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| Author(s): |
Reginaldo César Rocha
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2000-12-01 |
| Examining board members: |
Henrique Eisi Toma;
Gianluca Camillo Azzellini;
Alzir Azevedo Batista;
Neyde Yukie Murakami Iha;
Luiz Antonio Andrade de Oliveira
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| Advisor: | Henrique Eisi Toma |
| Abstract | |
The chemistry of a series of binuclear ruthenium(III/II) and iron(III/II) complexes with N-heterocyclic ligands was studied. The [RuIII,II(edta)-2-, [RuIII,II(NH3)5]3+,2+, [RuIII,IICl(bpy)2]2+,+ and [FeIII,II(CN)5]2-,3- metal ions were specifically employed as the terminal moieties, and benzotriazole or benzimidazole and their anionic derivatives as the bridging ligands. Symmetric, Ma-L-Ma, and asymmetric, Ma-L-Mb, systems were synthesized and characterized in aqueous or organic solutions by means of conventional spectroscopy and electrochemical techniques. Special emphasis was devoted to the intervalence properties associated with the mixed-valence complexes. In addition, the application of ET theoretical models was largely stressed as useful tools to explain the photoinduced intramolecular ET processes (i.e., intervalence transfer) in valence-trapped and partially or fully delocalized systems. In order to rationalize the properties of the binuclear complexes, a detailed investigation of the starting mononuclear complexes was carried out from the point of view of their reactivity and redox chemistry. In this case, two issues of major interest were deeply taken into account: linkage isomerism (in the particular examples involving the benzotriazole derivatives) and proton-coupled electron transfer reactions in aqueous solutions. Knowledge acquired from the characterization of the monomer metal units made the study of larger molecules possible. In this way, extended structures like \"molecular wires\" were designed by using the same N-heterocyclic spacers and metal moieties, resulting in trinuclear species of the type Ma-L-Mb,-L-Ma, which displayed remarkable electronic communication between the metal units through the conductor bridge. Advances were also reached following the pH effects on electronic interactions of mixed-valent species. Protonation /deprotonation of the bridging ligand, for instance, revealed a pronounced proton-induced \"on/off\' molecular switching on the metal-metal coupling and electron delocalization of such species. This example of molecular devices provided an outstanding model within the search for compounds with potential usefulness in molecular electronics and/or nanotechnology, whose conception embraces the development of supramolecular systems, an approach that has long been pursued within the research scopes in the laboratory where the current work was developed. (AU) | |