Design,Synthesis And Properties Of Catalysts For Water Oxidation Based On Half-sandwich Ir,Rh And Ru Motifs

The development of new catalysts for water oxidation has become one of the hottest topics in the artificial mimic solar energy field, due to the difficult condition for water oxidation reaction to happen. In this test, the ability of compounds based on half-sandwich iridium/ruthenium was exhibited in catalyzing water oxidation reaction. The structures of compounds is the metal bridged with organic ligands?including azo-dye ligands and pyridine-substituted 8-hydroxyquinoline ligands? were also described in this test. A central metal with stable electronic environment and high activity was realized by design of the organic ligands and was more suitable to be a catalysis for water oxidation. The main part of this paper includes the following four aspects:1. The molecular structures and electronic properties of new ionic, hydrophic,half-sandwich complexes of the formula [?⁵-Cp^*Rh?L??Me OH?] and [?⁶-CyRu?L??H₂O?],where L is azo-dye compound of p-(2-Hydroxy^-1-naphthylazo) benzenesulfonic acid sodium salt, were characterized. The results of electrochemical studies showed these complexes have potential electronic properties for using as water oxidation catalysts potentially.2. The molecular structures and electronic properties of new ionic, hydrophic,half-sandwich complexes of the formula [?⁵-Cp^*Ir?L??Cl?]?OTf?, [?⁵-Cp^*Rh?L??Cl?]?OTf?,[?⁵-Cp^*Ir?L??H₂O?]?OTf?₂ and [?⁵-Cp^*Rh?L??H₂O?]?OTf?₂, where L is1-?2-Pyridylazo?-2-naphthol were characterized. The results of electrochemical studies showed these complexes have potential electronic properties for using as water oxidation catalysts. Interestingly, all of their solutions color were transformed from brown to green unambiguously under a pH=12 environment. For the reason that they have properties to be pH sensors.3. Novel binuclear [?⁶-CyRu?L?]₂?OTf?₂ and tetranuclear [?⁶-CyRu?L?]₄?NO₃?₄metallacycles were prepared by treating pyridyl-substituted 8-hydroxyquinoline ligand[?E?-2-?2-?pyridin-3-yl?vinyl?quinolin-8-ol]?HL? with [?p-Cy?Ru??-Cl?Cl]₂ with the presence of AgOTf or AgNO3. Molecular structures of complexes were confirmed by single crystal X-ray diffraction, revealing that both of them have marcocycle frameworks induced by counter anions OTf- and NO3-, respectively. The electrochemical properties oftwo metallacycles were investigated by Cyclic Voltammograms?CVs?, showing that they have great potential properties as catalysts for water oxidation. Good efficiency was obtained by utilizing complex [?⁶-CyRu?L?]₄?NO₃?₄ as water oxidation catalyst with the presence of Ce??? salt as an oxidant at a high pH value.4. New tetranuclear macrocycles [Cp^*Ir?L?]₄?OTf?₄ and [Cp^*Rh?L?]₄?OTf?₄ were successfully synthesized by treating pyridyl-substituted ligand3-?Pyridin-3-ylazo?-naphthalen-2-ol?HL? with [Cp^*M??-Cl?Cl]₂?M = Ir, Rh? with the presence of AgOTf and their structures were characterized by EA, IR and NMR, to confirm their elementary components and frameworks. For further classify their molecular structures, single crystal X-ray diffraction were performed on suitable crystals. The results showed both of them have tetranuclear macrocyclic structures. Cyclic voltammograms?CVs? were carried out to investigate electrochemical properties of [Cp^*Ir?L?]₄?OTf?₄,suggesting that it has great potential application as catalysts for water oxidation. Hence,complex [Cp^*Ir?L?]₄?OTf?₄ was used as a catalyst for water oxidation with the presence of electronic sacrificial agent, obtained a good efficiency which reached up to 2.47min^-1.These results indicated that half-sandwich iridium, rhodium, ruthenium organometallic complexes have huge potential properties in catalyzing water oxidation and they provide more experimental and theoretical basis for the development of solar energy through artificial photosynthesis structure.