Ru polypyridyl complex

Reactions of of high oxidation state osmium and Ru polypyridyl complexes have been reviewed [43]. 

The lowest energy MLCT transition of Ru polypyridyl complexes of the type tris-[Ru(4,4/-dicarboxy-2,2/-bipyridine)3] (1), can be lowered so that it absorbs more in the red region of the visible spectrum by replacing one 4,4/-dicarboxy-2,2/-bipyridine (dcbpy) with two thiocyanate donor ligands [Ru(dcbpy)2(NCS)2] (2). In complex 2, the two 4,4/-dicarboxylic acid 2,2 -bipyridine ligands pull while the two thiocyanate donor ligands push electrons. The oxidation potential of the complex 2 is 0.85 V vs. SCE, which is cathodically shifted significantly (0.65 V vs. SCE) compared to the homoleptic type of complex 1, which shows Ru(III/II) couple at 1.5 V vs. SCE. Thus, the... 

In the light of the rapid excited-state relaxation dynamics and the observed <100 fs electron injection component, the fast injection component must occur from non-equilibrated excited states. Distinct singlet and triplet electron-injection pathways have been observed for Ru polypyridyl complexes on SnOa (Iwai et al, 2000) and TiOi (Benko et al, 2002 Kalloinen et al, 2002). In a detailed study of electron injection dynamics in N3/TiOi (Benko et al, 2002 Kalloinen et al, 2002), 55% of electron injection was shown to occur with 50 fs injection time from singlet MLCT... 

Ai X., Anderson N. A., Guo J. and Lian T. (2005), Electron injection dynamics of Ru polypyridyl complexes on SnOi nanocrystalline thin films , J. Phys. Chem. B 109, 7088-7094. 

Run(Hedta)(NO+)]° and [Fen(Hedta)(NO )] have been shown to be effective electrocatalysts for the reduction of N02 in acidic aqueous media, to yield N20, N2, NH3OH+, or NH4 339,340 An element of selectivity is available by control of pH and applied potential. Steps involved in the typical six-electron reduction of nitrite to ammonia catalyzed by [Run(Hedta)(NO+)]° are summarized in Equations (67)-(69). The mechanisms by which nitrite is reduced appeared to be similar to those identified for Fe-porphyrin331 and Ru or Os-polypyridyl complexes.337... 

The Langmuir-Blodgett method has been used to prepare hybrid films of an anionic Ru(ll) cyanide polypyridyl complex with LDHs [170]. An LDH film was formed on mica owing to the interaction between LDHs particles and the Ru(ll) cyanide polypyridyl complex that was pre-dispersed on the surface of mica. Water-in-oU emulsions composed of octane, water and sodium dodecyl sulfate (SDS) have been used to synthesize Mg/Al LDHs with carbonate as the interlayer anion [171] by constant pH or variable pH methods. A floccule or fiber-like LDH material that possesses similar chemical composition and properties to that synthesized using a conventional variable pH method was obtained. The resulting LDH shows high surface area and a narrow distribution of mesopores. 

Fig. 1. Schematic diagram of molecular orbitals and electronic transitions in the case of most polypyridyl Ru(II) complexes...

Table 2. List of polypyridyl Ru(II) complexes studied in the presence of DNA...

The photophysics and photochemistry of Ru(II) complexes have been extensively studied and good reviews are av able on this subject [1,86,87]. The type of reactivity associated with Ru(II) polypyridyl complexes in the excited state depends on the nature of this excited state and consequently on the different possible photophysical pathways controlling the luminescence lifetimes. For most polypyridyl Ru(II) complexes (for example Ru(bpy), Rufphenls", Ru(bpz)3. .. Fig. 2) [1, 86, 87], population of the excited singlet MLCT state is followed by crossing to the triplet MLCT state ( MLCT) with a quantum yield... 

On the basis of the reduction potential of Rh(phen) (Eo = — 0.75 V/SCE) and of its nn energy (2.75 eV), Rh(phen)3 in the nn state is expected to be a very powerful oxidising agent (with a reduction potential of 2.0 V/SCE [133]), making it a stronger oxidant than the MLCT states of the Ru(II) complexes discussed above. Electron transfer from aromatic amines [134] or di-and tri-methoxybenzenes [135] to excited Rh(III) polypyridyl complexes have indeed been observed. 

It has been shown that polypyridyl Rh(III) complexes induce photo-cleavages of the sugar phosphate backbone of double-stranded DNA with a higher relative quantum yield than Ru(II) complexes of phen or DIP. Thus replacement of Ru(II) ions by Rh(III) in Tris(phen) complexes, increases the efficiency of DNA photo-cleavages. However, in contrast to the Ru(II) complexes, Rh(III) samples have to be illuminated in the UV because of the absence of absorption bands in the visible region. 

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