1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

*
applied θ
↓
110 °C
90 °C
70 °C
50 °C
30 °C
20 °C
9 8.5 8 7.5 7 ←δ [ppm]→ 5.5 5 4.5 4
Discussion and Results 3
was therefore dissolved in 1,1,2,2-tetrachloro-1,2-dideuteroethane (TClE). Figure 18 displays
the obtained results.
Figure 18. 1 H VT-NMR spectra (400 MHz) of 53 at the given temperatures as solution in TClE,
reference spectrum (20 °C) as solution in CDCl3 (*).
The spectra clearly depict a coalescence phenomenon for the signals of the arylic protons on
the freely rotatable rings (left area in Figure 18) but not for any ring inversion process. The
heating-up therewith causes an enhanced rotation of the phenyl rings on positions 10, 15
and 20 (=X) balancing the differences in the chemical surroundings of the corresponding
protons resulting in two average signals at 8.14 ppm (ortho positions X 2/6 ) and at 7.81 ppm
(meta positions X 3/5 ), respectively. The resonances for the methylene group of the exocycle
(right area in Figure 18) appear unaffected by the raise of temperature. Also, there are no
observable changes in the resonances of the protons on the tethered phenyl ring. Thus it is
to be concluded that such systems are completely stable in conformation at room
temperature and even at elevated temperatures making the resolution of the enantiomers
shown in Scheme 32 possible in principle. The discussion on that topic will be continued in
paragraph 3.2.5.
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