inorganic chemistry

A hybrid material has been synthesized by covalently fixing
fac-[Re(dmb)(CO) 3 (PPh 3 )]þwithin the 3.5 nm diameter pores of
a stable biphenyl-bridged mesoporous organosilica (Bp-PMO).
Efficient energy transfer from the biphenylene units to the rhe-
nium complex was observed. Irradiation of dispersed particles
of this material in CH 3 CN in the presence of TEOA using 280-
nm light enables the photocatalytic reduction of CO 2 ( 109 ). 4.4
times more CO was produced in comparison to the direct irradi-
ation of the rhenium complex with 350-nm light. Rhenium
complexes are known to decompose upon direct absorption of
280-nm light through CO elimination (see Section III.F) ( 51 ).
The organosilica framework demonstrates a filtering effect,
inhibiting direct excitation of the rhenium complex within the
PMO pore, thereby increasing the photocatalyst durability. Fur-
ther, the chain reaction that induces elimination of the PPh 3
ligand observed in DMF solution (see Section IV.A) was not seen
with the PMO hybrids. The cause for this is suspected to be that
after the CO 2 reduction, recoordination of PPh 3 to the rhenium
center occurs more readily due to the detached PPh 3 being
contained within the pore.

ACKNOWLEDGMENTS

We are grateful to Dr. Shane Telfer, Massey University for his
assistance in the preparation of this chapter.

Si

Si

Si

S

Si

Si

O

O

O

O

O

N

N

Re

PPh 3

CO CO

2

CO

CO

CO

+

TEOA

TEOA•+

O

O

O

O

O

O

O

SCHEME 9. Light-harvesting system consisting of periodic meso-
porous organosilica with the rhenium complex as the reaction center.

RHENIUM(I) DIIMINE COMPLEXES 181