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Fig. 9.35 Electronic absorption spectra of [Ni
2
(EtCS
2
)
4
I]
1
(8), [Ni
2
(
n
-PrCS
2
)
4
I]
1
(9), and
[Ni
2
(
n
-BuCS
2
)
4
I]
1
(10) in the solid state (KI pressed disks), together with that of [Ni
2
(EtCS
2
)
4
]
[
38
]. The
inset
shows the schematic energy-band structure of [Ni
2
(MeCS
2
)
4
I]
1
estimated by
the unrestricted hybrid DFT calculation (UB3LYP) methods using the dimer and tetramer
models
Table 9.6 Electronic absorption spectral data of 7-10 in the solid-state [
38
,
82
]
Compound Wavenumber/10
3
cm
1a
[Ni
2
(EtCS
2
)
4
][
38
] 13.5 (sh), 18.6 (sh), 22.7, 28.2
[Ni
2
(
n
-PrCS
2
)
4
][
38
] 12.6 (sh), 17.4 (sh), 22.6 (sh), 27.2 (sh), 29.6
[Ni
2
(
n
-BuCS
2
)
4
][
38
] 13.4 (sh), 18.5 (sh), 22.2, 27.5
[Ni
2
(MeCS
2
)
4
I]
1
(7)[
82
] 5.2 (650 meV)
b
[Ni
2
(EtCS
2
)
4
I]
1
(8)[
38
] 5.4, 14.7, 22.0 (sh), 29.3
[Ni
2
(
n
-PrCS
2
)
4
I]
1
(9)[
38
] 5.6, 14.8, 21.1 (sh), 30.7
[Ni
2
(
n
-BuCS
2
)
4
I]
1
(10)[
38
] 5.5, 14.9, 21.0 (sh), 30.7
a
Measured using KBr pressed disks for [Ni
2
(RCS
2
)
4
] (R = Et,
n
-Pr,
n
-Bu) and using both KBr and
KI disks for 8-10 at 298 K.
b
Only a strong absorption band observed in near-IR region was reported [
82
].
mainly composed of I 5p
z
orbitals. In order to estimate transfer energy
t
and on-site
Coulomb repulsion energy
U
in the bulk, the following equations concerning
t
,
U
,and
an effective exchange integral
J
are used [
42
,
83
,
84
].
ðE
LS
E
HS
2
Þ
J ¼
DE
HS
DE
LS
S
S
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