TY - JOUR A1 - Würthner, Frank A1 - Noll, Niklas T1 - A Calix[4]arene‐Based Cyclic Dinuclear Ruthenium Complex for Light‐Driven Catalytic Water Oxidation JF - Chemistry - A European Journal N2 - A cyclic dinuclear ruthenium(bda) (bda: 2,2’‐bipyridine‐6,6’‐dicarboxylate) complex equipped with oligo(ethylene glycol)‐functionalized axial calix[4]arene ligands has been synthesized for homogenous catalytic water oxidation. This novel Ru(bda) macrocycle showed significantly increased catalytic activity in chemical and photocatalytic water oxidation compared to the archetype mononuclear reference [Ru(bda)(pic)\(_2\)]. Kinetic investigations, including kinetic isotope effect studies, disclosed a unimolecular water nucleophilic attack mechanism of this novel dinuclear water oxidation catalyst (WOC) under the involvement of the second coordination sphere. Photocatalytic water oxidation with this cyclic dinuclear Ru complex using [Ru(bpy)\(_3\)]Cl\(_2\) as a standard photosensitizer revealed a turnover frequency of 15.5 s\(^{−1}\) and a turnover number of 460. This so far highest photocatalytic performance reported for a Ru(bda) complex underlines the potential of this water‐soluble WOC for artificial photosynthesis. KW - water KW - oxidation KW - ruthenium KW - dinuclear KW - catalytic KW - artificial photosynthesis KW - homogenous catalysis KW - photocatalysis KW - ruthenium complexes KW - water oxidation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230030 UR - https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202004486 VL - 27 IS - 1 ER - TY - THES A1 - Meza Chincha, Ana Lucia T1 - Catalytic Water Oxidation with Functionalized Ruthenium Macrocycles T1 - Katalytische Wasseroxidation mit funktionalisierten Ruthenium Makrozyklen N2 - In light of the rapidly increasing global demand of energy and the negative effects of climate change, innovative solutions that allow an efficient transition to a carbon-neutral economy are urgently needed. In this context, artificial photosynthesis is emerging as a promising technology to enable the storage of the fluctuating energy of sunlight in chemical bonds of transportable “solar fuels”. Thus, in recent years much efforts have been devoted to the development of robust water oxidation catalysts (WOCs) leading to the discovery of the highly reactive Ru(bda) (bda: 2,2’-bipyridine-6,6’-dicarboxylic acid) catalyst family. The aim of this thesis was the study of chemical and photocatalytic water oxidation with functionalized Ruthenium macrocycles to explore the impact of substituents on molecular properties and catalytic activities of trinuclear macrocyclic Ru(bda) catalysts. A further objective of this thesis comprises the elucidation of factors that influence the light-driven water oxidation process with this novel class of supramolecular WOCs. N2 - Innovative Ansätze zur Ermöglichung eines effizienten Übergangs zur CO2-Neutralität werden angesichts der schnell steigenden Nachfrage nach Energie und der negativen Effekte des Klimawandels dringend gesucht. In diesem Zusammenhang hat das Konzept der künstlichen Photosynthese in den letzten Jahren für besondere Aufmerksamkeit gesorgt. In dieser Hinsicht erscheinen in 2009 erstmals beschriebenen Ru(bda) (bda: 2,2’-bipyridin-6,6’-dicarbonsäure) Wasseroxidationskatalysatoren besonders vielversprechend. Das Ziel dieser Forschungsarbeit war die Untersuchung von funktionalisierten Ruthenium Makrozyklen in der chemischen und photokatalytischen Wasseroxidation, um den Einfluss der Substituenten in den Liganden auf molekulare Eigenschaften und katalytische Aktivitäten der Makrozyklen zu analysieren. Des Weiteren sollten Faktoren identifiziert werden, welche Einfluss auf die Effizienz der Photokatalyse mit dieser neuartigen Klasse von supramolekularen Katalysatoren ausüben. KW - Rutheniumkomplexe KW - Ruthenium complexes KW - Supramolekulare Chemie KW - Katalyse KW - Wasser KW - metallosupramolecular chemistry KW - catalysis KW - water oxidation KW - Oxidation KW - Wasseroxidation KW - Metallosupramolekulare Chemie Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-209620 ER - TY - JOUR A1 - Würthner, Frank A1 - Meza-Chincha, Ana-Lucia A1 - Schindler, Dorothee A1 - Natali, Mirco T1 - Effects of Photosensitizers and Reaction Media on Light‐Driven Water Oxidation with Trinuclear Ruthenium Macrocycles JF - ChemPhotoChem N2 - Photocatalytic water oxidation is a promising process for the production of solar fuels and the elucidation of factors that influence this process is of high significance. Thus, we have studied in detail light‐driven water oxidation with a trinuclear Ru(bda) (bda: 2,2’‐bipyridine‐6,6’‐dicarboxylate) macrocycle MC3 and its highly water soluble derivative m‐CH\(_2\)NMe\(_2\)‐MC3 using a series of ruthenium tris(bipyridine) complexes as photosensitizers under varied reaction conditions. Our investigations showed that the catalytic activities of these Ru macrocycles are significantly affected by the choice of photosensitizer (PS) and reaction media, in addition to buffer concentration, light intensity and concentration of the sensitizer. Our steady‐state and transient spectroscopic studies revealed that the photocatalytic performance of trinuclear Ru(bda) macrocycles is not limited by their intrinsic catalytic activities but rather by the efficiency of photogeneration of oxidant PS\(^+\) and its ability to act as an oxidizing agent to the catalysts as both are strongly dependent on the choice of photosensitizer and the amount of employed organic co‐solvent. KW - photosenitizers KW - water oxidation KW - ruthenium complexes KW - macrocycles KW - trinuclear KW - homogenous catalysis KW - photocatalysis Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-230116 VL - 5 IS - 2 ER - TY - JOUR A1 - Schindler, Dorothee A1 - Meza-Chincha, Anna-Lucia A1 - Roth, Maximilian A1 - Würthner, Frank T1 - Structure-Activity Relationship for Di- up to Tetranuclear Macrocyclic Ruthenium Catalysts in Homogeneous Water Oxidation JF - Chemistry—A European Journal N2 - Two di- and tetranuclear Ru(bda) (bda: 2,2′-bipyridine-6,6′-dicarboxylate) macrocyclic complexes were synthesized and their catalytic activities in chemical and photochemical water oxidation investigated in a comparative manner to our previously reported trinuclear congener. Our studies have shown that the catalytic activities of this homologous series of multinuclear Ru(bda) macrocycles in homogeneous water oxidation are dependent on their size, exhibiting highest efficiencies for the largest tetranuclear catalyst. The turnover frequencies (TOFs) have increased from di- to tetranuclear macrocycles not only per catalyst molecule but more importantly also per Ru unit with TOF of 6 \(^{-1}\) to 8.7 \(^{-1}\) and 10.5 s\(^{-1}\) in chemical and 0.6 s\(^{-1}\) to 3.3 \(^{-1}\) and 5.8 \(^{-1}\) in photochemical water oxidation per Ru unit, respectively. Thus, for the first time, a clear structure–activity relationship could be established for this novel class of macrocyclic water oxidation catalysts. KW - homogeneous catalysis KW - water oxidation KW - ruthenium catalysts KW - renewable fuels KW - metallomacrocycles Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256792 VL - 27 IS - 68 ER -