inorganic chemistry

G. PHOTOCHEMICALREACTIONS OF THELIGAND INRe(I) COMPLEXES

Three types of photochemical reactions of the ligand in
rhenium(I) diimine carbonyl complexes have been reported by
several authors.
fac-[Re(bpy)(CO) 3 (4-cyanopyridine)]þ (2c) was irradiated at
355 nm in a CO 2 -saturated triethanolamine (TEOA)–DMF (1:5
v/v) solution givingfac-[Re(bpy)(CO) 3 (CN)] ( 8 ) with a 53% quan-
tum yield (Eq. 13) ( 53 ). This reaction proceeds via the photo-
chemical reduction of2cby TEOA.

CO

CO

hn (365 nm)

CO

in TEOA/DMF (1:5 v/v)

CO 2 sat. CO

CO

CO

2c

8

53%

CN

CN

N Re Re

N N

N

ð 13 Þ

The second example is the photoinduced alkylation of the
bipyridine ligand in fac-Re(bpy)(CO) 3 Br in the presence of
triethylamine (TEA) in a DMF solution (Eq. 14) ( 54 ).

0.002

0.000

0.000

1822

1810

1800 1850 1900 1820 1890 1960

Wavenumbers (cm–1) Wavenumbers (cm–1)

1950

1 ps

2000

1820 1830 1840 1810 1820 1830 1840

1000

500

100

50

10

2

1 ns

1000

500

100

50

3020

10

5

–0.002

–0.004

Δ Absorbance Δ Absorbance

–0.006 –0.016

–0.008

FIG. 16. Picosecond (left) and nanosecond (right) difference TR-IR
spectra of1ain MeCN measured at selected time delays after excita-
tion (ps pulse: 266 nm, 150 fs with Ti:Sapphire laser; ns pulse:
267 nm–1 ns with Nd:YAG laser). Experimental points are separated
by 4–5 cm
^1. Inset: expansion of the low-wavenumber region showing
the formation of the photoproduct band. Copyright 2007 American
Chemical Society.

166 HIROYUKI TAKEDAet al.