Th
is paper presents the synthes
is, MO calculat
ions, and photochem
ical and photophys
ical propert
ies of
cis-[Ru(bpy)
2(3Amdpy
2oxaNBE)](PF
6)
2 (
2), where bpy
is 2,2'-b
ipyr
id
ine and 3Amdpy
2oxaNBE
is the novel 5,6-b
is(3-am
idopyr
id
ine)-7-oxanorbornene chelate-l
igand (
1). Complex
2 is cons
idered
in relat
ion to the
cis-[Ru(bpy)
2(3Amnpy)
2](PF
6)
2 (
3) analogous complex, where 3Amnpy
is 3-am
inopyr
id
ine. Complexes
2 and
3 exh
ib
it absorpt
ionsnear 350 nm and
in the 420-500 nm reg
ion attr
ibutable to a contr
ibut
ion from MLCT trans
it
ions (d
images/gifchars/pi.gif" BORDER=0 > images/ent
it
ies/rarr.g
if"> bpy andd
images/gifchars/pi.gif" BORDER=0 > images/ent
it
ies/rarr.g
if"> L; L = 3Amdpy
2oxaNBE or 3Amnpy). Whereas complex
3 is photochem
ically react
ive, complex
2 showslum
inescence e
ither at 77
K or at room temperature
in flu
id solut
ion. The em
iss
ion of
2 ass
ignable as an MLCT(Ru
images/ent
it
ies/rarr.g
if"> bpy) em
iss
ion
is character
ized by a long l
ifet
ime at room temperature (650 ns
in CH
3CN and 509 ns
inH
2O). It
is
independent of
images/g
ifchars/lambda.g
if" BORDER=0 >
irr, but
it
is temperature dependent;
i.e.,
it
increases as the temperature
is lowered.Cons
ider
ing the chelate r
ing of
1 contr
ibutes to the stab
il
ity of the complex
2 under cont
inuous l
ight
irrad
iat
ion, thed
ifference
in the pr
imary photoprocesses of
3 (loss of 3Amnpy) and
2 (lum
inescence) may be caused by a lower
ingof the lowest exc
ited state from
3 to
2. The surface cross
ing to the lowest MC state value of 987 cm
-1 (s
im
ilar tothat of [Ru(bpy)
3]
2+) w
ill be prevented
in the case of complex
2, and as a result, eff
ic
ient 3Amdpy mo
iety losscannot occur. The electron
ic depopulat
ion of the {Ru(bpy)
2} un
it and populat
ion of a bpy* orb
ital upon exc
itat
ionare ev
ident by compar
ing the photophys
ical propert
ies w
ith those of a [Ru(bpy)
3]
2+ related complex. Moreover, areduct
ion of a bpy l
igand
in the MLCT exc
ited state
is
ind
icated by t
ime-resolved spectra that show features typ
icalof bpy
images/entities/bull.gif">-. The photocatalyt
ic property of
2 is spectroscop
ically demonstrated by ox
idat
ive quench
ing us
ing e
ithermethylv
iologen
2+ or [RuCl(NH
3)
5]
+2 electron-acceptor
ions.