Chemistry Reference
In-Depth Information
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Cu
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Cu
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Figure 2.12. Scheme of the synthesis of CuPc by cyclotetramerization of
phthalonitrile with metallic copper.
Figure 2.12 shows the case of the formation of CuPc from
o
-dicyanobenzene
(Dahlen, 1939). CuPc is also produced by reacting phthalic anhydride, urea, a
copper/copper salt and ammoniummolybdate (acting as a catalyst) in a high-boiling
solvent such as
o
-nitrotoluene, C
6
H
3
Cl
3
or alkyl benzenes. The choice of the solvent
is very important as it plays a significant role in the generation of impurities. After
the completion of the reaction, the solvent is removed by vacuum distillation and
the crude product thus obtained is further purified by treatment with dilute acid
and alkali solutions to remove the basic and acidic impurities. The product thus
obtained is dried and pulverized. It is surprising that such a complex molecule is
relatively easily obtained in the laboratory as compared to the simpler and closely
related porphyrins. Porphyrins are tetrapyrrolic pigments widely occuring in nature
and playing very important roles in various biological processes. They are present
e.g., in hemoglobins and myoglobins, which are responsible for oxygen transport
and storage in living tissues, and in the enzyme peroxidase.
2.5 Really big molecules
The chemistry of organic synthesis today has the tactics or means to increase
the size of molecules by aggregating more and more parts resulting in complex
supramolecular structures. TTF can be sequentially added forming bi-TTF, bis-
TTF and so on, producing oligomers (Iyoda
et al.
, 2004). Bi-TTF can be obtained
by making use of Ullmann's reaction by coupling two iodo-TTFs mediated by
copper at about 410 K. At the single-molecule level this reaction may also be
