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|3.3 NN-NHC-Ligand bbip: Toward Second Generation Catalysts| Table 14: UV/vis absorption and emission data of Ru(bbip), Ru(bbip)Ag, Ru(bbip)Pd, Ru(bbip)Rh and [Ru(tbbpy) 3 ] 2+ measured in deaerated acetonitrile at room temperature. Complex Solvent λ max, abs λ shoulder, abs λ max, em Φ a τ τ a,b τ a,c [nm] [nm] [nm] [ns] [ns] [ns] [Ru(tbbpy) 3 ] 2+[90] ACN 458 433 613 107 730 DCM 461 437 604 248 610 Ru(phen) [108, 125] ACN 454 431 610 211 1 400 DCM 455 602 0.03 272 Ru(ip) ACN 460 431 616 DCM 460 431 604 [Ru(ip)(bpy) 2 ] 2+[192] ACN 453 425 623 0.14 150 726 [Ru(ip)(phen) 2 ] 2+[194] DCM 451 570 Ru(bip) ACN 460 429 618 DCM 462 429 608 Ru(bbip) ACN 435 481 663 0.26 192 920 1 000 DCM 440 473 654 556 1 300 Ru(bbip)Ag ACN 440 474 646 0.34 (183) 1 450 DCM 449 473 625 (404) 1 400 Ru(bbip)Pd ACN 440 475 646 0.39 1 100 1 000 DCM 471 441 620 1 400 Ru(bbip)Rh ACN 440 473 625 0.17 430 DCM 471 441 620 900 a oxygen free, b emission experiments, b transient absorption experiments a small deviation in acetonitrile (λ M = Rh em, ACN ≈ 625 nm). These intermediate emission wavelengths represent the influence of the phenanthroline fused NHC moiety on energy of the 3 MLCTemission involving LUMO ( ̂LL)s in bbip. Seemingly, this differs from the 1 MLCT-absorption involved LUMO ( ̂LL) as they are relatively unperturbed by the change of the nature of the second sphere. This observation is very similar to the findings of the tpphz and dppz containing complexes (see discussion in chapter 1.10.1 on page 42 ff.). Based on this similarity, it can be assumed that a (phenanthroline)/bipyridine centered π*-orbital (LUMO (bpy) ) and a (benz)imidazole centered π*- orbital (LUMO (im) ) exists in such complexes. Furthermore, it can be speculated that the LUMO (bpy) is mainly involved in the absorption process and that is is only little influenced by the imidazole (all |143|
|3.3 NN-NHC-Ligand bbip: Toward Second Generation Catalysts| absorption bands, ranging from Ru(ip) to Ru(bbip)Pd, are rather similar to [Ru(bpy) 3 ] 2+ ) while the strongly imidazole-influenced LUMO (im) is mainly involved in the emission of Ru(bbip) and the Ru(bbip)M complexes, as strong shifts of the emission were observed (see figure 102). In these later two cases a significant degree of carbene character can be assigned to the imidazole moiety. N N N 2+ N Ru N N R N N N N N 2+ N Ru N N R N N R N N N 2+ N Ru N N R N N R M Ru(ip) / Ru(bip) Ru(bbip) Ru(bbip)M Figure 102: Representation of the proposed LUMO ( ̂LL) -situation in the complexes with ip-derived ligands. The 1 MLCT-absorption involved bipyridine centered LUMO (bpy) is depicted in orange, the higher lying (benz)imidazole LUMO (im) in ip is denoted in red and the lower lying LUMO (im) in Ru(bbip) and Ru(bbim)M complexes are denoted in green and blue. All observations in the Ru(bbip)M complexes can be explained by the decreased +M and -I effect in the carbene complexes. In detail, a stepwise increase of the π-character of the carbene carbon and a stepwise decrease of the π-delocalization on the imidazole rings can be expected with respect to the starting imidazole Ru(bip) and transformation into the imidazolium salt Ru(bbip) and subsequent carbene complex formation. According to the bathochromically shifted emission in Ru(bbip)M complexes with respect to the Ru(ip)-type complexes a localization (storage) of the excited electron on the bridge, in particular in the imidazole-centered orbital near the second metal can be expected. Thus, a positive effects on the application of the Ru(bbip)M-type complexes in reduction catalysis can be proposed. Finally, quantum yields were determined in acetonitrile and dichloromethane. The emission quantum yields follow the tendency: Φ (M = Pd) = 0.39 > Φ (M = Ag) = 0.34 > Φ (M = f) = 0.26 > Φ (M = Rh) = 0.17 in oxygen free acetonitrile. In dichloromethane ordering of the relative emission intensities are different (Ag > Rh > f > Pd), which might be assigned to impurities such as oxygen in the palladium sample or the formation of a dimeric complex, which exhibits an unexpected low emission intensity. Still, even for the weakest emitting new complex a significantly higher quantum yield emerges relative to that reported for the parent complex [Ru(bpy) 3 ] 2+ . In short, |144|
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Development of Novel Catalysts for
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Diese Arbeit entstand auf Anregung
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Den Arbeisgruppen von Prof. Dr. U.
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Contents 1 Introduction 1 1.1 Fossi
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|Contents| 6 Experimental Section 1
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|1 Introduction| 1 Introduction The
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|1.1 Fossil Fuels and Nuclear Power
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|1.2 Renewable Fuels| of natural ga
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|1.3 Energy Transformation and Stor
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|1.4 Solar Energy Conversion| A fra
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|1.5 Photosynthesis| Figure 9: Mole
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|1.6 Photocatalyzed Reactions| 2 NA
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|1.6 Photocatalyzed Reactions| (1)
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|1.7 Mimicking Photosynthesis| So t
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|1.8 Formalisms of Photocatalytic S
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|1.9 Multicomponent Systems from Fu
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|1.10 Intramolecular Photoredoxcata
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|2 Scope of the Thesis| motifs with
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|3.1 Brominated Phenanthrolines - A
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|3.2 Bisphenanthroline: A Suitable
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Page 170 and 171: |3.4 Outlook, Exploratory Investiga
Page 185 and 186: |4 Summary| 4 Summary Against the b
Page 187 and 188: |4 Summary| The resulting complexes
Page 189 and 190: |4 Summary| 10 [TEA] + TEA visible
Page 191 and 192: |4 Summary| absorption between 430
Page 193 and 194: |4 Summary| additional NN- and NHC-
Page 195 and 196: |5 Zusammenfassung| Die Herstellung
Page 197 and 198: |5 Zusammenfassung| phenphen und Ru
Page 199 and 200: |5 Zusammenfassung| Fragment tragen
Page 201 and 202: |5 Zusammenfassung| [TEA] + TEA vis
Page 203 and 204: |5 Zusammenfassung| In einer abschl
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|6 Experimental Section| Spectroele
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|6 Experimental Section| 1.3648 was
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|6.1 Synthesis of the Organic Ligan
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|6.2 Synthesis of the Metal Complex
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|7 Appendix| 7 Appendix dd ddd DEI
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|7 Appendix| Ru(tpphz)Os [Ru(bpy) 2
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|References| [26] M. Chanon, M. Sch
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|References| [81] S. Tschierlei, M.
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|References| [138] L. Pazderski, J.
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|References| [194] C. Liu, J. Li, B
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Selbstständigkeitserklärung: Ich
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