1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

Discussion and Results 3
multiplicities of certain signals. For example, the ethyl group in Me-33 is providing a quartet
at 3.60 ppm for CH2 (8 1 ) and a triplet for CH3 at 1.64 ppm (8 2 ) while in the conjugate the
corresponding signals are obtained as two multiplets at 3.38 and 3.42 ppm for position 8 2
and as a quartet at 1.42 ppm. As both systems cannot electronically communicate due to the
saturated linkage, these facts hint to the adoption of a preferential equilibrium
conformation where both dye molecules are in close proximity towards each being a good
prerequisite for FRET.
The UV/Vis spectrum of 94 also appears more or less as sum spectrum of the precursor
compounds with preserved spectral positions like it is depicted in Figure 51.
1.2
A rel [a.u.]
1.0
0.8
0.6
0.4
0.2
0
suitable
PDT-absorption
300 400 500 600 700 λ [nm] 800
Figure 51. Overlaid absorption spectra of conjugate 94 and precursors 33 and 92 measured
in DMF with marked excitation region for PDT applications.
Nicely, the absorption in the more red-lying region of the spectrum is preserved with the
relatively high extinction coefficient of approximately 30000 M -1 ·cm -1 being well suited for
PDT applications as it provides a deep enough penetration of tissue at sufficient absorption.
Exact values are gathered in Table 25.
33
92
94
127