1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

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3 Discussion and Results Time-resolved experiments show a mono-exponential decay of the first excited singlet state in each case compared to bis-exponential decays for mono-exocyclic systems 53, 57 and 58. That is not surprising since the effect is due to the presence of distinguishable tautomers in the mono-exocyclic compounds having the NH-protons situated on opposite lying nitrogen atoms. In all bis-exocyclic systems, those positionings are equivalent and thus only one major tautomer is to be observed. Like for the mono-exocyclic compounds, also here the determined fluorescence quantum yields (Φfl) are quite low. The quantum yields for intersystem crossing (ΦISC) vary between 0.46 and 0.68 and are therewith significantly lower than for 53 (ΦISC = 0.88). Thus, the spin- orbit coupling seems to be significantly lowered in efficiency by the bis-annulation process itself and it appears furthermore affected by the regiochemistry. The same applies for the capability of 1 O2 generation. The values are thereby highest for 67 and 69, followed by those for 68 and 70 ending up at the lowest ones for 71. This can be seen as the consequence of an also influenced efficiency of the energy transfer between a BCKP in its triplet state (T1) and dissolved oxygen in the sample, ηET(T1→ 3 O2). The corresponding values are determined close to 1 for 67 and 69 (and therewith comparable to 53) but else significantly lower (down to 0.57 for 71, in the worst case). The underlying data is gathered in Table 21. Table 21. Photophysical parameters for 67-71 in DMF: quantum yield of fluorescence (Φfl) and fluorescence decay time τfl, quantum yield for intersystem crossing (ΦISC), singlet oxygen quantum yield (ΦΔ) and estimated efficiency of energy transfer ηET from the triplet sensitizer to triplet oxygen. 102 Compound Φfl a,b τfl [ns] a ΦISC c ΦΔ d ηET(T1→ 3 O2) 67 0.016 0.83 0.68 0.65 0.96 68 0.03 1.48 0.63 0.52 0.83 69 0.016 0.83 0.68 0.62 0.91 70 0.035 1.49 0.67 0.52 0.78 71 0.02 0.73 0.46 0.26 0.57 a excitation at 532 nm a b reference used: 5,10,15,20-tetraphenylporphyrin 15 (Φfl = 0.11) 87 c estimated by ps-transient absorption spectroscopy technique d reference used: 5,10,15,20-tetraphenylporphyrin 15 (ΦΔ = 0.65) 88
3.2.7.6 Cyclic Voltammetry Discussion and Results 3 Compounds 67-71 were investigated under the same conditions as the mono-exocyclic ones 53-58 (see paragraph 3.2.3.5). The obtained voltammograms are depicted in Figure 41. -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.6 0.8 1.0 1.2 1.4 E [V] Figure 41. Cyclic voltammograms of 67 (almost identical to 69), 68 (almost identical to 70) and 71 measured in CH2Cl2 solution (c = 10 -3 M) vs. ferrocene, E(Fc/Fc + = +0.53 V), as internal standard. For further experimental details see paragraph 6.1, p. 139. For the interpretation, the data have to been seen in comparison to those for 53 as corresponding mono-annulated system on also to non-functionalized porphyrin 15 representing a standard tetraphenylporphyrin systems of that kind. The corresponding 5 μA 67 (69) 68 (70) 71 values for the obtained half-wave potentials are summarized in Table 22. Concerning the anodic regions of the voltammograms, the oxidation potentials of the BCKPs appear well comparable to standard porphyrins like 15 and also to mono-exocyclic system 53. Thus, also the presence of two electron withdrawing ketone groups seems to have no effect on the oxidability of the porphyrin core. In contrast, the attachment of a second ketone does clearly affect the cathodic region since the reductions steps are observed at very high potentials, meaning an ease of reduction. The shift is that drastic compared to 15 that in all these systems both reductions are mostly completed at potentials higher than the 103
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Semi-Natural and Synthetic Chiral C
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Die vorliegende Arbeit entstand in
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Table of Contents 1 Introduction 1
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n J j-coupling (constant) with n in
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1 Introduction characteristics. For
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1 Introduction 1.1 Porphyrins - A G
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1 Introduction Especially interesti
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1 Introduction 8 [H] 4 + 4 O H O H
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1 Introduction complexes are usuall
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1 Introduction transitions as it is
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1 Introduction 1.2 Photodynamic The
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1 Introduction Certainly, Photofrin
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1 Introduction intact membranes bei
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1 Introduction components, the limi
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2 State of The Art & Aims They were
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2 State of The Art & Aims 2.2 Aim o
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3 Discussion and Results encapsulat
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3 Discussion and Results diastereot
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3 Discussion and Results 30 E ½ Re
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3 Discussion and Results irradiatio
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3 Discussion and Results 34 R 1 O N
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3 Discussion and Results 3.2.2.1.2
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3 Discussion and Results Table 4. S
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3 Discussion and Results 3.2.2.2 FR
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3 Discussion and Results 3.2.2.3 Ac
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3 Discussion and Results 3.2.3.1 IR
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3 Discussion and Results 3.2.3.2 NM
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3 Discussion and Results 3.2.3.3 Va
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3 Discussion and Results 3.2.3.3.2
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Page 140 and 141: 4 Summary As the characterization d
Page 142 and 143: 5 Zusammenfassung 5 Zusammenfassung
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6 Experimental Section 6.2.4.7 5 4
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6 Experimental Section 6.2.4.11 10
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6 Experimental Section EA: C57H56N4
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6 Experimental Section 6.2.4.15 10
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6 Experimental Section 6.2.5 A2B2-T
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6 Experimental Section 6.2.5.5 αβ
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6 Experimental Section 6.2.5.7 αβ
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6 Experimental Section 6.2.5.9 αα
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6 Experimental Section 6.2.5.11 α
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6 Experimental Section 6.2.5.13 α
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6 Experimental Section 6.2.6 AB2C-T
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6 Experimental Section UV/Vis (CH2C
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6 Experimental Section UV/Vis (CH2C
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6 Experimental Section broad signal
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7 References 16 H. Fischer, K. Zeil
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7 References 57 S. Schwartz, K. Abs
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7 References 89 (a) R. C. Fuson, J.
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7 References 131 (a) J. Perdew, Phy
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S. Jasinski, N. Jux, “Investigati
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Ein großer Dank gilt auch den Ange
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Cirruculum vitae Stefan Jasinski Ge
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1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

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