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Master's Dissertation
DOI
10.11606/D.46.2017.tde-20092017-110950
Document
Author
Full name
Paola Andrea Benavides
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2017
Supervisor
Committee
Araki, Koiti (President)
Bagatin, Izilda Aparecida
Bonacin, Juliano Alves
Title in Portuguese
Efeitos sinérgicos em complexos binucleares de rutênio com um ligante benzobisimidazol em ponte para oxidação da água
Keywords in Portuguese
Catalisador
Complexos Binucleares
Díade Cromóforo-Catalisador
Eletroquímica
Ligante Ponte Funcional
Oxidação de Água
Abstract in Portuguese
Este trabalho está focado no desenvolvimento de complexos de rutênio binucleares baseados no ligante ponte 2,6-bis(2-piridil)benzodiimidazol (dpimH2) com potencial aplicação como catalisadores para oxidação da água. O acoplamento eletrônico entre os centros metálicos bem como as propriedades eletrônicas e catalíticas podem ser controlados via reações ácido-base no ligante bis-bidentado. Dessa forma, neste trabalho descrevemos o preparo e a caracterização do respectivo composto mononuclear, bem como do complexo binuclear simétrico [{RuCl(phtpy)}2(dpimH2)](Otf) 2 (onde phtpy=4-fenil-2,2':6',''-terpiridina), e do análogo assimétrico [{Ru(bpy)2}(dpimH2){Ru(phtpy)Cl}](ClO4)3 (onde bpy=2,2'-bypiridina), que possui um centro catalítico e um grupo cromóforo na mesma molécula como esperado em um fotocatalisador, em que os dois centros catalíticos estão covalentemente conectados através do ligante ponte funcional. As caracterizações estrutural e eletrônica de ambos os complexos por 1H RMN, ESI-MS e espectroscopia de absorção UV-Vis indicaram a presença de isômeros geométricos com perfis eletrônicos similares. Por outro lado, a análise eletroquímica por voltametria cíclica demonstrou menores potenciais Ru(III/II) quando comparados a complexos polipiridínicos análogos. Este potencial redox pode ainda ser catodicamente deslocado através da remoção de prótons dos grupos imidazóis do ligante ponte, possibilitando, dessa forma, a modulação das propriedades eletrônicas e catalíticas destes complexos de rutênio através de reações de protonação/desprotonação dos grupos -NH. Além disso, neste trabalho é investigada a inesperada formação do complexo [Ru(phtpy)2] nas reações do complexo [RuCl3(phtpy)] puro com ligantes bidentados, utilizando-se espectroscopia UV-Vis e de 1H RMN.
Title in English
Synergistic effect in ruthenium complexes bridged by a benzobisimidazole ligand, precursors of water oxidation catalysts
Keywords in English
Benzobisimidazole
Chromophore-catalyst dyad
Dinuclear complexes
Electronic coupling
Water oxidation catalyst
Abstract in English
This work is focused on the development of dinuclear ruthenium complexes with potential application as catalysts for oxidation of water, that are characterized by a benzobisimidazole 2,6-bis(2-pyridyl)benzodiimidazole (dpimH2) bridging ligand, whose interaction between the metal centers as well as the electronic and catalytic properties can be tuned by acid-base reactions in that moiety. Thus, the preparation and characterization of the respective mononuclear species are described. The dinuclear complex [{RuCl(phtpy)}2(dpimH2)](Otf)2(phtpy=4-phenyl-2,2':6',2''-terpiridine), in which two catalytic centers are covalently linked through that bridging ligand, and of the [{Ru(bpy)2}(dpimH2){Ru(phtpy)Cl}](ClO4)3 complex (where bpy=2,2'-bypiridine) integrating a chromophore and a catalytic center in the same molecule as expected for a photocatalyst. The structural and electronic characterization of both complexes by NMR, ESI-MS and UV-vis spectroscopy indicated the presence of geometric isomers with similar electronic profiles. On the other hand, the electrochemical analysis by cyclic voltammetry displayed redox potential values for the Ru3+/Ru2+ couples lower than the respective polypyridyl complex counterparts. This redox potential can be even more shifted to less positive potentials by removal of protons from the imidazole groups in the bridging ligand, opening the possibility of tuning the electronic and catalytic properties of those ruthenium complexes based on protonation/deprotonation of the -NH groups. Furthermore, in this work is analyzed the unexpected formation of the bisterpyridine [Ru(phpy)2] complex in reactions starting with pure [RuCl3(phtpy)] complex with bidentated ligands, as through UV-Vis spectroscopy and RMN.
 
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Publishing Date
2017-09-22
 
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