1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

3 Discussion and Results
voltammogram for Cu(II)-53 an additional, not pronounced irreversible process can be
detected whose origin is unclear. It might arise from the formation of an instable copper(I)
complex.
Altogether it can be stated that substances of the here presented synthetic cycloketo-
porphyrin type are acclaimed in equal measures to other porphyrin systems concerning their
coordination chemistry. In agreement with theory, the indium(III) and zinc(II) complexes
show good characteristics in terms of singlet oxygen sensitization with appropriate
absorption bands at 658 and 655 nm, respectively, and with extinction coefficients of
sufficient values. Especially interesting are the findings on In(III)-53 as such complexes could
be applied in terms of a combined photo-radio-therapy.
This therapeutic method would comprise tumor imaging and treatment by using one single
substance as the complex could also be formed using radioactive indium-111. This
radionuclide decays nearly exclusively (99 %) via electron capture with a half-life t½ of 2.8 d
to cadmium-111. The emitted γ-radiation can be excellently detected by radiation tubes or
scintillation counters providing a good tool to recognize tumorous tissue. Additional in situ
irradiation with laser-light concentrated on those areas would then allow a concurrent
photodynamic treatment. First investigations with highly charged porphyrin systems also
derived from the porphyrin building blocks used within this thesis showed that accumulation
and detection in tumor tissue is possible (mice experiments). 70b Investigations concerning
such an application of cycloketo-porphyrin systems have been started, but unfortunately, no
clear results could be obtained up to now.
3.2.4.2 Reactions Involving the Exocyclic Ketone Moiety
In establishing the exocycle by a FRIEDEL-CRAFTS annulation procedure, a ketone is generated
on the porphyrin core and therewith a functionality being desirable from a synthesist’s point
of view since that should allow a great variety of modifications. Some possible examples
gathered in Table 12 have been taken into account and corresponding transformations were
subjected to trials according to standard procedures or protocols known to literature. But
curiously, in most of the cases the starting material was recovered more or less
quantitatively. Sometimes, a conversion could be detected by TLC, but all efforts to isolate
and characterize any formed product failed.
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