1.1 Porphyrins - Friedrich-Alexander-Universität Erlangen-Nürnberg

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3 Discussion and Results first reduction potential of a standard tetraarylporphyrin. As one could have expected, the shift should be doubled compared to the one in 53 in respect to non-annulated systems. But that is not at all the case, since also here, the positioning of the exocycles turns out decisive. The lowest shifts are observed for 3 & 17 bis-annulated systems 67 and 69, higher ones for 71 (3 & 7 bis-annulated) and the highest for 68 and 70 being annulated in diagonal fashion (3 & 13). Additionally, not only the reduction potentials themselves are shifted but also their difference ΔE½ Red is affected. While in 67, 69 and 71 the Δ value is approx. 0.36 V, in 68 and 70 only half the value (0.19 V and 0.18 V) is found. Therewith it can be nicely proven, that the setup of analog systems of different symmetries provides a nice tool to fine-tune their electronic properties due to effects on the shapes and coefficients of their frontier orbitals. Table 22. Half-wave potentials E½ given in V versus ferrocene, E(Fc/Fc + ) = +0.53 V, obtained from measurements in CH2Cl2 solution (c = 10 -3 M). For the exact experimental setup see paragraph 6.1, p. 139. 104 Compound E½ Red2 [V] E½ Red1 [V] E½ Ox1 [V] E½ Ox2 [V] 67 -1.15 -0.79 +1.10 +1.38 68 -0.86 -0.67 +1.07 +1.31 69 -1.16 -0.79 +1.10 +1.38 70 -0.85 -0.67 +1.08 +1.31 71 -1.04 -0.69 +1.05 +1.31 53 96 -1.23 -0.95 +1.02 +1.25 15 a,112 -1.45 -1.14 +1.05 +1.35 a literature data on 5,10,15,20-tetraphenylporphyrin (see Scheme 6, p. 7) a 3.2.7.7 Preferential Formation of Certain BCKPs during Synthesis After having discussed the properties of the setup BCKPs, the remainder question, why some of those are preferentially formed during synthesis, shall be clarified. As already mentioned, the 3 & 17 bis-annulation appears favored over the corresponding double ring closure in 3 & 13 fashion by approximately 4 : 1. This could be generally due to electronic and/or steric reasons. Assuming, both annulations take place in a successive manner, the distortional effect of the first exocycle on shape and coefficients of the frontier orbital to be attacked has to be taken into account. A further effect could arise from the paramagnetic metal center by spin delocalization effects as copper(II) complexes were used. Also, the steric impact of the first cyclization could provide a preference as one pyrrolic unit might be deviated from
Discussion and Results 3 planarity in a fashion that brings the carbon atom to be attacked in closer proximity to the reactive site. To get further insight, it was decided to repeat the ring closure with diamagnetic nickel(II) as central metal and to compute possible intermediate structure focusing of their geometry and orbital shapes utilizing the αα-conformer as model. The practical approach resulted in the formation of the corresponding nickel(II) complexes Ni(II)-67 and Ni(II)-68 in comparable overall yield and also comparable product ratio. Thus, any effect of a paramagnetic metal center is negligible and can be excluded from considerations. The theoretical modeling delivered pictorial insights like the one being displayed in Figure 42. 13 ↑ 17 ← Figure 42. Calculated possible intermediate in the bisannulation process with one closed ring (with attached catalyst) on the PM6 level (Spartan® 136 , Materials Studio® 99 ) with displayed shape of the HOMO which is considered to be attacked by the electrophile. Potential annulation sites 13 and 17 are marked by arrows. While the sterics seem to be almost equivalent for both possibly attacked pyrrolic units, the orbital coefficients largely differ as evidently higher electron density is to be found at the favored position 17. Certainly, the calculations on that moderate level cannot serve as absolute proof, but they imply that the reason of the preference is rather found in the changed electronic structure of the intermediate state analog to directing effects also observed in standard bis-functionalization of benzene and other aromatics. 3.2.7.8 Conclusions from the Studies on Bis-Annulated Systems Those compounds nicely demonstrate that not only the choice of specific substituents but also the regiochemical arrangement in a molecule provides an excellent tool to fine-tune the electrochemical and physical properties. In terms of applicability of those compounds for photosensitizing purposes, the performance turned out to not as good as that of 105
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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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3 Discussion and Results Obviously,
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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 6.2.4.9 10 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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