Electron donor-acceptor quenching and photoinduced electron transfer for coumarin dyes

Jones, Guilford; Griffin, Susan F.; Choi, Chol Yoo; Bergmark, William R.

doi:10.1021/jo00189a010

Cited by 88 publications

(60 citation statements)

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“…The free energies of photo-electron transfer process (DG ET ) between the azo dyes and the quenchers are found to be about À19 kcal/mol. All of the calculated free energy changes are below the value of À5 kcal/mol (the ''rule of thumb'') [53]. These data can be taken as proofs that photoelectron transfer process occurs between the quenchers and sensitizer molecules and contact radical ion pairs are generated.…”

Section: Measurements and Fluorescence Quenching Experimentsmentioning

confidence: 72%

New thiophene-based azo ligands containing azo methine group in the main chain for the determination of copper(II) ions

et al. 2007

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Section: Measurements and Fluorescence Quenching Experimentsmentioning

confidence: 72%

New thiophene-based azo ligands containing azo methine group in the main chain for the determination of copper(II) ions

et al. 2007

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“…The RFI value of 1f, with the strongest electron-withdrawing nitro group, was comparable with that of 1b, with an electron-donating methyl group. This prominent decrease in 1f may be attributed to the nonemissive twisted ICT (TICT) excited state, [39][40][41][42][43] where push-pull p-electron systems between a methoxyl group at the 6-position and a nitro group at the 3-position in a molecule must be fully separated in polar solvent such as acetonitrile. Rettig and Klock reported that the very weak fluorescence of 6-aminocoumarin with a stronger electron-donating amino group than the methoxyl group was attributed to this TICT between the amino group and coumarin ring.…”

Section: Resultsmentioning

confidence: 99%

Improvement of Fluorescence Characteristics of Coumarins: Syntheses and Fluorescence Properties of 6-Methoxycoumarin and Benzocoumarin Derivatives as Novel Fluorophores Emitting in the Longer Wavelength Region and Their Application to Analytical Reagents

Murata

Masuda

Kamochi

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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Fluorometric analysis is one of the most sensitive methods for detecting organic and/or inorganic compounds and therefore it has been widely used in many scientific fields with improving analytical instruments such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), fluorescence confocal microscopy, etc. For these purposes, a great deal of effort has gone into the development of fluorescent reagents using various fluorophores, which can be utilized for derivatizing biologically active small molecules, labeling macromolecules such as proteins and DNAs, and probing ions such as biologically relevant metal cations and inorganic or organic anions. [1][2][3][4] In the development of such fluorescent reagents, it should first be ensured that the fluorophore used has a high fluorescence quantum yield because of the reliably high sensitivity in the detection. Fluorescein is one of the most widely used fluorophore for biological experiments, since it has a high fluorescence quantum yield of 0.90 or grater in aqueous solution and its excitation and emission wavelengths are in the visible region. Recently, Nagano and coworkers have succeeded in developing fluorescent reagents for the specific detection of nitric oxide (NO), [5][6][7][8] singlet oxygen ( 1 O 2 ), 9,10) and others 11,12) using fluorescein as the fluorophore. 4,4-Difluoro-4-bora-3a,4a-diazas-indacenes (BODIPYs) are also well-known fluorophores that have very sharp and narrow fluorescence bandwidths in addition to their high fluorescence quantum yield in aqueous solution. 4,13,14) Therefore they have been used as mother fluorophores for many analytical purposes. [15][16][17][18] However, the difference between the excitation and emission wavelengths of these derivatives are very small, less than approximately 30 nm for fluoresceins and 15 nm for BODIPYs, and it is necessary to correct their spectra from interferences such as Rayleigh or Raman scattering light.On the other hand, coumarin (2H-benzopyran-2-one), is also another interesting fluorophore, since its fluorescence changes drastically with substituents and their introduced positions. [19][20][21] In previous papers, we reported the fluorescence characteristics of methoxycoumarins and discussed the structural features of strongly fluorescing methoxycoumarins from the viewpoint of intramolecular charge transfer (ICT) between push-and pull-substituents in the ground and the excited states.22,23) Based on the above findings, we succeeded in developing novel fluorescent reagents with both high sensitivity and functions such as self-catalytic reactivity. [24][25][26] In the course of those studies, we suspected that most coumarin derivatives showed large Stokes shifts in their fluorescence spectra as compared with other fluorophores. These large Stokes shifts appear to be advantageous for escaping autofluorescence from biological molecules and reducing the self-absorption of chromophores. Further, if the emission bands of coumarins could be shifted to longer wavelengths with larg...

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“…The oxidation potentials of the amines ͕E(A/A ϩ )͖ in TX100 micellar solutions were estimated from the reported values in acetonitrile solutions after applying a suitable correction for the micellar media. [47][48][49][50] …”

Section: Methodsmentioning

confidence: 99%

Intermolecular electron transfer between coumarin dyes and aromatic amines in Triton-X-100 micellar solutions: Evidence for Marcus inverted region

Kumbhakar

Nath

Mukherjee

et al. 2004

The Journal of Chemical Physics

155

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Photoinduced electron transfer (ET) between coumarin dyes and aromatic amines has been investigated in Triton-X-100 micellar solutions and the results have been compared with those observed earlier in homogeneous medium. Significant static quenching of the coumarin fluorescence due to the presence of high concentration of amines around the coumarin fluorophore in the micelles has been observed in steady-state fluorescence studies. Time-resolved studies with nanosecond resolutions mostly show the dynamic part of the quenching for the excited coumarin dyes by the amine quenchers. A correlation of the quenching rate constants, estimated from the time-resolved measurements, with the free energy changes (DeltaG0) of the ET reactions shows the typical bell shaped curve as predicted by Marcus outer-sphere ET theory. The inversion in the ET rates for the present systems occurs at an exergonicity (-DeltaG0) of approximately 0.7-0.8 eV, which is unusually low considering the polarity of the Palisade layer of the micelles where the reactants reside. Present results have been rationalized on the basis of the two dimensional ET model assuming that the solvent relaxation in micellar media is much slower than the rate of the ET process. Detailed analysis of the experimental data shows that the diffusional model of the bimolecular quenching kinetics is not applicable for the ET reactions in the micellar solutions. In the present systems, the reactions can be better visualized as equivalent to intramolecular electron transfer processes, with statistical distribution of the donors and acceptors in the micelles. A low electron coupling (Vel) parameter is estimated from the correlation of the experimentally observed and the theoretically calculated ET rates, which indicates that the average donor--acceptor separation in the micellar ET reactions is substantially larger than for the donor--acceptor contact distance. Comparison of the Vel values in the micellar solution and in the donor--acceptor close contact suggests that there is an intervention of a surfactant chain between the interacting donor and acceptor in the micellar ET reaction.

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Electron donor-acceptor quenching and photoinduced electron transfer for coumarin dyes

Cited by 88 publications

References 1 publication

New thiophene-based azo ligands containing azo methine group in the main chain for the determination of copper(II) ions

New thiophene-based azo ligands containing azo methine group in the main chain for the determination of copper(II) ions

Improvement of Fluorescence Characteristics of Coumarins: Syntheses and Fluorescence Properties of 6-Methoxycoumarin and Benzocoumarin Derivatives as Novel Fluorophores Emitting in the Longer Wavelength Region and Their Application to Analytical Reagents

Intermolecular electron transfer between coumarin dyes and aromatic amines in Triton-X-100 micellar solutions: Evidence for Marcus inverted region

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