Binuclear Ruthenium(Ⅱ) Tris-bipyridine Complexes: Synthesis And Electrogenerated Chemiluminescence Property

Electrogenerated chemiluminescence (ECL) is the luminescence generated during anelectrochemically initiated reaction, which involves the generation of species at electrodesurfaces that then undergo electron-transfer reactions to form excited states that emit light.ECL can be used for detection of molecules and many applications have been found inchemical analysis, environment and clinical immunoassays. However, only the complexbased on ruthenium tris(bipyridine) [Ru(bpy)₃²⁺] is one of the most widely used ECL-activeinorganic molecules. In this thesis we described the design and synthesis of two kinds ofbinuclear ruthenium(â…¡) tris(bipyridine) complexes for the purpose of increasing ECLintensity by alternating different bridges between two metal centers.Firstly, we designed and synthesized three aryl diamide centered binuclear ruthenium(â…¡)tris(bipyridine) complexes (aryl: benzene, biphenyl and naphthalene). Their photophysical,electrochemical and ECL properties have been investigated. All the three binuclearruthenium(â…¡) complexes have similar photophysical and electrochemical properties but showdifferent ECL behaviors. The binuclear ruthenium(â…¡) complex with naphthalene diamidebridge has the best ECL property and its intensity is 10 times higher than that of referencecompound Ru(bpy)₃²⁺, which is by far the first report on such a good ECL property. Thiscompound could become one of the best potential candidates in analytical applications.Secondly, we designed and synthesized two binuclear ruthenium(â…¡) tris(bipyridine)complexes and three mononuclear complexes with bipyridine-cappedoligothiophene-2-yl-vinyl ligands by Wittig or Wittig-Hornor reactions. Their photophysics,electrochemistry and ECL properities were studied. For mononuclear complexes, UV-visabsorption spectra show a significant red shift both at ³MLCT and atÏ€-Ï€^* transition of thebridged ligands with the increase of the number of thiophene-2-yl-vinyl unit. For thebinuclear complexes these two absorption bands are overlapped. All of the rutheniumcomplexes exhibit very weak emission compared to that of reference Ru(bpy)₃²⁺. All themetal complexes have similar oxidation, the second and the third reduction potentials, butthey have different first reduction potentials. For RuTRu the interaction between two metalcenters is very weak and for Ru2TRu the interaction is much weaker. ECL of all metalcomplexes are recorded without adding any reductant or oxidant. For binuclear rutheniumcomplexes ECL intensity decreased dramatically with the increase in the number of thiophene-2-yl-vinyl. While for the monometallic complexes ECL intensity strongtened. TheECL intensity of all the five ruthenium complexes follows in the order: RuTRu＞Ru3T＞Ru2T＞RuT＞Ru2TRu, inferior to that of the reference Ru(bpy)₃²⁺ under the sameconditions, The possible reason is that ligands are easier to obtain electron because of theelectron-withdrawing effect of the oligothiophene-2-yl-vinyl according to the first reductionpotentials, and ruthenium(â…¡) is more difficult to be reduced to ruthenium(â… ) relatively. Thusannihilation reaction occurs with difficulty and relative ECL intensity is very weak. Themechanism of ECL is also deduced.Additionally, a mixed-valence binuclear ruthenium complex with pyridine and phenolligands ([Ru₂(bpmp)(O-ptby)₂](ClO₄)₂, Ru₂BMPB) has been synthesized and itsspectroelectrochemistry property has been investigated. The Ru₂^{â…¡,â…¢} complex undergoesreversible redox process. Visible to NIR spectra can be changed by controlled potentialsbecause of the electronic transferring on ruthenium, which exhibited controllable switchperformance in the Vis to NIR region.