Chemistry Reference
In-Depth Information
(a)
2
1
e
0
(b)
0.8
0.4
A
0.0
(c)
0.8
e
0.4
0.0
400
600
l
(nm)
800
1000
Figure 8.13
UV-Vis spectra of: (a) [Co
III
(
Me
L
1
OMe
)
•
(acac)]
2+
in dichloromethane; (b) [Co
III
(L
4
tBu
)
•
(acac)]
2+
in
acetonitrile; and (c) [Co
III
(L
14
ISQ
)
•
(tren)]
2+
in dichloromethane. (Adapted from [64], [84] and [76].) (a) and (c):
value in 10
4
M
−1
cm
−1
ε
(b): Absorbance of a 0.5mM solution. (Reprinted from [64], copyright 2000, with
permissionfromElsevier.)
redox couple at the lower value of 0.08 V. Bulk electrolysis of [Co
II
(L
13
Bz
)
2
]at0.35Vor[Co
III
(L
13
Bz
)
3
]
at 0.08 V affords a similar oxidized species that has been identified as [Co
III
(L
13
Bz
)
2
(L
13
Bz
)
•
]
+
. There-
fore, [Co
II
(L
13
Bz
(L
13
Bz
)
•
]
+
is likely formed as a transient species upon oxidation of [Co
II
(L
13
Bz
)
)
2
], and
rearranges into [Co
III
(L
13
Bz
)
•
]
+
. The increased steric bulk of the diphenylimidazole relative to the
benzimidazole moiety has been proposed to account for the different behavior observed for [Co
II
(L
13
Ph
)
2
(L
13
Bz
)
2
]
and [Co
II
(L
13
Bz
)
2
].
A series of octahedral cobalt(III) complexes has been prepared from tetradentate N
3
O tripodal ligands.
84
The octahedral coordination sphere of the metal is completed with an additional bidentate ligand, either
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