1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

3 Discussion and Results
diastereotopic protons on position 13 2 showing a typical 2 J coupling of 19.8 Hz. The
successful displacement of the phytyl side chain by methanol is proven by the lacking of the
corresponding aliphatic signals and the appearance of a singlet at 3.61 ppm (17 4 ). The oddly
seeming split-up for the NH-resonances into two distinct singlets at 0.37 and -1.75 ppm is
quite normal as the spectrum was recorded at the “high” concentration of approx. 0.08 M.
Then, pheophorbides tend to organize themselves to form large aggregates of specific
orientation by increased π-π interactions inducing selective ring current shifts. 84
28
8.0 7.95 7.9 6.3 6.2 6.1
10
5 20
3 1
3 2
trans
*
**
5.25 5.15 5.05
3 2
3 2
cis
13 2
12 1
8 1
18 17
N
NH HN
* CDCl3 ** CH2Cl2 **
* H2O 10 8 6 4 2 0 δ [ppm] -2
21 71 17 4
8 2
17 1 , 17 2
Figure 10. 1 H NMR spectrum of Me-33, 400 MHz, CDCl3, rt. All signals are numbered
according to IUPAC recommendations.
The spectroscopic data for 33 was identical except the fact that the signal at 3.61 ppm,
representing the methyl group of the ester, was lost.
18 1
**
*
N
Me-33
The UV/Vis spectrum 73a,84,85 of Me-33 being displayed in Figure 11 appears of typical shape
for porphyrins consisting of a SORET in the blue region and Q-bands in the red region of the
spectrum (see Figure 5). Since the compound is a mostly exclusively β-substituted chlorin,
the intensities differ quite a lot from those observed for meso-substituted tetraaryl-
porphyrins. The SORET absorption in Me-33, although representing the most intense one,
NH
O
O
O
NH