Excited-state proton transfer from pyranine to acetate in methanol

Mondal, Sudip Kumar; Ghosh, Subhadip; Sahu, Kalyanasis; Sen, Pratik; Bhattacharyya, Kankan

doi:10.1007/s12039-007-0012-x

Cited by 26 publications

(17 citation statements)

References 16 publications

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“…Ground-and excited-state proton transfers have become important from the mechanistic point of view. [1][2][3][4][5][6] Single and double proton transfer probes are quite well known and serve as important and interesting means to discover many chemical and biological consequences. For a long time, double proton transfer (DPT) has drawn the attention of many in the scientific world.…”

Section: Introductionmentioning

confidence: 99%

Promoting the “water-wire” mechanism of double proton transfer in [2,2′-bipyridyl]-3,3′-diol by porous gold nanoparticles

Nag

Das

Mondal

et al. 2015

Phys. Chem. Chem. Phys.

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The effect of nanopores in porous gold nanoparticles (Au NPs) on excited-state double proton transfer (DPT) in [2,2'-bipyridyl]-3,3'-diol (BP(OH)2) in an aqueous environment is the main focus of the present work. DPT in BP(OH)2 is known to take place through two mechanisms. In a bulk environment, an open solvated molecule facilitates the process and emits at 460 nm whereas, in a confined situation, formation of a "water wire" between the prototropic centers leads to the transfer of protons. It has been shown spectroscopically in the present study that in the nanovessels provided by nanoporous Au NPs, the unconventional mechanism of DPT through the formation of a "water wire" is promoted due to the presence of a limited number of water molecules around the probe. Experiments in the presence of solid pure Au, Ag and Au/Ag NPs were performed to support our proposition. Time-resolved fluorescence spectral changes confirm our findings.

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Section: Introductionmentioning

confidence: 99%

Promoting the “water-wire” mechanism of double proton transfer in [2,2′-bipyridyl]-3,3′-diol by porous gold nanoparticles

Nag

Das

Mondal

et al. 2015

Phys. Chem. Chem. Phys.

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“…8,[23][24][25][26][27][28][29] Another paradigmatic photoacid is 8-hydroxypyrene-1,3,6-trisulfonate (HPTS, pyranine), which exhibits absorption and emission in the visible part of the electromagnetic spectrum and a high water solubility. 13,[30][31][32][33][34][35][36] ESPT of these photoacids to bases 32,37 or the solvent [38][39][40] has been reported. In most examples, the proton-accepting solvent is water because of its high polarity and unique tendency to accept and stabilize protons in a hydrogen-bonding network.…”

Section: Introductionmentioning

confidence: 99%

Solvatochromism of pyranine-derived photoacids

Spies

Finkler

Açar

et al. 2013

Phys. Chem. Chem. Phys.

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Photoacidity is frequently found in aromatic alcohols where the equilibrium dissociation constant increases by some orders of magnitude upon electronic excitation. In this study we investigated the solvatochromism of a family of recently synthesized super-photoacids and their methylated counterparts based on pyrene. The chemical similarity of these molecules on the one hand and their differing photoacidity with pKa* values between -0.8 and -3.9 on the other allow for gaining insights into the mechanisms contributing to excited-state proton transfer. Three different solvent scales, namely Lippert-Mataga, Kamlet-Taft and Catalán, were independently employed in this study and gave consistent results. We found the strongest correlation of the excited-state acidity with the dipolarity of the excited state, pem ranging from -1775 cm(-1) to -2500 cm(-1), and a concomitant change in the permanent dipole moment of roughly 14 Debye. Spectral changes due to varying basicity of the solvent, which probes the conjugated property of the solute, are found to be less indicative of the graduation of excited-state acidity, i.e. bem values between -700 and -1200 cm(-1). The solvent acidity is the only parameter with a distinct influence on the electronic spectra of the deprotonated species. The low values of aem ~ 400 cm(-1), which are 3-4× smaller than aabs and aexc, indicate the low basicity of these species in the excited state. Triggered by semiempirical theoretical calculations, the energetic splitting between the two lowest excited states could be related to the excited-state acidity and points to alterations in the electronic mixing of locally excited and charge-transfer states, caused by the substituents. Differences between the threefold negatively charged pyranine and the new neutral photoacids are also discussed.

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“…This time constant is very similar to the slower component of the decay of the protonated emission observed at 425 nm and may be assigned to the lifetime of HPTS inside the interface of the DDAB reverse micelle. Note that the lifetime is quite short compared to the lifetime of HPTS in water (∼5.5 ns) but close to the lifetime of HPTS in methanol (4 ns) . The TRANES at w 0 = 2 do not show much variation with time except a very small spectral shift of the protonated emission band and very small contribution of deprotonated emission appears at long time (≥7 ns).…”

Section: Resultsmentioning

confidence: 63%

“…Note that the lifetime is quite short compared to the lifetime of HPTS in water (∼5.5 ns) but close to the lifetime of HPTS in methanol (4 ns). 43 The TRANES at w 0 = 2 do not show much variation with time except a very small spectral shift of the protonated emission band and very small contribution of deprotonated emission appears at long time (≥7 ns). Thus, ESPT process is very insignificant at this w 0 .…”

Section: Resultsmentioning

confidence: 93%

How Does Interfacial Hydration Alter during Rod to Sphere Transition in DDAB/Water/Cyclohexane Reverse Micelles? Insights from Excited State Proton Transfer and Fluorescence Anisotropy

2016

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How does microscopic organization of an organized assembly alter during macroscopic structural transition? The question may be important to ascertain driving forces responsible for such transitions. Didodecyldimethylammonium bromide (DDAB)/water/cyclohexane reverse micelle is an attractive assembly that undergoes structural transition from rod to spherical shape when the amount of water loading, w0 ([water]/[surfactant]), exceeds a particular value (w0 ∼ 8). Here, we intend to investigate the effect of the morphological change upon interfacial hydration using steady-state and time-resolved fluorescence measurements. The anionic fluorophore 8-hydroxypyrene-1,3,6-trisulfonate (HPTS or pyranine) is expected to be trapped within the positively charged RM interface. The fluorophore can undergo excited-state proton transfer (ESPT) in the presence of water and, thus, is able to provide insight on the level of hydration within the interface. The ESPT process is markedly inhibited within the interface at low w0 and gradually favored with increase of w0. The time-resolved fluorescence decays could be best analyzed by assuming distribution of HPTS over two distinct interfacial regions- partly hydrated and mostly dehydrated. The relative population of the two regions varies distinctly at low w0 (<6) and high w0 (>6) regimes. Moreover, fluorescence anisotropy (steady-state and time-resolved) varies differently with respect to w0, before and after the transition point (w0 ∼ 8).

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Excited-state proton transfer from pyranine to acetate in methanol

Cited by 26 publications

References 16 publications

Promoting the “water-wire” mechanism of double proton transfer in [2,2′-bipyridyl]-3,3′-diol by porous gold nanoparticles

Promoting the “water-wire” mechanism of double proton transfer in [2,2′-bipyridyl]-3,3′-diol by porous gold nanoparticles

Solvatochromism of pyranine-derived photoacids

How Does Interfacial Hydration Alter during Rod to Sphere Transition in DDAB/Water/Cyclohexane Reverse Micelles? Insights from Excited State Proton Transfer and Fluorescence Anisotropy

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