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Michael Y. Ogawa - One of the best experts on this subject based on the ideXlab platform.
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The localization of hydrophilic sites within an osmium polypyridyl compound can produce a Negative Activation Energy for emission decay
Inorganic Chemistry Communications, 2001Co-Authors: Anula Ranatunga, Robin C. Lasey, Michael Y. OgawaAbstract:Abstract The temperature dependence of the emission lifetimes of two structural isomers of an osmium polypyridyl complex are reported. The compounds [Os(bpy) 2 (4,4 ′ -dcbpy)] ( 1 ) and [Os(bpy) 2 (3,5-dcbpy)] ( 2 ), where 4,4 ′ -dcbpy=4,4 ′ -dicarboxy-2,2 ′ -bipyridine and 3,5-dcbpy=3,5-dicarboxy-2,2 ′ -bipyridine, differ only in the placement of their two hydrophilic carboxylate groups within the unique bipyridine ligand. In argon-saturated water, the emission life-time of 1 decreases with increasing temperature and can be fit to the Arrhenius expression (k obs =k 0 exp (−E a /RT)) to give values of k 0 =(2.6±0.3)×10 8 s −1 and E a =+330±20 cm −1 . In contrast the emission of 2 measured in ethanol displays longer lifetimes at higher temperatures to give k 0 =(2.9±0.3)×10 6 s −1 and E a =−590±20 cm −1 . Thus, the specific localization of the hydrophilic carboxylate groups in these molecules significantly alters their photophysical properties and can produce Negatively activated emission lifetimes.
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a Negative Activation Energy for luminescence decay specific solvation effects on the emission properties of bis 2 2 bipyridine 3 5 dicarboxy 2 2 bipyridine ruthenium ii chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
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A Negative Activation Energy for Luminescence Decay: Specific Solvation Effects on the Emission Properties of Bis(2,2‘-bipyridine)(3,5-dicarboxy-2,2‘-bipyridine)ruthenium(II) Chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
M. J. Rossi - One of the best experts on this subject based on the ideXlab platform.
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The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
Atmospheric Chemistry and Physics, 2003Co-Authors: C. Delval, B. Fluckiger, M. J. RossiAbstract:Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small Negative Activation Energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3?6 and 10?20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.
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The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles
Atmospheric Chemistry and Physics Discussions, 2003Co-Authors: C. Delval, B. Fluckiger, M. J. RossiAbstract:Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6×1028+/?1·exp({?10.3+\?1.2}/{RT}) [molec cm?2 s?1], kcond=1.7×10?2+\-1×exp({+1.6+\?1.5}/{RT}) [s?1], in the presence of an HCl mole fraction in the range 3.2×10?5-6.4×10?3: Jev=6.4×1026+/?1×exp({?9.7+/?1.2}/{RT}) [molec cm?2 s?1], kcond=2.8×10?2+/-1×exp({+1.5+/?1.6}/{RT}) [s?1], and an HBr mole fraction smaller than 6.4×10?3:Jev=7.4×1025+/?1×exp({?9.1+/?1.2}/{RT}) [molec cm?2 s?1], kcond=7.1×10?5+\?1×exp({+2.6+/?1.5}/{RT}) [s?1]}. The small Negative Activation Energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/?2.7 kcal mol?1, DHsubl=11.2+/?2.8 kcal mol?1, and DHsubl=11.7+/?2.8 kcal mol?1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol?1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3?6 and 10?20, respectively, for submonolayer coverages of HX.
S. R. L. Fernando - One of the best experts on this subject based on the ideXlab platform.
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a Negative Activation Energy for luminescence decay specific solvation effects on the emission properties of bis 2 2 bipyridine 3 5 dicarboxy 2 2 bipyridine ruthenium ii chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
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A Negative Activation Energy for Luminescence Decay: Specific Solvation Effects on the Emission Properties of Bis(2,2‘-bipyridine)(3,5-dicarboxy-2,2‘-bipyridine)ruthenium(II) Chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
C. Delval - One of the best experts on this subject based on the ideXlab platform.
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The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles
Atmospheric Chemistry and Physics, 2003Co-Authors: C. Delval, B. Fluckiger, M. J. RossiAbstract:Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp (- 10.3 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp (- 9.7 ± 1.2/ RT) [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT) [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT) [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small Negative Activation Energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3?6 and 10?20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.
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The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: Implications for the lifetime of atmospheric ice particles
Atmospheric Chemistry and Physics Discussions, 2003Co-Authors: C. Delval, B. Fluckiger, M. J. RossiAbstract:Using a multidiagnostic approach the rate Rev or flux Jevof evaporation of H2O and its condensation, kcond, on a 1mm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions with RT in kcal mol-1 for pure ice are Jev=1.6×1028+/?1·exp({?10.3+\?1.2}/{RT}) [molec cm?2 s?1], kcond=1.7×10?2+\-1×exp({+1.6+\?1.5}/{RT}) [s?1], in the presence of an HCl mole fraction in the range 3.2×10?5-6.4×10?3: Jev=6.4×1026+/?1×exp({?9.7+/?1.2}/{RT}) [molec cm?2 s?1], kcond=2.8×10?2+/-1×exp({+1.5+/?1.6}/{RT}) [s?1], and an HBr mole fraction smaller than 6.4×10?3:Jev=7.4×1025+/?1×exp({?9.1+/?1.2}/{RT}) [molec cm?2 s?1], kcond=7.1×10?5+\?1×exp({+2.6+/?1.5}/{RT}) [s?1]}. The small Negative Activation Energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl=Eev-Econd=11.9+/?2.7 kcal mol?1, DHsubl=11.2+/?2.8 kcal mol?1, and DHsubl=11.7+/?2.8 kcal mol?1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol?1. Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3?6 and 10?20, respectively, for submonolayer coverages of HX.
Thomas H. Kinstle - One of the best experts on this subject based on the ideXlab platform.
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a Negative Activation Energy for luminescence decay specific solvation effects on the emission properties of bis 2 2 bipyridine 3 5 dicarboxy 2 2 bipyridine ruthenium ii chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
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A Negative Activation Energy for Luminescence Decay: Specific Solvation Effects on the Emission Properties of Bis(2,2‘-bipyridine)(3,5-dicarboxy-2,2‘-bipyridine)ruthenium(II) Chloride
Journal of the American Chemical Society, 1996Co-Authors: S. R. L. Fernando, U. S. M. Maharoof, Kurt D. Deshayes, Thomas H. Kinstle, Michael Y. OgawaAbstract:A new mixed-ligand polypyridylruthenium(II) complex, [Ru(bpy)2L]Cl2, has been prepared where bpy = 2,2‘-bipyridine and L = 3,5-dicarboxy-2,2‘-bipyridine. The ligand L is a non-symmetrically-substituted 2,2‘-bipyridine having two hydrophilic carboxylate groups located at the 3- and 5-positions of only one of its two pyridyl rings. In acetonitrile, the photophysical properties of the metal complex include a long-lived excited state (λem = 637 nm, τ = 846 ± 11 ns, φ = 0.046 at 295 K) whose decay involves an activated crossing to higher Energy ligand field states (Ea = 4170 ± 200 cm-1). This behavior is similar to that observed for other ruthenium tris(bipyridyl) compounds. In contrast, the title compound displays several unusual photophysical properties in aqueous solution. These include a strongly red-shifted emission (λem = 685 nm) having a short, pH-dependent lifetime which is quenched by an excited-state proton transfer from solvent. The completely deprotonated form of the molecule is the dominant emissi...
