Ru-bipyridyl complexes

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]. 

Ru-(bipyridyl) complex that acts as a molecular switch ... 

Hagfeldt and coworkers reported the oxidative electropolymerization of styryl-substituted Ru bipyridyl complexes, including 8, designed to act as new sensitizer dyes in Gratzel-type cells. In contrast to other polymers, the 2max of the polymer actually blue-... 

In conforming to an expected linear free energy relationship, the Ce(lV) oxidation of various 1,10-phenanthroline and bipyridyl complexes of Ru(II) in 0.5 M sulphuric acid are consistent with the requirements of the Marcus treatment . The results for the oxidation of the 3- and 5-sulphonic-substituted ferroin complexes by Ce(IV) suggest that the ligand does not function as an electron mediator, and that the mechanism is outer-sphere in type. Second-order rate coefficients for the oxidation of Ru(phen)j, Ru(bipy)3, and Ru(terpy)3 are 5.8x10, 8,8 X 10, and 7.0 x 10 l.mole . sec, respectively, in 0.5 M H2SO4 at 25 °C a rapid-mixing device was employed. 

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... 

Ru(0)3(phen)]j0 and Ru(0) (bpy).3Hj0 These formulae were proposed for the products of reaction of RuO with 1,10-phenanthroline (phen) or 2,2 -bipyridyl (bpy) in CCl They are diamagnetic, and their electronic and IR spectra were measured [444, 445], With methanol they give a variety of Ru(VI) and Ru(TV) complexes [444], By analogy with Ru(0) (py)j , though, they may be better formulated as Ru2(0)g(L)2 (L=bpy, phen). 

A reversible one-electron transfer at + 1.34 V was observed, assigned to the metal-centered Ru(II)/Ru(III) oxidation. The complex cathodic pattern of this species, comprising 10 successive reversible one-electron transfer, is the sum of that of its two subunits, the C60 core and the Ru(II) tris-bipyridyl complex, thus excluding any... 

Reducing agents, such as hydroquinone, Br , I, SCN- ions, and others, are used as supersensitizers for electron photoinjection reactions. Figure 28 illustrates how an admixture of hydroquinone affects photocurrent in the system CdS—rhodamine B. In certain cases the solvent, water, can also act as a supersensitizer. For example, if the bipyridyl complex of Ru(II) is a sensitizer, the oxidized form, the complex of Ru(III), can oxidize water to oxygen... 

The polystyrene-pendant Ru(bpy) + complex has been likewise obtained by the reaction of dichloro-bis(2,2 -bipyridyl-Ru(II)) complex with bipyridylated polystyrene [16] (Fig. 8). 

Ruthenium(II) bipyridyl and Cr(III) aquo complexes luminesce strongly when photostimulated. The emission of light can be quenched effectively by such species as oxygen, paraquat, Fe(II) aquo complexes, Ru(II) complexes and Cr(NCS)i (Sutin [15]). Pfeil [16] found that the quenching rate coefficients are typically a third to a half of the value which might be predicted from the Smoluchowski theory [3]. 

Using a different approach, Lieberman and Sasaki [40] described the formation of a well-defined triple helix structure by the self-assembly of three peptide segments (47) via the formation of an iron (II) bipyridyl complex (Fig. 17). Independently, Ghadiri and Case [41] also reported the preparation of a triple helix structure using a similar strategy with peptide 48. In this case, the template is formed by the coordination of Ni(II), Co(II), or Ru(II) with three bipyridine units. The triple helix structure with Ru(II) was characterized by mass spectrometry. Furthermore, CD studies showed an increase in helicity and structural stability. By a clever modification, the same authors used the self-... 

In an elegant self-assembling system based on the use of cyclodextrin hosts, DeCola and coworkers noncovalently linked an alkylcarboxyan-thracene to an a-cyclodextrin bearing Ru(II) complex that also had an Os(II) bipyridyl derivative attached via noncovalent interaction with a -cyclo-dextrin substituent on the Ru complex (Fig. 14). The system yields an energy transfer cascade from the photoexcited anthracene to the Ru to bpy 3 MLCT state, which in turn transfers energy to the Os(II) complex 3MLCT state. All rate constants are > 108 s-1 [88]. 

The ruthenium complex Cp Ru(bipyridyl)Cl has been developed as a catalyst for the first regioselective tandem Michael addition-allylic alkylation of activated Michael acceptors. The net outcome is the decarboxylative insertion of Michael acceptors into allyl /3-keto esters to produce (215). The reaction combines the generation of Ru-tt-allyl and enolate from (213) the enolate is first added to the Michael acceptor (214) and the resulting species is captured by the Ru-tt-allyl.254... 

Schlicke et al. [27] synthesized rod-like compounds, in which two metal-bipyridyl complexes were linked by >/igo(plienylene)s. The longest spacer (seven phenylene units) gave rise to a metal-to-metal distance of 4.2 nm. In this work, Dexter-type energy-transfer mechanism from [Ru(bpy)3]2+ to [Os(bpy)3]2+ was established. The energy transfer mechanism is essentially temperature-dependent and decreases exponentially with an attenuation coefficient of 0.32 A-1. 

Interest continues in pyrazine-bridged polymeric ruthenium complexes. Following an earlier communication,48 further details have been given of a general synthetic route to pyrazine-bridged Ru11 bipyridyl complexes (equations 10 and ll).49 Employing the reaction of Ru—N02 complexes to yield Ru—NO, in combination with the... 

A special technique was employed by Naka et al. for the preparation of A2B stars, A being PEO and B polyoxazoline (POX) [26] according to Scheme 8. Ru(III) complexes with bipyridyl terminated polymers were utilized in this method. Characterization data were not provided for these miktoarm star copolymers. 

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