Mechanisms of Photoreactions in Solution. XX.<sup>1</sup> Quenching of Excited States of Benzophenone by Metal Chelates

Hammond, George S.; Foss, Robert P.

doi:10.1021/j100794a034

Cited by 42 publications

(11 citation statements)

References 2 publications

(2 reference statements)

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“…Also, the differences in the quenching efficiency of the cis and trans isomers of Cr-(en)2X2+ and Cr(en)2XY+ led to the suggestion that geometric factors play some role in determining quenching efficiency.23 Although this suggested structural dependence is somewhat clouded due to the differences in the electronic structure of the isomers, the importance of steric hinderence is indicated in the quenching of organic triplets by the higher efficiency of acetylacetonate complexes as compared to dipivaloylmethanate complexes. , 22 The difference in the quenching efficiency found with the latter complexes is substantially larger than that found in these experiments. With these geometric isomers, however, the molecular size is essentially the same and the structural difference arises from the complex as a whole.…”

Section: Resultscontrasting

confidence: 56%

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

Huang¹,

Gafney²

1977

J. Phys. Chem.

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The effect of molecular structure on the quenching of the luminescent charge-transfer state of Ru(bpy)32+ and Ru(bpic)32+ has been studied with eight geometric ß-diketonate isomers of Co(III) and Cr(III). The isomers have identical electronic spectra, but differ in their molecular structure. The Co(III) isomers quench at essentially a diffusion-controlled limit, whereas the Cr(III) isomers quench at an order of magnitude less than the theoretical limit. The cis and trans isomers of the Co(III) complexes yield identical Stern-Volmer constants suggesting little or no discrimination during the quenching encounter. A similar lack of discrimination is found with the phenyl substituted Cr(III) complex, Cr(bzac)3. With the trifluoro-substituted analogue, however, cis-Cr(tfac)3 is ca. 40% more efficient in quenching than trans-Cr(tfac)3.

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Section: Resultscontrasting

confidence: 56%

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

Huang¹,

Gafney²

1977

J. Phys. Chem.

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“…65 It is also known from literature that, as a result of electron transfer processes from the imidazolium cation to the trivalent lanthanide, Eu(II) is present in C 4 mimTf 2 N. 66 Moreover, spin-forbidden transitions of atomic molecules in their excited triplet atomic states can be enhanced by their interaction with paramagnetic molecules 67 or ions. 68 Hill and Lin describe the quenching of naphthalene fluorescence by Cu(II) besides Cr(III), Co(II) and Ni(II) 69 while Steiner and Kirby postulate the quenching of excited indole by abstraction of an electron by scavengers such as Cu(II), Mn(II), Cd(II) or Pb(II). 70 Because of the aromatic character of the imidazolium cation of C 4 mimTf 2 N an electron transfer between the IL and Eu(III) as well as the scavenger Cu(II) seems to be plausible.…”

Section: Quenching Reaction In C 4 Mimtf 2 N Compared To H 2 Omentioning

confidence: 99%

Differences of Eu(iii) and Cm(iii) chemistry in ionic liquids: investigations by TRLFS

et al. 2007

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In this study the coordination structure and chemistry of Eu(III) and Cm(III) in the ionic liquid C(4)mimTf(2)N (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) was investigated by time-resolved laser fluorescence spectroscopy (TRLFS). The dissolution of 1 x 10(-2) M Eu(CF(3)SO(3))(3) and 1 x 10(-7) M Cm(ClO(4))(3) in C(4)mimTf(2)N leads to the formation of two species for each cation with fluorescence emission lifetimes of 2.5 +/- 0.2 ms and 1.0 +/- 0.3 ms for the Eu-species and 1.0 +/- 0.3 ms and 300.0 +/- 50 micros for the Cm-species. The interpretation of the TRLFS data indicates a comparable coordination for both the lanthanide and actinide cation in this ionic liquid. The quenching influence of Cu(II) on the fluorescence emission of Eu(III) and Cm(III) was also measured by TRLFS. While Cu(ii) does not quench the Cm(III) fluorescence emission in C(4)mimTf(2)N the Eu(III) fluorescence emission lifetime for both Eu-species in C(4)mimTf(2)N decreases with increasing Cu(II) concentration. Stern-Volmer constants were calculated (k(SV) = 1.54 x 10(6) M(-1) s(-1) and k(SV) = 2.70 x 10(6) M(-1)). By contrast, the interaction of Cu(II) with Eu(III) and Cm(III) in water leads to a quenching of both the lanthanide and actinide fluorescence. The calculated Stern-Volmer constants are 1.20 x 10(4) M(-1) s(-1) for Eu(III) and 1.27 x 10(4) M(-1) s(-1) for Cm(III). The investigations show, while the chemistry of trivalent lanthanides and actinides is similar in an aqueous system it is dramatically different in ionic liquids. This difference in chemical behavior may provide the opportunity for a separation of lanthanides and actinides with regard to the reprocessing of nuclear fuel.

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“…The concentration of all metal ions is 2.5 X lo-4M . The fact that their results are not entirely consistent with ours is perhaps not surprising since their measure- 10 15…”

Section: Resultsmentioning

confidence: 52%

Quenching of Phosphorescence by Paramagnetic Molecules in Rigid Media. II. Quenching of Perdeuderated Naphthalene by Co++, Cr3+, Cu++, and Ni++

Hill

Lin

1970

The Journal of Chemical Physics

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Experimental observation of the steady-state phosphorescence emission intensity of perdeuterated naphthalene as a function of paramagnetic quencher concentrations has been carried out in solid matrices of ethyl alcohol at liquid-nitrogen temperature. The paramagnetic quenchers chosen for study are the transition-metal ions, Co+ +, Cr3+, Cu+ +, and Ni+ +. The decay curves of 'phosphorescence are nonexponential, and the deviation from the exponentiality depends on the concentrations of quenchers. The experimental results are correlated and interpreted by using theoretical expressions derived from the Hoijtink's exchange interaction mechanism.

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Mechanisms of Photoreactions in Solution. XX.¹ Quenching of Excited States of Benzophenone by Metal Chelates

Cited by 42 publications

References 2 publications

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

Differences of Eu(iii) and Cm(iii) chemistry in ionic liquids: investigations by TRLFS

Quenching of Phosphorescence by Paramagnetic Molecules in Rigid Media. II. Quenching of Perdeuderated Naphthalene by Co++, Cr3+, Cu++, and Ni++

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Mechanisms of Photoreactions in Solution. XX.1 Quenching of Excited States of Benzophenone by Metal Chelates

Cited by 42 publications

References 2 publications

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

The effect of molecular structure on the quenching of the charge-transfer luminescence of ruthenium(II) complexes

Differences of Eu(iii) and Cm(iii) chemistry in ionic liquids: investigations by TRLFS

Quenching of Phosphorescence by Paramagnetic Molecules in Rigid Media. II. Quenching of Perdeuderated Naphthalene by Co++, Cr3+, Cu++, and Ni++

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Mechanisms of Photoreactions in Solution. XX.¹ Quenching of Excited States of Benzophenone by Metal Chelates