inorganic chemistry

energies of these states can be controlled by systematic chemical
modification of the bipyridine and axial ligands. In doing so, the
energy gap between^3 MLCT and^3 LF states can be tuned. Such
modification effects are summarized as follows:

1. Modification of the bipyridine ligand with introduction of elec-
   tron-withdrawing (donating) groups at the 4,4^0 -positions

0

0

0

–1

–2

–3

1

1871 cm–1 2050 cm–1

2012 cm–1

2000 2100

Wavenumber (cm–1)

1900

–2

–8

–4

0

0

0.0

1.0

2.0

2 4 6 8 10

4 (a)

(b)

0

2

ΔAbsorbance

×^10

–2

ΔAbsorbance

×^10

–2

ΔAbsorbance

×^10

–2

ΔAbsorbance

×^10

–2

246810

Time (ms)

Time (ms)

0246810

Time (ms)

FIG. 10. TR-IR spectra of3ain a degassed CH 3 CN solution taken at
50 ns (a) and 5ms (b) after 355-nm laser excitation. The three small
figures are the decay traces for typical IR bonds. (Copyright 2002
American Chemical Society.)

RHENIUM(I) DIIMINE COMPLEXES 153