Ruthenium bipyridyl system

This photoinitiator (or photocatalyst) is composed of an electron relay system in which ruthenium bipyridyl... 

Other workers have employed different sensitiser systems, e.g. duel sensitisation by a zinc porphyrin and copper phthalocyanine on TiOj, Eosin Y or tetrabro-mophenol blue on ZnO, and a ZnO/SnOj mixture with a ruthenium bipyridyl complex, to produce good energy conversion factors. 

Ruthenium bipyridyl complexes are suitable photosensitizers because then-excited states have a long lifetime and the oxidized Ru(III) center has a longterm chemical stability. Therefore, Ru bipyridyl complexes have been studied intensively as photosensitizers for homogeneous photocatalytic reactions and dye-sensitization systems. The Ru bipyridyl complex, bis(2,2 -bipyridine)(2,2 -bipyri-dine-4, 4,-dicarboxylate)ruthenium(II), having carboxyl groups as anchors to the semiconductor surface was synthesized and single-crystal Ti02 photoelectrodes sensitized by this Ru complex were studied in 1979 and 1980 [5,6]. 

Other Semiconductor-Ruthenium Complex Systems. Taqui Khan et al. used a ruthenium(III)-EDTA-bipyridyl complex as a photosensitizer in a Pt-Ti02 semiconductor particulate system [109]. The Ti02 powder was loaded with platinum by the procedure of Erbs et al. [110]. Here 50 mg of the Pt-Ti02 powder was stirred in 10 mL of 0.001 M K[Ru(EDTA)(bipy)] 3 to deposit the ruthenium complex on the Ti02 surface. The 3-treated powder was separated by centrifugation and dried at room temperature. 

Scheme 7.2.17 contains another very interesting bipyridyl system, namely the ruthenium(II) complex of 2,2 -bipyridine. In this complex the d-orbitals of the ruthenium ion and the 7t-orbitals of the bipyridine are similar in energy and mix. As a result, there is almost no redox quenching of the excited singlet and triplet states and the compound fluoresces strongly, which is very unusual for a transition metal complex. It cannot only be used to produce hydrogen with the aid of viologen, but the oxidation product ruthenium(III) bipyridinate is such a... 

The theme of photosensitizing semiconductor electrodes introduced in Section 57.3.2.5(iii) may be developed with an example from ruthenium-bipyridyl chemistry. The sequence (40) is well known. The effectiveness of the photosensitization should be increased by the covalent attachment of the tris(bipyridyl)ruthenium(II) entity to the semiconductor surface, for example to Sn02- This has been achieved using the versatile halosilane chemistry shown in equation (41). The counter anion was PFg . Cyclic voltammetry showed that the behaviour of the systems Sn02/aqueous [Ru(bipy)3]2 and Sn02(film)/electrolyte were very similar but with a +0.05 V shift in E°. The coated electrode gives a photocurrent with a red shift of 10 nm which is twice as large as for the non-coated electrode. Unfortunately the current falls off due to promotion of the hydrolysis of the film. 

Photocurrent generation is one of the most interesting direct applications of photosynthetic studies. The adsorption of sensitizers onto semiconductor surfaces has been found to be an efficient way to generate photocurrents and has been studied extensively. Ruthenium bipyridyl complexes, in particular, have been the focus of recent research [137-139]. In these cases, only the first layer of molecules, which is in direct contact with the surface, is active. A highly porous semiconductor material was therefore employed to compensate for the low level of absorption of the single molecular layer. Other varieties of chromophores, semiconductor materials, and electron carriers for totally solid systems have been the subjects of extensive studies. The present... 

A photoactive metal center is introduced in these systems. The ruthenium bipyridyl complexes are coordinated to the emeraldine base to form the corresponding polymer complexes as described above." The incorporation of the ruthenium centers to the pyridyl backbone has been also reported to give the ruthenium complexes Conjugated ruthenium bipyridine complexes thus obtained are evaluated to be photorefractive materials. Other transition metal complexes can be employed to form the corresponding polymer complexes. The pyridine unit is replaced by bithienyl, 1,4-diazabutadiene, ethylene, benzimidazole or thiazole. ... 

As chemists have become more sophisticated in their ability to design and understand chemical oscillators, and as they have increasingly sought systems that are relevant to biological processes, oscillatoiy systems with feedback have become an area of growing interest. We describe here experiments (13) and computer simulations (14) on a photosensitive variant of the BZ reaction, in which the catalyst is a ruthenium bipyridyl complex, Ru(bpy)3 (15). 

In a series of papers, heated indium tin oxide (ITO) electrodes were proposed as carriers for electrochemiluminescent sensors of diverse analytes [70-74]. The system couples the advantages of a heated electrode with the optical transparency property of ITO glass. In [70], H2O2/MCLA and TPrA/Ru(bpy)3 have been used to test the arrangement which was constructed very similar to the scheme given in Fig. 6.15. In [71], TPrA and colchicine were detected in human serum by means of the ruthenium bipyridyle ECL system. Immobilised xanthine oxidase as a sensor system for hypoxanthine has been mentioned already. It has been used also with a heated ITO electrode [72]. Further examples for electrochemiluminescence detection with heated ITO electrodes were the analysis of Ns-methyladenosine in urine... 

Abruna HD, Bard AJ (1982) Electrogenerated chemiluminescence. 40. A chemiluminescent polymer based on the tris(4-vinyl-4 -methyl-2,2 -bipyridyl)ruthenium(II) system. J Am Chem Soc 104 2641-2642... 

A dye which shows particular promise for this application is the octahedral ruthenium(n) complex of 2,2 -bipyridyl (234). While this type of system appears to offer considerable potential as a means of solar energy conversion, the efficiency of the technology, at its current state of development, is significantly lower than that of traditional silicon photocells. 

In a very special system, the photoelectrochemical regeneration of NAD(P)+ has been performed and applied to the oxidation of the model system cyclohexanol using the enzymes HLADH and TBADH. In this case, tris(2,2 -bipyridyl)ruthenium(II) is photochemically excited by visible light [43]. The excited Ru(II) complex acts as electron donor for AT,AT -dimethyl-4,4 -bipyridinium sulfate (MV2+) forming tris(2,2 -bipyridyl)ruthenium(III) and the MV-cation radical. The Ru(III) complex oxidizes NAD(P)H effectively thus... 

Metal-to-hgand charge transfer (MLCT) systems are mostly based upon complexes of ruthenium and rhenium. The simplest and best known example of a MLCT lumophore is tris(2,2 -bipyridyl)ruthenium(ii) where photon absorption leads to an excited state composed of a centre and a radical anion on one of the bipyridyl units. 

ILs have been used in the CE-electrochemiluminescence (ECL) method to determine bioactive constituents in Chinese traditional medicine [58]. CE/Tris(2,2-bipyridyl) ruthenium(II) (Ru(bpy)3 +) ECL, CE-ECL, with an IL detection system was established to determine bioactive constituents in Chinese traditional medicine opium poppy, which contains large amounts of coexistent substances. Running buffer containing 25 mM borax-8 mM [C2CiIm][BF4] (pH 9.18) was used, which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Quantitative analysis of four alkaloids was... 

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