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A series of hetero- and homoleptic tridentate ruthenium(II) and osmium(II) complexes of compositions [(tpy-PhCH3)Ru(tpy-HImzphen)](ClO4)2 (1), [(H2pbbzim)Ru(tpy-HImzphen)](ClO4)2 (2), and [M(tpy-HImzphen)2](ClO4)2 [M = RuII (3) and OsII (4)], where tpy-PhCH3 = 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine, H2pbbzim = 2,6-bis(benzimidazole-2-yl)pyridine and tpy-HImzphen = 2-(4-[2,2′:6′,2″]terpyridine-4′-yl-phenyl)-1H-phenanthro[9,10-d]imidazole, have been synthesized and characterized by using standard analytical and spectroscopic techniques. X-ray crystal structures of three complexes 2, 3, and 4 have been determined. The absorption spectra, redox behavior, and luminescence properties of the complexes have been thoroughly investigated. All of the complexes display moderately strong luminescence at room temperature with lifetimes in the range of 10-55 ns. The effect of solvents on the absorption and emission spectral behavior of the complexes has also been studied in detail. The anion sensing properties of all the complexes have been studied in solution using absorption, emission, and 1H NMR spectral studies and by cyclic voltammetric (CV) measurements. It has been observed that the complexes 1, 3, and 4 act as sensors for F-only, whereas 2 acts as sensor for F-, AcO-, and to some extent for H2PO4-. It is evident that in the presence of excess of anions deprotonation of the imidazole N-H fragment(s) occurs in all cases, an event which is signaled by the development of vivid colors visible with the naked eye. The receptor-anion binding/equilibrium constants have been evaluated. [ABSTRACT FROM AUTHOR]

We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H2ase) by CO. We present a model study, using a NiRu H2ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the RuII center rather than taking an axial position on the NiII center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H2ase by complexing to the FeII center. [ABSTRACT FROM AUTHOR]

Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, RuIII and PtIV metal ions share basically the same principle. Both RuIII- and PtIV-bound G have highly positively polarized C8--H's that are susceptible to deprotonation by OH-, and both undergo two-electron redox reactions. The main difference is that, unlike PtIV, RuIII is thought to require O2 to undergo such a reaction. In this study, however, we report that [RuIII(NH3)5(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5'-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O2. In the presence of O2, 8-oxo-dGuo and cyclic-dGuo were observed. Both [RuII(NH3)5(dGuo)] and cyclic-dGuo were produced from [RuIII(NH3)5(dGuo)] accelerated by [OH-]. We propose that [RuIII(NH3)5(dGuo)] disproportionates to [RuII(NH3)5(dGuo)] and [RuIV(NH3)4(NH2-)(dGuo)], followed by a 5'-OH attack on C8 in [RuIV(NH3)4(NH2-)(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to RuIV, generating cyclic-dGuo and RuII without involving O2. [ABSTRACT FROM AUTHOR]

Compares the hole-transfer superexchange in dinuclear mixed-valence ruthenium complexes. Mechanism of hole-transfer; Reagents and methodology used in the study; Isolation of triammine complexes.

The treatment of [Ru(LOEt)(N)Cl2] (1; LOEt- = [Co(η5-C5H5){P(O)(OEt)2}3]-) with Et3SiH affords [Ru(LOEt)Cl2(NH3)] (2), whereas that with [Ru(LOEt)(H)(CO)(PPh3)] (3) gives the dinuclear imido complex [(LOEt)Cl2Ru(μ-NH)Ru(CO)(PPh3)(LOEt)] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) Å. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10-5 M-1 s-1. [ABSTRACT FROM AUTHOR]