Influence of an Intermolecular Charge-Transfer State on Excited-State Relaxation Dynamics: Solvent Effect on the Methylnaphthalene−Oxygen System and its Significance for Singlet Oxygen Production

Jensen, Peter D. Ørberg; Arnbjerg, J.; Tolbod, Lars Poulsen; Toftegaard, Rasmus; Ogilby, Peter R.

doi:10.1021/jp905728d

Cited by 39 publications

(55 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…26,59 Moreover, electron-rich and easilyoxidized species facilitate the formation of charge-transfer states upon interaction with O 2 (a 1  g ), which promotes the nonradiative deactivation of O 2 (a 1  g ) to O 2 (X 3  g -). 26,60 With this interpretation in mind, the pD-dependent values of k rem shown in Table 1 are consistent with revised pKa values of bilirubin that have recently been published. 61 The data also clearly show that encapsulating bilirubin in the UnaG protein results in an appreciable decrease in the magnitude of k rem .…”

Section: Overall Bilirubin- Apounag- and Holounag-mediated O 2 (A 1supporting

confidence: 87%

Protein-encapsulated bilirubin: paving the way to a useful probe for singlet oxygen

Pimenta

Jensen

Etzerodt

et al. 2015

Photochem Photobiol Sci

Self Cite

View full text Add to dashboard Cite

When dissolved in a bulk solvent, bilirubin efficiently removes singlet molecular oxygen, O2(a(1)Δg), through a combination of chemical reactions and by promoting the O2(a(1)Δg)→O2(X(3)Σg(-)) nonradiative transition to populate the ground state of oxygen. To elucidate how such processes can be exploited in the development of a biologically useful fluorescent probe for O2(a(1)Δg), pertinent photophysical and photochemical parameters of bilirubin encapsulated in a protein were determined. The motivation for studying a protein-encapsulated system reflects the ultimate desire to (a) use genetic engineering to localize the probe at a specific location in a living cell, and (b) provide a controlled environment around the chromophore/fluorophore. Surprisingly, explicit values of oxygen- and O2(a(1)Δg)-dependent parameters that characterize the behavior of a given chromophore/fluorophore encased in a protein are not generally available. To the end of quantifying the effects of such an encasing protein, a recently discovered bilirubin-binding protein isolated from a Japanese eel was used. The data show that this system indeed preferentially responds to O2(a(1)Δg) and not to the superoxide ion. However, this protein not only shields bilirubin such that the rate constants for interaction with O2(a(1)Δg) decrease relative to what is observed in a bulk solvent, but the fraction of the total O2(a(1)Δg)-bilirubin interaction that results in a chemical reaction between O2(a(1)Δg) and bilirubin also decreases appreciably. The rate constants thus obtained provide a useful starting point for the general design and development of reactive protein-encased fluorescent probes for O2(a(1)Δg).

show abstract

Section: Overall Bilirubin- Apounag- and Holounag-mediated O 2 (A 1supporting

confidence: 87%

Protein-encapsulated bilirubin: paving the way to a useful probe for singlet oxygen

Pimenta

Jensen

Etzerodt

et al. 2015

Photochem Photobiol Sci

Self Cite

View full text Add to dashboard Cite

show abstract

“…We assume that, as with many other organic molecules, M, channel 3 can become more probable by virtue of a process that introduces charge-transfer character into the M-O 2 collision complex. [12] In summary, data recorded from selected b-carbolines provide sufficient evidence that, upon oxygen quenching of the fluorescent state, O 2 -induced S 1 !S 0 internal conversion can indeed efficiently compete with O 2 -induced S 1 !T 1 intersystem crossing. Although the reasons for this phenomenon currently remain unsolved, it is likely that systematic experiments will now reveal other molecules that also provide an "exception to the rule".…”

Section: à3mentioning

confidence: 84%

Fluorescence Quenching by Oxygen: “Debunking” a Classic Rule

et al. 2010

Self Cite

View full text Add to dashboard Cite

It has long been accepted that oxygen-induced deactivation of an organic molecule's fluorescent state (i.e. the lowest excited singlet state, S 1 ) proceeds exclusively via intersystem crossing (ISC) to produce the triplet excited state, T 1 . [1][2][3][4] Oxygeninduced S 1 !S 0 internal conversion (IC) to produce the singlet ground state, S 0 , is thought not to occur. In a light-filled world where S 1 generation is commonplace and where molecular oxygen can be found at appreciable concentrations, this phenomenon can have significant implications. Among other things, it means that much O 2 -dependent photochemistry derives from the T 1 state and, as such, can yield unique and characteristic products.To our knowledge, only 9,10-diphenylanthracene has been presented as an exception to the rule that O 2 always induces S 1 !T 1 ISC.[5] Even in this case, however, the data are not as convincing as one might otherwise desire. We recently suggested that b-carbolines, bCs, may provide substantive evidence that an O 2 -induced S 1 !S 0 transition can actually occur. [6] We now demonstrate that the O 2 -dependent photophysics of selected bCs indeed provide an "exception to the rule" and that O 2 -induced S 1 !S 0 IC can efficiently compete with O 2 -induced S 1 !T 1 ISC. The present data, point to the possibility that other molecules will respond to O 2 like the bCs, limiting T 1 -derived chemistry or behavior which, in turn, opens new options for the design and application of unique photochemical, photophysical, and photobiological systems.The bCs used, norharmane (nHo, R 1 = R 2 = H), harmane (Ho, R 1 = H, R 2 = CH 3 ) and N-methylharmane (NMeHo, R 1 = R 2 = CH 3 ), Scheme 1, are water soluble compounds of significant biological importance whose behavior depends on pH.[6] Although the S 1 !S 0 phenomenon presented herein is observed in both alkaline and acidic media, it is more pronounced in the latter and, as such, we limit our discussion to data recorded at pH 5. We also limit our discussion to Ho; data for nHo and NMeHo can be found in the Supporting Information.For Ho, the fluorescence quantum yield, F F , decreases as the concentration of dissolved oxygen increases (Figure 1 a). This is expected with the bimolecular quenching of S 1 by O 2 . Indeed, these compounds have an S 1 lifetime (~20-25 ns) [6][7][8] that is long enough for O 2 -induced deactivation to play a prominent role.If O 2 indeed induces S 1 !T 1 ISC, one would then expect to see a corresponding increase in the triplet state yield. This was not the case. Rather, we observed a distinct and pronounced decrease in the T 1 yield as the O 2 concentration was increased (Figure 1 b). The latter data were recorded in time-resolved ab- [a] Dr.

show abstract

“…In turn, this results in a k phys / k chem ratio for Oregon Green that is over 10 times greater than that for Athens Green. Of the postulated mechanisms for solute-mediated O 2 (a 1 Δ g ) deactivation to O 2 (X 3 Σ g − ), processes that occur with rate constants of ~10 6 –10 7 s −1 M −1 , as we have for these fluoresceins, focus on the role played by the oxygen-quencher charge-transfer (CT) state [ 47 , 48 , 49 , 50 ]. The thesis is that, for a compound M that can better donate charge to oxygen, the M +.…”

Section: Resultsmentioning

confidence: 99%

Oxygen- and pH-Dependent Photophysics of Fluorinated Fluorescein Derivatives: Non-Symmetrical vs. Symmetrical Fluorination

McLoughlin

Kotroni

Bregnhøj

et al. 2020

Sensors

Self Cite

View full text Add to dashboard Cite

Fluorescein, and derivatives of fluorescein, are often used as fluorescent probes and sensors. In systems where pH is a variable, protonation/deprotonation of the molecule can influence the pertinent photophysics. Fluorination of the xanthene moiety can alter the molecule’s pKa such as to render a probe whose photophysics remains invariant over a wide pH range. Di-fluorination is often sufficient to accomplish this goal, as has been demonstrated with compounds such as Oregon Green in which the xanthene moiety is symmetrically difluorinated. In this work, we synthesized a non-symmetrical difluorinated analog of Oregon Green which we call Athens Green. We ascertained that the photophysics and photochemistry of Athens Green, including the oxygen-dependent photophysics that results in the sensitized production of singlet oxygen, O2(a1Δg), can differ appreciably from the photophysics of Oregon Green. Our data indicate that Athens Green will be a more benign fluorescent probe in systems that involve the production and removal of O2(a1Δg). These results expand the available options in the toolbox of fluorescein-based fluorophores.

show abstract

Influence of an Intermolecular Charge-Transfer State on Excited-State Relaxation Dynamics: Solvent Effect on the Methylnaphthalene−Oxygen System and its Significance for Singlet Oxygen Production

Cited by 39 publications

References 54 publications

Protein-encapsulated bilirubin: paving the way to a useful probe for singlet oxygen

Protein-encapsulated bilirubin: paving the way to a useful probe for singlet oxygen

Fluorescence Quenching by Oxygen: “Debunking” a Classic Rule

Oxygen- and pH-Dependent Photophysics of Fluorinated Fluorescein Derivatives: Non-Symmetrical vs. Symmetrical Fluorination

Contact Info

Product

Resources

About