Energy-transfer quenching of excited states of polypyridine complexes of ruthenium(II) by hexaamminecobalt(III) or tris(ethylenediamine)cobalt(III)

Zahir, K. Omar; Boettcher, Wolfhardt; Haim, Albert

doi:10.1021/ic00207a002

Cited by 9 publications

(2 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…30,31 While neither Pt(II) nor Pt(IV) have been reported to induce such fluorescence changes, the results from other d 8 and d 6 ions are encouraging. [32][33][34][35][36] It was hypothesized that changes in fluorescence induced by ligand loss and/or changes in oxidation state could be utilised in microscopy studies to observe the temporal and physical location of these key events.…”

Section: Introductionmentioning

confidence: 99%

Investigations using fluorescent ligands to monitor platinum(iv) reduction and platinum(ii) reactions in cancer cells

et al. 2009

View full text Add to dashboard Cite

Coordination of the aniline containing fluorophores, coumarin 120 (C120) and coumarin 151 (C151) at the non-leaving group positions of cisplatin analogues (giving cis-[PtCl(2)(C120)(NH(3))] and cis-[PtCl(2)(C151)(NH(3))]) resulted in partial and complete quenching of the fluorescence, respectively. Oxidation of the coumarin 120 complex to the Pt(iv) form (cis,trans,cis-[PtCl(2)(OH)(2)(C120)(NH(3))]) resulted in further quenching compared to that seen for the Pt(ii) complex. The fluorescence profiles of these coumarin complexes were collected to evaluate their suitability for studying the metabolism of cisplatin-based anticancer drugs. C151 has the more suitable profile with a lower energy excitation peak and a better separation between the excitation and emission spectra. The complete damping of fluorescence on coordination to Pt(ii) makes it unsuitable for monitoring the reduction process, but does allow it to be used to monitor loss of the aniline type ligand. All of the coumarin complexes revealed moderate cyotoxcities in the range 10-22 microM indicating that they are suitable models of anticancer agents. DNA dampens the fluorescence of both Pt(ii) complexes and that of C120 has a much higher DNA binding affinity (10 000 M(-1)) than does the complex of C151 (300 M(-1)). Treatment of A2780 human ovarian carcinoma cells with the Pt-coumarin complexes resulted in fluorescence visible by confocal microscopy, and co-localisation studies with organelle specific dyes suggest they are concentrated in the late endosomes or lysosomes. Cells treated with the Pt(iv) complex of C120 revealed strong fluorescence and a somewhat different distribution to cells treated with the Pt(ii) complex indicating reduction following uptake.

show abstract

Section: Introductionmentioning

confidence: 99%

Investigations using fluorescent ligands to monitor platinum(iv) reduction and platinum(ii) reactions in cancer cells

et al. 2009

View full text Add to dashboard Cite

show abstract

“…The quantum yield of Co(II) from the quenching of Ru(menbpy) 3 2+ by Co(acac) 3 is less than 1%. The quantum yield for Co(II) products, Φ Co(II) , is given by where the various rate constants are defined in Scheme . As shown by eq 6, the quantum yield is a complex expression that depends on the rate constants for both the electron- and energy-transfer quenching reactions as well as the rate of dissociation of the successor complex and the rate of ligand loss from the Co(II) product.…”

Section: Discussionmentioning

confidence: 99%

Enantioselectivities in Electron-Transfer and Excited State Quenching Reactions of a Chiral Ruthenium Complex Possessing a Helical Structure

et al. 1999

View full text Add to dashboard Cite

The outer-sphere electron-transfer reactions between diastereomers of Ru(menbpy)3 •+ (menbpy = 4,4‘-di{(1R,2S,5R)-(−)-menthoxycarbonyl}-2,2‘-bipyridine) and enantiomers of Co(acac)3 and Co(edta)- have been studied by pulse radiolysis. Δ-Ru(menbpy)3 •+ rapidly reduces Co(acac)3 in 85% EtOH/H2O (1 mM NaH2PO4) with second-order rate constants of (2.1 ± 0.1) × 107 and (7.8 ± 0.2) × 106 M-1 s-1 for the Δ- and Λ-Co(acac)3 enantiomers, respectively, and an enantioselectivity factor (k et Δ/k et Λ) of 2.7. Λ-Ru(menbpy)3 •+ preferentially reduces Λ-Co(acac)3 with an enantioselectivity factor (k et Δ/k et Λ) of 0.8. Activation volume data (ΔV ‡) suggest that the association between the Δ−Δ isomers in the encounter complex allows closer interaction of the metal centers than between the other isomer combinations. The value of k et Δ/k et Λ for the reaction of Δ- and Λ-Co(edta)- with Δ-Ru(menbpy)3 •+ is 1.2. Electron-transfer reactions of seven racemic Ru(L)3 •+ (L = substituted phenanthroline) complexes with Co(acac)3 were also studied and gave rate constants of ≈1.5 × 109 M-1 s-1. The quenching of photoexcited *Ru(menbpy)3 2+ by Co(acac)3 and Co(edta)- exhibits small stereoselectivity: For Co(acac)3 in 95 and 85% EtOH/H2O the enantioselectivity factor is 1.2 and 1.1, respectively, barely outside the experimental error. For all other cases the selectivity was unity within the experimental error of the measurement. The quenching rate constants were ≈1 × 108 and 1.1 × 109 M-1 s-1 for Co(acac)3 and Co(edta)-, respectively. Quenching reactions of seven racemic ruthenium(II) phenanthroline complexes with Co(acac)3 were also studied and found to be faster than those of Ru(menbpy)3 2+ by only a factor of ≈3 despite an increase in the driving force of ≈0.5 eV for electron-transfer quenching. The quenching of *Ru(menbpy)3 2+ by Co(acac)3 is dominated by an energy-transfer mechanism. This conclusion is supported by the magnitude of the quenching rate constants compared with the rate constants for reduction by Ru(menbpy)3 •+, the effect of driving-force changes on the quenching rate constant, the low quantum yield of Co(II) products observed in the CW photolysis, and the lack of long-lived products observed in the flash photolysis experiments. The factors responsible for the selectivity exhibited in the CW photolysis studies of Ru(menbpy)3 2+ with Co(acac)3 are discussed.

show abstract

ChemInform Abstract: ENERGY‐TRANSFER QUENCHING OF EXCITED STATES OF POLYPYRIDINE COMPLEXES OF RUTHENIUM(II) BY HEXAAMMINECOBALT(III) OR TRIS(ETHYLENEDIAMINE)COBALT(III)

Zahir¹,

Boettcher²,

Haim³

1985

Chemischer Informationsdienst

View full text Add to dashboard Cite

Energy-transfer quenching of excited states of polypyridine complexes of ruthenium(II) by hexaamminecobalt(III) or tris(ethylenediamine)cobalt(III)

Cited by 9 publications

References 1 publication

Investigations using fluorescent ligands to monitor platinum(iv) reduction and platinum(ii) reactions in cancer cells

Investigations using fluorescent ligands to monitor platinum(iv) reduction and platinum(ii) reactions in cancer cells

Enantioselectivities in Electron-Transfer and Excited State Quenching Reactions of a Chiral Ruthenium Complex Possessing a Helical Structure

ChemInform Abstract: ENERGY‐TRANSFER QUENCHING OF EXCITED STATES OF POLYPYRIDINE COMPLEXES OF RUTHENIUM(II) BY HEXAAMMINECOBALT(III) OR TRIS(ETHYLENEDIAMINE)COBALT(III)

Contact Info

Product

Resources

About