1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

Discussion and Results 3
3.2.6.5.6 Conclusions from Investigations on the Structure-Properties-Relations
The investigations on variations of the fundamental structural elements elucidates that a
seven-membered exocycle is of significant relevance whereas oppositely lying substituents,
like e.g. the methyl group in 53, seem to be less relevant. That particular kind of annulation
seems to provide a sufficient distortion level in the porphyrin macrocycle structurally and
energetically while it stabilizes the systems configuration at the same time. A six-membered
connection appears more flexible and too influencing on the porphyrin core due to
enhanced conjugational effects. Thus, the second seven-membered ring structure 57 should
also give rise to separable enantiomers while the six-membered ring analog 58 should not.
For the latter, it is more likely that the flexibility of 58 leads to a dynamic equilibrium of
enantiomeric structure being non-resolvable as it is the case for dodeca-substituted system
56. For clarification, investigations by chiral HPLC-CD coupling are currently in progress.
Thus, for the further development on that kind of system in terms of PDT applications, the
basic structure was to be preserved to a large extend since the performance can significantly
change although only minor changes are implemented (57 and 58 only differ by one -CH2-
group!).
As then, the principle features of the kind of annulation have been investigated, it seemed
worth to study the effect, a poly-annulation might cause on the system’s behavior.
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