1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

Discussion and Results 3
orbitals will show a more pronounced mingling. These changes, depicted in Figure 33, will be
observable in the photophysical as well as in the electrochemical datasets.
Figure 33. Calculated shapes of the frontier orbitals (top line: LUMOs, bottom line: HOMOs)
for compounds 53, 57 and 58 (left to right). 96,99
As the 1 H NMR spectra have already been briefly discussed, their comparison should be
focused on next.
3.2.6.5.2
1 H NMR Spectroscopy
Although all spectra prove the presence of C1 symmetric porphyrin compounds with
annulated ketone exocycles, the six-membered ring analog 58 appears well distinct from 53
and 57 containing seven-membered exocycles. The latter appear perfectly stable in
configuration while 58 does not. This could be proven by VT NMR as well as by the
characteristic splitting pattern for the arylic protons at room temperature, as in 53 and 57
the different half-spaces above and below the plane of the macrocycle are distinguishable
(distinct signals for individual protons) which is not the case for 58.
Nevertheless, the annulation is considered to give rise to a distortion in the porphyrin
macrocycle in each case consequently changing the rotational barriers of the peripheral
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