Chemistry Reference
In-Depth Information
Compound
no
compound formula
metal salt used
charge of
cluster anion
melting range
(°C)
(Q
5
)
6
[D-SiW
11
O
39
Cu(H
2
O)]
1
Cu(NO
3
)
2
ڄ
3H
2
O
6-
200-210
(Q
5
)
5
[D-SiW
11
O
39
Fe(H
2
O)]
FeCl
3
ڄ
6H
2
O
5-
220-228
2
(Q
6
)
6
[D-SiW
11
O
39
Cu(H
2
O)]
6-
120-130
3
Cu(NO
3
)
2
ڄ
3H
2
O
(Q
6
)
5
[D-SiW
11
O
39
Fe(H
2
O)]
4
FeCl
3
ڄ
6H
2
O
5-
78-90
(Q
7
)
6
[D-SiW
11
O
39
Cu(H
2
O)]
6
Cu(NO
3
)
2
ڄ
3H
2
O
6-
RT-IL
(Q
7
)
6
[D-SiW
11
O
39
Co(H
2
O)]
7
Co(NO
3
)
2
ڄ
6H
2
O
6-
RT-IL
(Q
7
)
5
[D-SiW
11
O
39
Fe(H
2
O)]
FeCl
3
ڄ
6H
2
O
5-
RT-IL
8
(Q
7
)
6
[D-SiW
11
O
39
Ni(H
2
O)]
9
NiCl
2
ڄ
6H
2
O
6-
RT-IL
(Q
7
)
5
[D-SiW
11
O
39
Cr(H
2
O)]
10
Cr(NO
3
)
3
ڄ
9H
2
O
5-
RT-IL
(Q
7
)
6
[D-SiW
11
O
39
Mn(H
2
O)]
12
MnCl
2
ڄ
4H
2
O
6-
RT-IL
13
(Q
8
)
6
[D-SiW
11
O
39
Cu(H
2
O)]
CuCl
2
ڄ
2H
2
O
6-
RT-IL
14
(Q
8
)
5
[D-SiW
11
O
39
Fe(H
2
O)] FeCl
3
ڄ
6H
2
O 5- RT-IL
Table 5
Overview of all compounds of the type (Q
x
)
n
[
D
-XW
11
O
39
TM(H
2
O)] showing the transitionmetals
used for derivatizing the lacuna, the cluster charges and melting ranges.
A comparison of the melting ranges shows that longer alkyl chains result in lower
melting points which is nicely seen at hand of the [
D
-SiW
11
O
39
Cu(H
2
O)]
6-
-based
compounds
1
,
3
,
6
,
13
where the melting range decreases as the cation alkyl chain
length increases from Q
5
(m.p. 200-210
o
C) to Q
8
(RTIL). The behavior can be explained
by the increasing steric demand of the longer chains. This results in lower electrostatic
interactions between cation and anion, due to increased cation-anion distances. As a
result, lower melting points are observed for longer alkyl chains. When studying the
influence of the cluster charge and therefore, the number of counter cations, an
interesting trend is observed: a higher number of counter ions results in a decreased
melting point. The melting point of compound
1
(cluster charge: 6-) is approximately 20
o
C lower than the melting point of
2
(cluster charge: 5-). The effect is increased with
increasing cation size: while the difference in melting point for the Q
5
-based compounds
1
and
2
is
ca
. 20
o
C, the related, Q
6
-based compounds
3
and
4
feature a melting point
difference of
ca.
40
o
C.
In order to determine the melting points and gain insight into the melting behavior of
the ionic liquid products differential scanning calorimetry (DSC) was used. The
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