Ru -tris-bipyridine

Steiner s group [5] measured MFEs on photooxidation quantum yields of Ru -tris(bipyridine) type complexes (RuL3 ) in water at room temperature with a Bitter type magnet at the High Magnetic Field Laboratory of MPI/CNRS at Grenoble. Their reactions occur as follows ... 

A good example is the excited state of the tris(bipyridine)ruthenium(2+) ion, Ru(bpy)5+. This species results from the transfer of an electron from the metal to a ligand. In the language of localized valences, it is a ruthenium(3+) ion, coordinated to two bipyridines and to one bipyridyl radical anion in other words, [Ru3+(bpy)2(bpy )]2+. This excited state is a powerful electron donor and acceptor.17 The following equations show an example of each quenching mode ... 

Supramolecular Ru and/or Os complexes of tris(bipyridine) bridging ligands. Syntheses, absorption spectra, luminescence properties, electrochemical behavior, intercomponent energy, and electron transfer. [P. Belser, A. von Zelewsky, M. Frank, C. Seel, F. Vogtle, L. De Cola, F. Barigelletti, V. Balzani, J. Am. Chem. Soc. 1993, 225(10), 4076-4086] [ 23]. 

Photocatalytic enantioselective oxidative arylic coupling reactions have been investigated by two different groups. Both studies involved the use of ruthenium-based photocatalysts [142, 143]. In 1993, Hamada and co-workers introduced a photostable chiral ruthenium tris(bipyridine)-type complex (A-[Ru(menbpy)3]2+) 210 possessing high redox ability [143]. The catalytic cycle also employed Co(acac)3 211 to assist in the generation of the active (A-[Ru(menbpy)3]3+) species 212. The authors suggested that the enantioselection observed upon binaphthol formation was the result of a faster formation of the (R)-enantiomer from the intermediate 213 (second oxidation and/or proton loss), albeit only to a rather low extent (ee 16 %) (Scheme 54). 

Huang P, Magnuson A, Lomoth R, et al. Photoinduced oxidation of a dinuclear Mn2(II,II) complex to the Mn2(III,IV) state by inner and intramolecular electron transfer to Ru(III) tris-bipyridine. J Inorg Biochem 2002 91 159-72. 

Encapsulation of a Ru atom into a caged [109, 110] or hemicaged [299] tris-bipyridine ligand extends the MLCT excited state lifetime and improves photostability relative to [Ru(bpy)3] ", while retaining the fast (diffusion controlled) bimolecular excited state electron transfer reactivity. In contrast, the [Ru(bpy)3] + in the core of a dendrimer [248] has about the same inherent lifetime as the free complex but the rate of electron transfer quenching rapidly decreases with increasing the number and size of dendrimer branches. 

Ru(II)tris(bipyridine) [Ru(bpy)3 +] as a photosensitizer, triammonium ethylene-diaminetetraacetic acid [(NH4)3EDTA] as a sacrificial electron donor and the enzyme ferredoxin NADP+ reductase (FDR) [215, 216]. Oxidative electron-transfer quenching of the excited Ru(bpy)3 + yields the A,A -dimethyl-4,4 -bipyridinium radical cation (reduced methylviologen, MV+), which mediates the reduction of NADP+ in the presence of FDR as a biocatalyst (Figure 32A). The quantum efficiency for NADH production corresponds to = 1.9 x 10 . A related system that includes Zn(II)wc50-(A-tetramethylpyridinium)porphyrin (Zn-TMPyP +) as a photosensitizer, mercaptoethanol as a sacrificial donor and lipoamide dehydrogenase (LipDH) as a biocatalyst has been applied for the photochemical reduction of NAD+ to NADH (Figure 32B). 

In addition, the NMR spectra made it possible to determine the molecular Di symmetry for the [Ru(tabpy)]2 cation in solution [190] and the Cs symmetry for the corresponding semiclathrochelate complex as well as to reveal dynamic effects in macrobicyclic tris-phenanthrolinates and tris-bipyridinates [211]. 

Figure 9. (a) yields as a function of pH in water oxidation with [M(bipy)3] (10 moldm" ) complexes in the presence of RuOi catalyst (10 mol dm ), (b) -pH diagram for water oxidation, RUO4 reduction and redox potentials of tris(bipyridine) complexes (O, [Ru(bipy)3] , [Fefbipy) ] , [Os(bipy)3] ) reproduced from ref. 292)... 

Figure 14. Sonoelectrochemiluminescence of tris-bipyridine ruthenium (II) dichloride ((Ru(bpy)3]Cl2) at platinum in aqueous oxalate solution. Potentiostatic control +1.2 V (SCE). (a) Background zero line, (b) Sonoluminescence from 40-kHz probe, no applied potential, (c) Electrochemiluminescence at +1.2 V (SCE), silent, (d) Sonoelec-trochemiluminescence at 1.2 V (SCE) and ultrasound (40-kHz probe). (Taken from reference 209).

The excellent photophysical properties of Ru(II)-tris(bipyridine) complexes (see Section IV) have been applied to organize D-S-A triads, where a Ru(II)-tris(polypyridine) center acts as photoactive center, lV,lV -trimethy-lene-2,2 -bipyridinium DQ ", or 4,4 -bipyridinium, MV, are the electron acceptor units, and phenothiazine (PTZ), acts as electron donor component [36]. Two different D-S-A triads, formed by direct condensation of the three components (5), or organization of the components on a lysine residue,... 

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