Ru Bipy Research Articles

Light-induced electron-transfer reactions. Part 1. Kinetics of formation of hydrogen peroxide by irradiation with visible light of aqueous solutions containing tris(2,2′-bipyridine)ruthenium(II), oxalic acid, manganese(II), and oxygen

Hydrogen peroxide is formed by the light-catalyzed reaction of [Ru(bipy)3]2+(bipy = 2,2′-bipyridine) in an aqueous dilute sulphuric acid solution containing oxalic acid, manganese(II) sulphate, and oxygen. The amount of H2O2 formed increases greatly with increasing intensity of visible light, with increasing concentration of [Ru(bipy)3]2+ or oxygen, and with increasing concentration of manganese(II), and increases linearly with increasing hydrogen-ion concentration up to about 0.3 mol dm–3 but then decreases with further increase. On the other hand, the rate of formation of H2O2 is almost independent of the concentration of oxalic acid when [H2C2O4] < [MnII] and slightly decreases when [H2C2O4][MnII]. No formation of H2O2 is found in the dark or in the absence of any one of [Ru(bipy)3]2+, manganese(II), and oxalic acid. The formation of H2O2 is greatly retarded by the presence of copper(II) sulphate or methylviologen. A chain mechanism of reaction is proposed to account for these facts.

Light-induced Electron Transfer from Tris(2,2′-bipyridine)ruthenium(II)2+ to a Nickeldithiolene in Homogeneous and Heterogeneous Systems

We have investigated the reduction of Nickel-tetraphenyldithiolene by 2-aminonaphthalene with Ru(bipy)3 2+ as a photocatalyst and found a quantum yield of approximately 1 % for the conditions of our homogeneous system. The lifetime of Ru(bipy)3 2+ is increased from 600 to 800 ns when micelle formation in aqueous solutions of anionic surfactants takes place. No such change.in lifetime is found in nonionic micelles. In a three compartment system the light driven electron transport from one aqueous compartment containing the Ru(bipy)3 2+/EDTA system through a membrane containing Ni-dithiolene in an organic solvent to tbe second aqueous compartment containing Na3[Fe(CN)6] is investigated. It is shown that direct electron transfer from the excited ruthenium complex to Ni-dithiolene across the phase boundary can be effected by the action of an anionic surfactant.

Ruthenium complexes with diazadienes. Part II Syntheses and N.m.r. spectroscopic characterization of [Ru(bipy)2(diazadiene)]2+ complexes

Thermal substitution of chloride in Ru(bipy)2Cl2 · 2H2O with diazadienes (dad) R′N=CR-CR=NR′ yields the mixed [(bipy)2Ru(dad)]2+ complexes, which are analogous to the [Ru(bipy)3]22+ cation. Full n.m.r. assignments are given for several complexes; conformational rigidity is displayed by dad-attached phenyl groups in one of them. The u.v. spectra, which show dad-dependent first c.t.-absorption bands, are compared to that of [Ru(bipy)3]2+.

Flash-photolysis studies of the electron-transfer reactions of dioxygen complexes of cobalt(III) with tris(2,2′-bipyridyl)ruthenium(III)

Electron-transfer reactions between the µ-peroxo-cobalt(III) complexes [(H3N)5Co(µ-O2)Co(NH3)5]4+(1), [(H3N)4Co(µ-O2)(µ-NH2)Co(NH3)4]3+(2), and [(L–L)2Co(µ-O2)(µ-NH2)Co(L–L)2]3+[L–L = ethylenediamine (3), 2,2′-bipyridyl (4), or 1,10-phenanthroline (5)] and [Ru(bipy)3]3+(bipy = 2,2′-bipyridyl) have been investigated. The reactants have been generated by the electron-transfer quenching of the excited state of [Ru(bipy)3]2+ by the corresponding µ-superoxo-complexes using flash photolysis. The half-wave potentials measured by polarography for complexes (3), (4), and (5) are 1.00 ± 0.05, 1.04 ± 0.05, and 1.04 ± 0.05 V respectively. The observed rate constants are used to calculate the self-exchange electron-transfer rate constants for the bridged cobalt(III) complexes. The Marcus cross relationship has been used to predict the rate constants determined earlier for the electron-transfer reaction between (3) and the superoxo-forms of complexes (1), (4), and (5).

Chemiluminescence from electron transfer reactions of transition metal complexes

Abstract Chemiluminescence experiments were carried out with several transition metal complexes in fluid solution, using continuous and/or stop—flow techniques. The oxidation of Cr(II) polypyridine complexes by S2O82- led to luminescence emission from the 2Eg metal-centred excited state (2MC) of the corresponding Cr(III) complexes. The reduction of Ru(III) polypyridine complexes (including the mixed ligand Ru(bipy)2(DMCH)3+ complex) by OH− or C2O42- led to luminescence emission from the triplet charge transfer excited state of the corresponding Ru(II) complexes. The mixing of Cr(II) and Ru(III) polypyridine complexes led to luminescence emission from the 2MC of the corresponding Cr(III) complexes. The mechanistic and energetic aspects of these chemiluminescence processes are discussed.

Bis(2,2′bipyridine) ruthenium(II) complexes

Abstract A reinvestigation of the photolysis of [Ru(bipy)3](NCSe)2 in ethanol under dinitrogen has failed to give the previously reported [Ru(N3)2bipy2] but, under appropriate conditions, may yield the complex [Ru(NCO)2bipy2].

Reduction chemistry of hydrido(triethylphosphine) complexes of platinum(II) or palladium(II) and aqueous chemistry of tris(triethylphosphine)palladium(0)

Sodium or magnesium amalgam reductions of tetrahydrofuran solutions of [MH(PEt3)3][BPh4](M = Pt or Pd), or of toluene solutions of [PtH(Cl)(PEt3)2] in the presence of an excess of PEt3, produce hydrogen and [Pt(PEt3)3] or Pd metal. The mechanism of the reaction is discussed and [Ru(bipy)3]2+*(bipy = 2,2′-bipyridyl) is shown not to reduce [PdH(PEt3)3]+ in aqueous solution. The compound [Pd(PEt3)3] dissolves in buffered or acidic water to produce [PdH(PEt3)3]+ although it is less nucleophilic than [Pt(PEt3)3]. In the presence of chloride ion at low pH, [PdH(Cl)(PEt3)2] is formed in high yield.

Kinetics of the catalysed oxidation of H 2O by Ru(bipy) 32+

Kinetics of the catalysed oxidation of H 2O by Ru(bipy) 32+

Ru(bipy) 32+-sensitized photooxidation of cis-stilbenes

Ru(bipy) 32+-sensitized photooxidation of cis-stilbenes

Luminescence from [Ru(bipy)3]2+ ions adsorbed on ion exchange surfaces. Dynamic quenching reactions between adsorbed cations

Luminescence lifetime measurements show that when both luminescent and quencher ions are adsorbed on cation exchange resin luminescence quenching takes place by dynamic bimolecular processes involving energy transfer or electron transfer at rates which are of the same order as those in homogeneous solution.

Equilibria in complexes ofN-heterocyclic molecules, Part XV+. Intermediates in the reaction of cyanide with transition metal tris complexes of 1,10-phenanthroline, 5-nitro-1,10-phenanthroline and 2,2'-bipyridyl

The Ru(phen)3(CN)2 · 6 H2O, Ru(bipy)3(CN)2 · 6H2O, Fe(phen)3(CN)2 · H2O and Ru(5-NO2P)3(CN)2 · 2 H2O compounds have been isolated during the reaction of the parent cations with aqueous cyanide solutions. It is evident, that in each case, attack at the ligand has taken placevia the cyanide nucleophile, though the equilibrium constant for the formation of the Reissert-type species are widely different. The implications of the findings with respect to the known reaction kinetics of the parent ions in aqueous cyanide solution are discussed.

Laser photoelectrochemistry as a tool for studies of metal complex excited states

Photocurrents from argon ion laser irradiation of [Ru(bipy)3]2+ at an SnO2 electrode in the presence of Fe3+ as a scavenger may be analysed to yield the excited state lifetime in a manner which can be extended to nonluminescent excited states.