inorganic chemistry

photocatalyst, whilefac-Re(bpy)(CO) 3 (CN) ( 8 ), which also possess
an anionic ligand, cannot photocatalyze CO 2 reduction (63,64).
The substituents on the bipyridine ligand are also of importance
( 65 ). The complex 3c, which has electron-withdrawing CF 3
groups, shows only low CO 2 -reducing abilities (FCO¼0.005). How-
ever, the introduction of electron-donating MeO groups did not
influence the photocatalytic ability of the rhenium complex3j.
A strong correlation between the first reduction potential
and the photocatalytic ability of rhenium complexes has
been reported( 65 ). For example, complexes withE1/2red>
1.4V
versus Ag/AgNO 3 show only low photocatalytic ability for CO 2

TABLE VII

PHOTOCATALYTICCO 2 REDUCTIONUSINGRHENIUM(I) BIPYRIDINECOMPLEXES.

X

N

N

L¢

L

Re

CO

CO 2

n+

CO

CO

hn (365 nm)

DMF-TEOA (5:1 v/v)

X

Rhenium complex

Entry X L L^0 nE1/2reda(V) FCOb Ref.

(1)fac-[Re(4,4^0 -X 2 -bpy)(CO) 3 L]nþ
1a H Cl
CO 0
1.67 0.14 (60,64)
3a H P(OEt) 3 CO 1
1.43 0.38 (61,65)
3j MeO P(OEt) 3 CO 1
1.67 0.33 ( 64 )
3c CF 3 P(OEt) 3 CO 1
1.03 0.005 ( 65 )
3f H PPh 3 CO 1
1.40 0.05 (62,65)
2a H py CO 1 0.03 ( 29 )
12 H NCS
CO 0
1.61 0.30 ( 64 )
8 H CN
CO 0
1.67 0 ( 64 )
MS MeO P(OEt) 3 CO 1
1.67 0.59 ( 64 )
H CH 3 CN CO 1
1.49c
13 H CH 3 CN CO 1
1.49c 0.04 ( 64 )
14 H OCHO
CO 0
1.72c 0.05 ( 62 )
(2)cis,trans-[Re(4,4^0 -X 2 -bpy)(CO) 2 LL^0 ]nþ
11a H P(OEt) 3 P(OEt) 3 1
1.69 0( 66 )
11d Me P(p-FPh) 3 P(OMe) 3 1
1.74 0.09 (33,67)
11e Me P(p-FPh) 3 P(p-FPh) 3 1
1.73 0.20 (33,67)
11f Me P(Oi-Pr) 3 P(Oi-Pr) 3 1
1.86 0.02 (33,67)

aReduction potentials of the complexes versus Ag/AgNO 3 measured in CH 3 CN.

bQuantum yields of CO formation.

cReduction potential converted from Ref.( 71 ) withE1/2redversus Fc/Fcþþ0.09 V.

RHENIUM(I) DIIMINE COMPLEXES 169