Ruthenium complexes spectra

However upon standing at ambient conditions the solutions precipitate Ru3(CO)i2 in nearly quantitative yields. Infrared spectra under reaction conditions (400 atm of 1 1 H2/CO, 200°C) also correspond to the spectrum of Ru(CO)5 no acetate or cluster complexes are observed. However, there is evidence for the presence of small amounts of Ru3(CO) 2 under somewhat lower pressures (ca. 200 atm) Many other ruthenium complexes were used as catalyst precursors, and were found to be converted to the same ruthenium products under reaction conditions. For example, H4Ru4(CO)12 (13), [Ru(CO)2(CH3C02)2ln (14) ... 

In the example discussed above, the heterotriad consists of a photosensitizer and an electron donor. In the following example, a ruthenium polypyridyl sensitizer is combined with an electron acceptor, in this case a rhodium(lll) polypyridyl center [15]. The structure of this dyad is shown in Figure 6.21 above. The absorption characteristics of the dyad are such that only the ruthenium moiety absorbs in the visible part of the spectrum. Irradiation of a solution containing this ruthenium complex with visible light results in selective excitation of the Ru(ll) center and in an emission with a A.max of 620 nm. This emission occurs from the ruthenium-polypyridyl-based triplet MLCT level, the lifetime of which is about 30 ns. This lifetime is very short when compared with the value of 700 ns obtained for the model compound [Ru(dcbpy)2dmbpy)], which does not contain a rhodium center. Detailed solution studies have shown that this rather short lifetime can be explained by fast oxidative quenching by the Rh center as shown in the following equation ... 

Analogous to the supramolecular TRPyP systems, the tetramthenated porphyr-azine species also form homogeneous molecular films on solid substrates, by the slow evaporation of the solvent. Such films are suitable for the preparation of modified electrodes displaying versatile electrochemical and photoelectrochem-ical properties. The spectrum of a TRPyPz film on ITO is analogous to the solution spectrum exhibiting the Soret band at 390 and a broad Q band at 705 nm, respectively and the peripheral ruthenium complexes n-n and CT bands at 300 and 500 nm (125, 126). 

The photocatalytic oxidation of N2 by a suspension of Pt/Ti02/Ru02 in an aqueous solution of the ruthenium complex [Ru(HEDTA)N2] was reported by Taqui Khan et al. in a 1989 communication [112]. The complex that was actually used as a starting material was K[Ru(HEDTA)C1]-2H20. Taqui Khan stated that [Ru(HEDTA)Cl] was converted to [Ru(HEDTA)N2] and [(Ru(HEDTA))2N2]2 in situ by photochemical interaction with the irradiated Pt/Ti02/Ru02 in the presence of N2 gas. The dinitrogen complexes were identified by bands in the UV spectrum at 225 and 278 nm, respectively. 

K2[Ru(CN)5 NO)], the only fully estabhshed nitrosyl cyanide ruthenium complex, is prepared by reaction of K4[Ru(CN)j] with HN03. Its Mossbauer spectrum, which shows a more positive isomer shift than K4[Ru(CN)g], is ascribed to the greater n acceptor ability of NO" compared to CN . For K4[Ru(CN)5(N02)], prepared by reaction of K2[Ru(CN)5NO] with a decrease... 

The photoreduction of 1 by triethylamine occurs in a variety of solvents including isobutyronitrile, THF, acetonitrile-isopropyl alcohol, methylene chloride, and chloroform although the reaction does not appear to be clean or to go to completion in the latter two solvents. Quantum yields measured thus far are 0.35, 0.2, and 0.05 in dry acetonitrile, isobutyronitrile, and THF, respectively. Although the reduced ruthenium complex, RuLs, is stable on a time scale of minutes to hours, we find that the pre-irradiation spectrum of RuLs is slowly regenerated on a time scale of hours to days in degassed solutions allowed to stand in the dark at 20°-25°C. Admission of air to the samples results in instantaneous regeneration of the spectrum of RuLs. As mentioned above, the overall reaction sequence appears best described by Reactions 9, 14, and 16 as outlined below. This predicts a limiting quantum yield of two for... 

---