1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

3 Discussion and Results
Table 10. Photophysical parameters for Zn(II)-53 and In(III)-53 in comparison to free base
53.
66
λfl [nm] a
τ [ns] b
Φfl c
Zn(II)-53 702 0.6 0.02 0.08 0.90 0.86
In(III)-53 689 0.3 0.01 0.17 0.82 0.74
53 716/695 g
1.15/3.3 g
ΦIC d
ΦISC e
ΦΔ f
0.03 0.09 0.88 0.85
a
maximum in the fluorescence spectra in DMF at 532 nm excitation wavelength
b
fluorescence decay time determined in DMF via TCSPC at 532 nm excitation wavelength
c
d
quantum yield of fluorescence in DMF with pyropheophorbide a 33 (Φfl = 0.28) as reference
quantum yield of internal conversion in DMF
e
quantum yield of intersystem crossing in DMF determined via ps-TAS
f
quantum yield of singlet oxygen generation in DMF with 5,10,15,20-tetraphenylporphyrin 15 (Φfl = 0.65) as reference 88
g values for the two present tautomeric structures of 53
Measurements using the ps-TAS technique 96,109 and singlet oxygen luminescence 96,111
provided corresponding ΦISC and ΦΔ values being slightly lower for In(III)-53 compared to
free base 53 while Zn(II)-53 gives rise to nearly identical values. Thus, no further
enhancement of transition via intersystem crossing or singlet oxygen generation can be
achieved by insertion of zinc(II) or indium(III) while both complexes still are well suited for
PDT applications.
The electrochemical behavior was studied for all metal complexes in focus by cyclic
voltammetry analog to free base 53 (see paragraph 6.1). The obtained voltammograms are
depicted in Figure 28 and determined half-wave potentials are given in Table 11.
Table 11. Determined half-wave potentials, E½, for selected metal complexes of 53 in
comparison to the free base system given in V vs. ferrocene E(Fc/Fc + ) = +0.53 V (see
paragraph 6.1 for procedure details). Values in italics refer to literature data for metal
complexes of TPP 15 or the free base.
Compound E½ Red2 [V] E½ Red1 [V] E½ Ox1 [V] E½ Ox2 [V] Ref.
Cu(II)-53 (-1.35) a -1.80 -0.99 -1.33 +1.01 +0.98 +1.37 +1.21 117
Ni(II)-53 - - b
-1.01 -1.23 +1.09 +1.10 +1.39 +1.22 118
In(III)-53 -1.16 -1.48 -0.81 -1.09 +1.22 +1.16 +1.52 +1.45 119
Zn(II)-53 -1.39 -1.84 -1.04 -1.39 +0.90 +0.78 +1.13 +1.11 120
53 -1.23 -1.45 -0.95 -1.14 +1.02 +1.05 +1.25 +1.35 112
a not conclusive as peaks are only sparsely pronounced
b no corresponding (quasi-)reversible process detected