Reasons for the difference between the rate constant of quenching of the triplet state and the diffusion rate constant of chlorophyll-like molecules

1989 ◽  
Vol 50 (1) ◽  
pp. 94-99
Author(s):  
V. V. Sapunov
Keyword(s):  
Triplet State ◽  
Rate Constant ◽  
Diffusion Rate ◽  
Diffusion Rate Constant ◽  
The Difference

Diffusional Fluorescence Quenching of Aromatic Hydrocarbons

2003 ◽  
Vol 57 (5) ◽  
pp. 538-544 ◽  
Author(s):  
Clelia Canuel ◽  
Sophie Badre ◽  
Henning Groenzin ◽  
Markus Berheide ◽  
Oliver C. Mullins
Keyword(s):  
Fluorescence Quenching ◽  
Molecular Oxygen ◽  
Rate Constant ◽  
Aromatic Hydrocarbons ◽  
Diffusion Rate ◽  
Energy Difference ◽  
Quenching Rate ◽  
Quenching Rate Constant ◽  
Diffusion Rate Constant ◽  
Organic Fluorophore

The quenching of the fluorescence of five aromatic hydrocarbons by three halogenated organics and by molecular oxygen has been measured. Both fluorescence intensity and fluorescence lifetime measurements have been employed to validate results and interpretation; linear Stern–Volmer analyses are shown to apply throughout. The fluorescence quenching rate constant of molecular oxygen for the five aromatic hydrocarbons is essentially equivalent to the diffusion rate constant independent of the fluorophore excitation energy. The halogenated organic–fluorophore rate constants vary by a factor of 965 and are shown to correlate roughly with the energy difference between the quencher and fluorophore excited electronic states in accord with a standard model of quantum two-level mixing. The value of the coupling interaction energy is ∼2500 cm−1.

scholarly journals Characterization of hydroxybenzoic acid chelating resins: Equilibrium, kinetics, and isotherm profiles for Cd(II) and Pb(II) uptake

2011 ◽  
Vol 76 (6) ◽  
pp. 903-922 ◽  
Author(s):  
Bhavna Shah ◽  
Ajay Shah ◽  
Ritesh Tailor
Keyword(s):  
Rate Constant ◽  
Metal Ion ◽  
Diffusion Rate ◽  
Ion Concentration ◽  
Particle Diffusion ◽  
Specific Rate ◽  
Hydroxybenzoic Acid ◽  
Sorption Data ◽  
Intra Particle Diffusion ◽  
Diffusion Rate Constant

Chelating ion-exchange resins were synthesized by polycondensation of ortho/para hydroxybenzoic acid with resorcinol/catechol employing formaldehyde as cross-linking agent at 80?5?C in DMF. The resins were characterized by FTIR and XRD. The uptake behaviour of synthesized resins for Cd(II) and Pb(II) ions have been studied depending on contact time, pH, metal ion concentration and temperature. The sorption data obtained at optimized conditions were analyzed by the Langmuir and Freundlich isotherms. Experimental data of all metal-resin system were best represented by the Freundlich isotherm. The maximum obtained sorption capacity for cadmium was 69.53 mg g-1 and 169.32 mg g-1 for Lead. The adsorption process follows first order kinetics and the specific rate constant Kr was obtained by the application of the Lagergan equation. Thermodynamic parameters ?Gads, ?Sads and ?Hads were calculated for the metal-resin systems. The external diffusion rate constant (Ks) and the intra-particle diffusion rate constant (Kid) were calculated by the Spahn-Schlunder and Weber-Morris models, respectively. The sorption process was found to follow an intra-particle diffusion phenomenon.

The acid-catalyzed demetalation of 1-(tri-n-butylstannyl)-2-phenylethyne. A surprisingly small β-stannyl effect

1996 ◽  
Vol 74 (7) ◽  
pp. 1366-1368 ◽  
Author(s):  
I. Egle ◽  
V. Gabelica ◽  
A.J. Kresge ◽  
T.T. Tidwell
Keyword(s):  
Key Words ◽  
Isotope Effect ◽  
Acid Concentration ◽  
Rate Constant ◽  
Perchloric Acid ◽  
Hydronium Ion ◽  
Stabilizing Effect ◽  
Aromatic Product ◽  
Acid Catalyzed ◽  
The Difference

Rates of conversion of 1-(tri-n-butylstannyl)-2-phenylethyne to phenylethyne in H2O and D2O solutions of perchloric acid were found to be proportional to acid concentration, giving the hydronium ion rate constant [Formula: see text] and the isotope effect [Formula: see text]. The magnitude of this isotope effect suggests that the reaction occurs by rate-determining hydron transfer to the substrate, producing a vinyl carbocation; this carbocation then loses its tributylstannyl group, giving phenylacetylene as the only detectable aromatic product. The hydronium ion rate constant, when compared to the rates of protonation of phenylethyne and 1-(trimethylsilyl)-2-phenylethyne, gives a β-stannyl stabilizing effect of δΔG≠ = 6.6 kcal mol−1 and a differential β-stannyl/β-silyl effect of δΔG≠ = 3.2 kcal mol−1. These stabilizations are very much smaller than previously reported β-stannyl effects. Possible reasons for the difference are suggested. Key words: β-stannyl effect, β-silyl effect, carbocation stabilization, protodemetalation.

Detection and chemistry of the triplet state of thymine

1970 ◽  
Vol 48 (4) ◽  
pp. 694-696 ◽  
Author(s):  
A. G. Szabo ◽  
W. D. Rlddell ◽  
R. W. Yip
Keyword(s):  
Excited State ◽  
Triplet State ◽  
Rate Constant ◽  
Triplet Excited State

The transient produced on flash excitation of degassed solutions of thymine in acetonitrile has been characterized as the triplet excited state of thymine. This triplet state has a lifetime of 14 ± 1 μs and the associated dimerization rate was found to be 5.3 ± 0.3 × 108 M−1 s−1. The triplet state of thymine could be quenched by 2,4-hexadien-1-ol with a rate constant of 8.1 ± 0.6 × 109 M−1 s−1.

Phenyl Substitution Effects on Triplet–Triplet Absorption Spectra: I. Study of 1,3,6,8-Tetraphenylpyrene

1975 ◽  
Vol 53 (21) ◽  
pp. 3269-3275 ◽  
Author(s):  
C. Rullière ◽  
E. C. Colson ◽  
P. C. Roberge
Keyword(s):  
Absorption Spectrum ◽  
Triplet State ◽  
Absorption Spectra ◽  
Rate Constant ◽  
Theoretical Calculations ◽  
Vibrational Structure ◽  
Substitution Effects ◽  
Quenching Rate ◽  
Diffusion Controlled ◽  
Quenching Rate Constant

The triplet–triplet (T–T) absorption spectrum of 1,3,6,8-tetraphenylpyrene (TPP) was measured from 400 to 620 nm. The data obtained are compared with theoretical calculations using the Ruedenberg–Scherr FEMO model. A planar triplet state is evidenced by fine vibrational structure. The T–T quenching rate constant measured (1.3 ± 0.1 × 109 M−1 s−1) is 20% of the expected diffusion-controlled value.

A reinvestigation of the interaction between triplet states of cyclohexenones and amines

1988 ◽  
Vol 66 (10) ◽  
pp. 2595-2600 ◽  
Author(s):  
D. Weir ◽  
J. C. Scaiano ◽  
D. I. Schuster
Keyword(s):  
Triplet State ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Radical Cations ◽  
Laser Flash ◽  
Triplet States ◽  
New Evidence

Laser flash photolysis studies lead to the conclusion that the short-lived triplet states of cyclohexenones are readily quenched by amines. For example, in the case of 2-cyclohexen-1-one (1) its triplet state (τT = 40 ns in acetonitrile) is quenched by triethylamine with a rate constant of (9.0 ± 0.8) × 107 M−1 s−1. Cyclohexenone triplets are also quenched efficiently by DABCO and by triphenylamine leading to the formation of the corresponding amine radical cations. The new evidence reported rules out the involvement of long-lived detectable exciplexes.

Lifetime and quenching rate constant for the lowest triplet state of sulfur dioxide

1970 ◽  
Vol 92 (1) ◽  
pp. 217-218 ◽  
Author(s):  
Susan S. Collier ◽  
Akira. Morikawa ◽  
David H. Slater ◽  
Jack G. Calvert ◽  
George. Reinhardt ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Triplet State ◽  
Rate Constant ◽  
Quenching Rate ◽  
Quenching Rate Constant
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