Chemistry Reference
In-Depth Information
3.1.3.3 Thermogravimetric analysis
The thermal stability of
1
-
12
was examined by thermogravimetric analysis under
helium atmosphere in a temperature range from room temperature to 800 °C with a
heating rate of 5 K/min. As all compounds showed similar thermogravimetric behavior,
the analysis is exemplified using compound
5
, (Q
7
)
6
[
D
-SiW
11
O
39
Cu(H
2
O)] (see Figure 18).
In a first step (T < 200-210
o
C), residual solvent and cluster-based water-ligands are lost
(weight loss between
ca.
1-11%). At higher temperatures, decomposition of the organic
cation is observed until a temperature of
ca.
400-450
o
C is reached, where all organic
materials have been fully decomposed. For detailed analyses, see Table 4 (page 43).
(Q
7
)
6
[
D
-SiW
11
O
39
Cu(H
2
O)]
100
0.1
90
0.0
80
-0.1
70
-0.2
60
-0.3
50
-0.4
210 °C
430 °C
40
-0.5
100
200
300
400
500
600
temperature T (°C)
Figure 18:
TGA of (Q
7
)
6
[
D
-SiW
11
O
39
Cu(H
2
O)]
obtained under He atmosphere with a heating rate of
5 °C/min. Relative mass m/m
0
as function of temperature (blue line) and its first derivative (black line).
When analyzing the thermal stability, the following trend was observed: Increase of the
alkyl chain length of the cations results in a slight decrease of thermal stability. This is
exemplified when comparing the Q
5
-based compounds (decomposition onset:
ca.
200/210 °C) with the Q
8
-based compounds (decomposition onset:
ca.
190/195 °C).
When comparing the influence of different metal substitution patterns (e.g. Cu
II
vs Fe
III
-
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