in the MLCT excited state is indicated by time-
resolved spect
ra that show featu
res typicalof bpy
-. The photocatalytic p
rope
rty of
2 is spect
roscopically demonst
rated by oxidative quenching using eithe
rmethylviologen
2+ o
r [RuCl(NH
3)
5]
+2 elect
ron-accepto
r ions.