Excited state acid-base reactions of transition metal complexes: dicyanobis(2,2'-bipyridine) ruthenium(III) in aqueous acid

Peterson, Steven H.; Demas, J. N.

doi:10.1021/ja00440a100

Cited by 51 publications

(35 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…5 orders of magnitude. 5 The [H + ] dependence of the quantum yield of dissociation of the bimetallic [bpy) 2 Ru(CN)(µ-CN)Rh(NH 3 ) 4 Br] 2+ and the appearance of a (bpy) 2 Ru(CN) 2 emission from a bimetallic composed of two components that, as individual molecules quench at a diffusion controlled rate, led to the suggestion that optical excitation of the (bpy) 2 Ru(CN) 2 ligand in [bpy) 2 Ru(CN)(µ-CN)Rh(NH 3 ) 4 Br] 2+ leads to a dissociative excited state. 6 Dissociation is attributed to the reduction in electron density at the cyano groups as evidenced by the decrease in their basicity on the population of the (bpy) 2 Ru(CN) 2 ligand's MLCT state.…”

Section: Introductionmentioning

confidence: 99%

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

2009

View full text Add to dashboard Cite

The proton dependencies of the absorption and emission spectra of bis(2,2′-bipyridyl)(2,3-bis(2-pyridyl)pyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ indicate that population of the dpp-localized MLCT state increases the basicity of dpp peripheral nitrogens. NMR spectra reveal the protonation of the peripheral dpp pyridine in the ground state, pK a of 1.12 ( 0.03, occurs intermediate between the changes evident in the absorption and emission spectra. As a result, the emissivity of aqueous solutions of (bpy) 2 Ru(dpp) 2+ as a function of [H + ] derives from two emissive species: the unprotonated complex and the monoprotonated complex [(bpy) 2 Ru(dppH py )] 3+ with the proton attached to the peripheral dpp pyridine. Although protonation in the MLCT state generally quenches the emission, the emissivity of the monoprotonated complex, albeit weak, is attributed to the asymmetric distribution of the charge in the MLCT state. The majority of the transferred charge resides at the peripheral pyrazinyl nitrogen, and excited-state acid-base chemistry occurs predominantly at this site. Nonetheless, ground-state protonation of the peripheral dpp pyridine dramatically increases the nonradiative decay rate and significantly influences subsequent excited-state protonation processes. Protonation of the excited state changes from a bimolecular process to a combination of inter-and intramolecular processes where the proton transfers from the dpp pyridyl nitrogen to the dpp pyrazinyl nitrogen and from the surrounding aqueous solvent shell. Energetically, changes in the absorption spectra originally attributed to the first protonation of the complex and from which the ∆pK a of the excited state have been estimated, in fact, correspond to the second protonation of the complex. IntroductionThe hydrogen ion dependencies of the absorption and emission spectra of Ru(II) diimines reveal substantial differences in the acid-base properties of the ground and emissive MLCT states of the complexes. 1 Depending on the direction of the charge transfer relative to the acid-base site, and the location of the acceptor orbital in the MLCT state, excitation changes electron distribution, which in turn increases or decreases acid-base properties by as much as 5 to 6 orders of magnitude. 2 Brønsted basicity usually does not correlate with the coordinating ability of a ligand, but, with diimine ligands, the equilibrium constant for coordination increases linearly with the Brønsted basicity of the ligand's coordinating nitrogens. 3 Work in this laboratory focuses on whether these photoinduced changes in acid-base properties translate into an excited-state coordination chemistry where a Ru(II) diimine possessing one or more acid-base sites on the ligand periphery functions as a ligand and whether excitation enhances or reduces its ability to coordinate to another metal.Excited-state coordination chemistry arises from the observation that excitation of bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II), (bpy) 2 Ru(dpp) 2+ , in the presence of PtCl 6

show abstract

Section: Introductionmentioning

confidence: 99%

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

2009

View full text Add to dashboard Cite

show abstract

“…7 The ground-17 and excited-state protonations of cyanide ligands of this complex have been observed in acidic aqueous solution. 3 Moreover, the cyanide ligands behaved as electron donors when interacting with acceptor solvents and the protonation caused by this interaction has been measured. 1 Cyclic voltammetry indicated a stable form of doublyreduced complex derived from [Ru(CN) 2 (bpy) 2 ], and the doubly-reduced complex contained two one-electron reduced bipyridine ligands.…”

Section: Discussionmentioning

confidence: 99%

“…The most evident feature of this complex is the solvent-dependence of the absorption spectra, emission spectra and redox potential, when contrasted with the essentially solventindependent behavior of [Ru(bpy) 3 ] 2+ . 1 The cyanide ligands in [Ru(CN) 2 (bpy) 2 ] act as an electron donor in second-sphere donor-acceptor (SSDA) interactions with acceptor solvents.…”

Section: Introductionmentioning

confidence: 97%

“…1 [Ru(CN) 2 (bpy) 2 ] is a good luminescence donor and shows long-lived charge transfer emission in solution. 3 This complex undergoes a variety of photoredox reactions. 4 The energies of metal-to-ligand charge transfer (MLCT) absorption and emission indicate good correlations with the Gutmann acceptor number of the solvents, and these correlations are observed over an extended series of solvents.…”

Section: Introductionmentioning

confidence: 99%

“…7 One-electron reduction from the matrix 8 and the intercomponent transfer process of ruthenium bipyridine complexes in the excited state during the ioni-zation process were observed in FAB mass spectra. 9 The formation process of a doubly-charged ion of [Ru(bpy) 3 ] 2+ observed in FAB mass spectra with 3-nitrobenzylalcohol, was related to an oxidative quenching of the excited state of the complex. 10 From the viewpoint of the correlation of LSIMS mass spectra with solution chemistry and photochemistry, we have examined how chemical species were formed during the ionization process by analyzing LSIMS mass spectra of [Ru(CN) 2 (bpy) 2 ] with 3-mercapto-1,2-propanediol (thioglycerol) containing a glycerol matrix, by the leastsquares method.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The reduction and oxidation reactions of [Ru(CN)2(bpy)2] observed in liquid secondary ion mass spectra with a thioglycerol matrix

Tanaka

Nagai

Miki

et al. 1997

Eur. J. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

ChemInform Abstract: EXCITED STATE ACID‐BASE REACTIONS OF TRANSITION METAL COMPLEXES‐ DICYANOBIS(2,2′‐BIPYRIDINE) RUTHENIUM(III) IN AQUEOUS ACID

Peterson¹,

Demas²

1977

Chemischer Informationsdienst

View full text Add to dashboard Cite

Excited state acid-base reactions of transition metal complexes: dicyanobis(2,2'-bipyridine) ruthenium(III) in aqueous acid

Cited by 51 publications

References 0 publications

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

Excited-State Coordination Chemistry: Excited-State Basicity of Bis(2,2′-bipyridyl)(2,3-dipyridylpyrazine)ruthenium(II)

The reduction and oxidation reactions of [Ru(CN)2(bpy)2] observed in liquid secondary ion mass spectra with a thioglycerol matrix

ChemInform Abstract: EXCITED STATE ACID‐BASE REACTIONS OF TRANSITION METAL COMPLEXES‐ DICYANOBIS(2,2′‐BIPYRIDINE) RUTHENIUM(III) IN AQUEOUS ACID

Contact Info

Product

Resources

About