Chemistry Reference
In-Depth Information
The following compounds were obtained following the same reaction procedure:
(Q
5
){SiW
11
Cu} (
1
), (Q
5
){SiW
11
Fe} (
2
), (Q
6
){SiW
11
Cu} (
3
), (Q
6
){SiW
11
Fe} (
4
), (Q
7
){SiW
11
} (
5
),
(Q
7
){SiW
11
Cu} (
6
), (Q
7
){SiW
11
Co} (
7
), (Q
7
){SiW
11
Fe
III
} (
8
), (Q
7
){SiW
11
Ni} (
9
), (Q
7
){SiW
11
Cr}
(
10
), (Q
7
){SiW
11
Fe
II
} (
11
), (Q
7
){SiW
11
Mn} (
12
), (Q
8
){SiW
11
Cu} (
13
), (Q
8
){SiW
11
Fe} (
14
)
For the Q
7
-series iron was applied in its oxidation state of +II (
11
) and +III (
8
). Over a
period of several days the yellow colored compound (
11
)
turned the same color as its
brown colored Fe
III
analogue (
8
), which indicates an oxidation of the iron (II) to iron (III)
(by oxygen from air or the cluster itself). The compounds IR and UV-Vis spectra were
identical at this point and both compounds showed the same EPR-signal. As air-stable
ionic liquids were the main goal of this work, no further investigation of compound (
11
)
were undertaken which would have required glove box atmosphere or stabilizing agents
for the Fe(II) oxidation state.
3.1.3 Analysis of the synthesized Keggin clusters
3.1.3.1 Vibrational spectroscopy
The Keggin structure of the anions was evidenced by IR spectroscopy on a Shimadzu FT-
IR-8400S spectrometer by assignment of characteristic vibrations as they are listed in
literature.
[62]
TPA
THexA
THA
TOA
assignment
SiW
11
Cu
SiW
11
Fe
SiW
11
Cu
SiW
11
Fe
SiW
11
Cu
SiW
11
Fe
SiW
11
Cu
SiW
11
Fe
X
as
(X-O
c
)+
X
as
(W-O
t
)
1001 w
1001 w
1001 w
1002 w
1009 w
1001 w
1006 w
1003 w
X
as
(W-O
t
)
951 m
955 m
951 m
958 m
962 m
957 m
953 m
959 m
X
as
(W-O
c
) +
X
as
(W-
O
t
)sym
907 vs
910 vs
908 vs
912 vs
908 s
914 s
907 s
914 vs
X
as
(W-O
v
-W)
-
876 sh
-
878 m
-
879 m
878 m
X
as
(W-O
a
-W) +
X
as
(Cu-O)
a
802 vs
798 vs
804 vs
799 s
802
799 s
800 s
799 vs
X
as
(Cu-O)
689 m
-
692 m
-
689 m
-
689 w
-
G
(W-O
a
-W) +
G
(M-
O
c
)
540 w
527w
540 w
525 w
540 w
527 w
540 w
526 w
G
(W-O
b
-W) +
G
(M-
O
c
)
525 w
505 w
529 w
500 w
524 w
506
529 w
505
414 w
418 w
419 w
419 w
417 w
-
417 w
419 w
G
(W-O
b
-W)
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