Kinetics and mechanism of the quenching of the emission of substituted polypyridineruthenium(II) complexes. Reactions of RuL3+, *RuL32+, and RuL33+ with the copper(I)-copper(II) couple

Hoselton, Mitchell A.; Lin, Chin-Tung; Schwarz, Helmut; Sutin, Norman

doi:10.1021/ja00476a021

Cited by 62 publications

(42 citation statements)

References 3 publications

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“…As was observed for copper(II) nitrate and perchlorate, the application of the Debye-Hu¨ckel extended law did not result in a straight line. Our quenching rate constant is lower than any previously published value, [21][22][23] and the applicable kinetic rationale was previously discussed by Hoffman et al 1 Namely, the equation…”

Section: Measurements With Copper(ii) Chloridecontrasting

confidence: 44%

Analysis and improvement of rate constant determination of reactions involving charged reactants

Krise

Hwang

Milosavljevic

2010

Phys. Chem. Chem. Phys.

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Kinetics of tris(2,2'-bipyridine)ruthenium(ii), Ru(bpy)(3)(2+), luminescence quenching by copper(ii) (in the form of chloride, nitrate, sulfate and perchlorate salt) was studied using pulse laser photolysis technique. The pseudo-first order rate constant versus quencher concentration plots obtained were found to be nonlinear, bending upward. The ionic strength effect contribution was evaluated by applying the Debye-Hückel extended law and was found to be as important as other effects such as cation-counter anion complex and ion-pairing complex formation which were all found to be dependent on the counter anion. It is shown that the slope of the tangent line to the pseudo-first order curve at zero quencher concentration is equal to the quenching rate constants at zero ionic strength. Also, this value corresponds to quenching solely by Cu(2+) and is free from contributions from other species that are present at higher concentrations. This method produced a value, (1.6 +/- 0.2) x 10(7) M(-1) s(-1), (lower than previously published ones) which is in agreement with the quenching rate constant measurement analysis presented. Comparison between Stern-Volmer plots obtained using steady-state fluorimetry data and laser photolysis data showed that in 50 mM CuCl(2) and CuSO(4) aqueous solutions about 5% of Ru(bpy)(3)(2+) is in the form of ion-pairing complexes. Our method was also applied to quenching by another divalent cation, methyl viologen, where it was found that charge transfer complexation effect contribution was about 50% of that of ionic strength effect, while ion-pairing complexation was not significant in the concentration range used. The quenching rate constant at zero ionic strength was found to be (2.3 +/- 0.2) x 10(8) M(-1) s(-1). The method proposed is also applicable to pulse radiolysis and stopped flow measurements.

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Section: Measurements With Copper(ii) Chloridecontrasting

confidence: 44%

Analysis and improvement of rate constant determination of reactions involving charged reactants

Krise

Hwang

Milosavljevic

2010

Phys. Chem. Chem. Phys.

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“…The plot of AM vs. ASt has a slope 0) of 256 K. A correlation coefficient of 0.98 is obtained from these data.The magnitude of /3 relative to the experimental temperature determines the extent to which changes in AEF or ASt are communicated to AGt. 6AGt = (1 -;)&AH+(9) …”

mentioning

confidence: 99%

Temperature dependence of excited-state electron-transfer reactions. Quenching of RuL32+ emission by copper(II) and europium(III) in aqueous solution

Baggott¹,

Pilling²

1980

J. Phys. Chem.

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The mechanism of electron-transfer reactions of charge-transfer excited states of ruthenium(I1) complexes containing 2,2'-bipyridine, 1,lO-phenanthroline, and their Substituted derivatives with aquo complexes of copper(I1) and europium(II1) has been investigated by using temperature studies in the range 290-350 K. The europium reactions show the expected increase in rate constant as the overall free-energy change for the reaction (-AGO) increases. The copper sequence shows behavior different from that predicted by Marcus' theory, with rate constants well below the diffusion-controlled limit yet only weakly dependent on AGO. Indeed, increasing (-AGO) is shown to result in increases in the activation energy of the reactions. Several alternative explanations for this behavior are available, many of which can be dismissed in the light of this work. It is suggested that the rate-determining step in the Cu(1I) sequence involves a configuration change in the encounter pair. A similar step may be present in the Eu(II1) series but it must not be rate determining. One model suggests that this step is associated with the necessary distorted-octahedral/tetrahedral geometry change in the reduction of Cu(I1).The temperature dependence of the electron-transfer quenching of *Ru(4,7-Me2phen)t+ by copper(I1) in DzO solvent is also included in the present work in order to test one of the proposed models.

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“…Using the one-electron oxidation potentials for each reducing reagent, 0.36 V for [Ru(hfac) 3 ] − and 0.56 V for [Ni(tacn) 2 ] 2+ , and the self-exchange rate constant for [Ru(hfac) 3 ] 0/− (7.0 × 10 6 M −1 s −1 ) 40 and [Ni(tacn) 2 ] 3+/2+ (1.2 × 10 3 M −1 s −1 ) couples, 41 we estimated the self-exchange rate constant for the Cu(II)/(I) couple as 1.5 × 10 −5 M −1 s −1 and 1.2 × 10 −4 M −1 s −1 (T = 25.0 °C) from these cross reactions, respectively, which may be compared with those estimated for the Cu(II)/(I) couple in water: 10 −7 -10 −3 M −1 s −1 . [43][44][45] These values are given in Table S2. † As these counter reagents, [Ru(hfac) 3 ] − and [Ni(tacn) 2 ] 2+ , are typical outer-sphere reagents, the estimated selfexchange rate constant certainly corresponds to the outer-sphere reaction between solvated Cu 2+ and solvated Cu + .…”

Section: Electron Self-exchange Reactionmentioning

confidence: 99%

Electron transfer reactions between copper(ii) porphyrin complexes and various oxidizing reagents in acetonitrileElectronic supplementary information (ESI) available: Figures reporting the UV-visible absorption spectra of [Cu(OEP)] and the product of the reaction of [Cu(OEP)] with Cu(ii) triflate in acetonitrile, the dependence of the absorbance on the ratio of the total concentrations of Cu(ii) ion and [Cu(OEP)] for the reaction of [Cu(OEP)] and Cu(ii) triflate, and the dependence of the pseudo-first-orde

et al. 2004

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Homogeneous electron transfer reactions of the Cu(II) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) with various oxidizing reagents were spectrophotometrically investigated in acetonitrile. The reaction products were confirmed to be the pi-cation radicals of the corresponding Cu(II)-porphyrin complexes on the basis of the electronic spectra and the redox potentials of the complexes. The rate of the electron transfer reaction between the Cu(II)-porphyrin complex and solvated Cu(2+) was determined as a function of the water concentration under the pseudo first-order conditions where Cu(2+) is in large excess over the Cu(II)-porphyrin complex. The decrease in the pseudo first-order rate constant with increasing the water concentration was attributed to the stepwise displacement of acetonitrile in [Cu(AN)(6)](2+)(AN = acetonitrile) by water, and it was concluded that only the Cu(2+) species fully solvated by acetonitrile, [Cu(AN)(6)](2+), possesses sufficiently high redox potential for the oxidation of Cu(ii)-OEP and Cu(ii)-TPP. The reactions of the Cu(II)-porphyrin complexes with other oxidizing reagents such as [Ni(tacn)(2)](3+)(tacn = 1,4,7-triazacyclononane) and [Ru(bpy)(3)](3+)(bpy = 2,2'-bipyridine) were too fast to be followed by a conventional stopped-flow technique. Marcus cross relation for the outer-sphere electron transfer reaction was used to estimate the rate constants of the electron self-exchange reaction between Cu(II)-porphyrin and its pi-cation radical: log(k/M(-1) s(-1))= 9.5 +/- 0.5 for TPP and log(k/M(-1) s(-1))= 11.1 +/- 0.5 for OEP at 25.0 degrees C. Such large electron self-exchange rate constants are typical for the porphyrin-centered redox reactions for which very small inner- and outer-sphere reorganization energies are required.

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Kinetics and mechanism of the quenching of the emission of substituted polypyridineruthenium(II) complexes. Reactions of RuL3+, *RuL32+, and RuL33+ with the copper(I)-copper(II) couple

Cited by 62 publications

References 3 publications

Analysis and improvement of rate constant determination of reactions involving charged reactants

Analysis and improvement of rate constant determination of reactions involving charged reactants

Temperature dependence of excited-state electron-transfer reactions. Quenching of RuL32+ emission by copper(II) and europium(III) in aqueous solution

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