Studies in mixed solvents: Comparison between solvated electron reactions and quenching of excited states

1995 ◽  
Vol 27 (6) ◽  
pp. 535-545 ◽  
Author(s):  
Sudhir Kumar Kapoor ◽  
C. Gopinathan
Keyword(s):  
Excited States ◽  
Mixed Solvents ◽  
Solvated Electron

Thermostable sites of palladium phthalocyanine in Shpol'skii matrices of mixed solvents

1984 ◽  
Vol 62 (11) ◽  
pp. 2264-2272 ◽  
Author(s):  
Wen-Hsiung Chen ◽  
Klaus E. Rieckhoff ◽  
Eva-Maria Voigt
Keyword(s):  
Excited States ◽  
Mixed Solvent ◽  
Mixed Solvents ◽  
Dipolar Interaction ◽  
Site Formation ◽  
Effective Mechanism ◽  
Large Molecules ◽  
Clear Guideline ◽  
Vibrational Features ◽  
Insight Into

A study was made of the effects of three different mixed solvent Shpol'skii matrices at 4.2 K on site formation and on vibronic progressions of palladium phthalocyanine. It is found that only a limited number of thermostable sites are formed and these sites are common to all three matrices, but vary in their statistical weights. However, in all solvents the statistical weights of the first few most important sites are similar, with the predominant site at least eight or nine times stronger than the next. As well, the vibrational features of both the ground state and the first excited states of a few of the most populated sites examined are practically the same for the different mixed solvents. The absence of any significant differences in site splitting implies the absence of any dipolar interaction effects on these splittings.The above findings provide a better insight into the interaction between phthalocyanine, intermediate solvent, and basic solvent (n-octane) in the three-component solutions and give a clear guideline for choosing convenient solvents and for using Shpol'skii matrices as a simple effective mechanism for producing quasi-line vibronic spectra of phthalocyanines and other related large molecules insoluble in the alkanes.

scholarly journals Optical absorption spectra of solvated electrons in 1-butylamine–water mixed solvents

1995 ◽  
Vol 73 (12) ◽  
pp. 2126-2130 ◽  
Author(s):  
Yixing Zhao ◽  
Gordon R. Freeman
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Pure Water ◽  
Mixed Solvents ◽  
Binary Solvents ◽  
Optical Absorption Spectra ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Selective Solvation ◽  
Ideal Mixing

The optical absorption spectra of es− in 1-butylamine–water mixed solvents increase smoothly in energy and intensity as the water content is increased, with the exception of a small decrease in intensity on going from 95 to 100 mol% water. At 298 K the value of Gεmax increases from 1.42 × 10−21 m2/16 aJ (8.6 × 103 es−L/100 eV mol cm) in pure 1-butylamine to 8.3 × 10−21 m2/16 aJ (50 × 103 es−L/100 eV mol cm) in pure water, and the value of EAmax increases from 115 zJ (0.72 eV) to 278 zJ (1.74 eV). In the pure amine, if G(es−) = 0.27, then εmax = 5.3 × 10−21 m2/es− (3200 m2/mol). The solvent composition dependences of Gεmax and EAmax indicate little selective solvation of es− by water; this might be due to relatively "ideal" mixing of water and amine in the binary solvents. The temperature coefficient −dEAmax/dT = 0.43 zJ/K in pure 1-butylamine, 0.47 in pure water, and has a minimum of 0.27 in the 50:50 mixture. Keywords: 1-butylamine–water mixed solvents, optical absorption spectra, solvated electron, temperature dependence.

Solvent structure effects on solvated electron reactions with ions in 2-butanol/water mixed solvents

1991 ◽  
Vol 69 (5) ◽  
pp. 884-892 ◽  
Author(s):  
Sedigallage A. Peiris ◽  
Gordon R. Freeman
Keyword(s):  
Rate Constant ◽  
Pure Water ◽  
Mixed Solvents ◽  
Reaction Rates ◽  
Bimolecular Reaction ◽  
Activation Energies ◽  
Solvated Electron ◽  
Polar Species ◽  
Water Solvent ◽  
Alcohol Water

The Smoluchowski–Debye–Stokes–Einstein equation for the rate constant k2 of a bimolecular reaction between charged or polar species[Formula: see text]was used to evaluate effects of bulk solvent properties on reaction rates of solvated electrons with [Formula: see text] and [Formula: see text] in 2-butanol/water mixed solvents. To explain detailed effects it was necessary to consider more specific behavior of the solvent. Rate constants k2, activation energies E2, and pre-exponential factors A2 of these reactions vary with the composition of 2-butanol/water mixtures. The values of E2 were in general similar to activation energies of ionic conductance EΛ0 of the solutions, except for much higher values of E2 of [Formula: see text] in alcohol-rich solvents and of [Formula: see text] in pure water solvent. The solvent apparently participates chemically in the [Formula: see text] reaction, and the [Formula: see text] reaction is multistep. Rate constant and conductance measurements of thallium acetate solutions in 2-butanol containing zero and 10 mol% water were complicated by the formation of ion clusters larger than pairs. Key words: alcohol/water mixed solvents, ions, reaction kinetics, solvated kinetics, solvated electron, solvent effects.

Article

1998 ◽  
Vol 76 (4) ◽  
pp. 407-410
Author(s):  
Yixing Zhao ◽  
Gordon R Freeman
Keyword(s):  
Pure Water ◽  
Mixed Solvents ◽  
Molar Conductivity ◽  
Solvated Electron ◽  
Pure Ethanol ◽  
Electrical Conductances ◽  
Alcohol Water ◽  
Different Temperatures ◽  
Ion Radius ◽  
Pure Methanol

As a foundation for a future measurement of solvated electron mobilities in alcohol-water mixed solvents, the electrical conductances of sodium tetraphenylboride (STPB) in methanol-water, ethanol-water, and 2-propanol-water were measured at different temperatures. The molar conductivity LAMBDA 0 (10-4 S m2 mol-1) of STPB at 298 K is 70 in pure water and 82 in pure methanol; in methanol-water mixed solvents it passes through a minimum, the value being 45 at 70 mol% water. In 2-propanol-water LAMBDA 0 (10-4 S m2 mol-1) at 298 K decreases rapidly from 70 in pure water to 22.6 in 80 mol% water, then gradually to 16.5 in pure 2-propanol. Behavior in ethanol-water is intermediate, with a minimum of 29.5 in 70 mol% water, gradually increasing to 35.5 in pure ethanol. The product of LAMBDA 0 and the solvent viscosity eta has a maximum at about 75 mol% water in methanol, 90 mol% water in ethanol, and 95 mol% water in 2-propanol. The effects are attributed to changes of solvent structure and of solvated ion radius as alcohol is added to water.Key words: alcohol-water mixed solvents, electrical conductivity, large ions, solvent effects, activation energy.

Solvent structure effects on solvated electron reactions in mixed solvents: positive ions in 1-propanol/water and 2-propanol/water

1991 ◽  
Vol 69 (1) ◽  
pp. 157-166 ◽  
Author(s):  
Sedigallage A. Peiris ◽  
Gordon R. Freeman
Keyword(s):  
Pure Water ◽  
Mixed Solvents ◽  
Reaction Rates ◽  
Mutual Diffusion ◽  
Residual Effects ◽  
Solvated Electron ◽  
Bulk Fluid ◽  
Positive Ions ◽  
Water Solvent ◽  
Alcohol Water

In models of the kinetics of chemical reactions in solution the solvent is commonly assumed to be a uniform continuum. An example is the Smoluchowski–Debye–Stokes–Einstein equation for the rate constant k2 of a bimolecular reaction between charged or polar species:[Formula: see text]where κ is the probability that a reactant encounter pair will react, R is the gas constant, T is the temperature, f is a factor that reflects the effect of electrostatic interaction between the reactants on their probability of attaining the closeness of approach rr at which reaction occurs, η is the solvent viscosity, and rd is the effective radius of the reactant entities for mutual diffusion. The equation is useful in evaluating effects of bulk fluid properties on reaction rates. Residual effects are attributed to more specific solvent behaviour.Rate constants k2, activation energies E2, and pre-exponential factors A2 of reactions of solvated electrons [Formula: see text] with [Formula: see text] [Formula: see text] and [Formula: see text] ions vary with the composition of 1-propanol/water and 2-propanol/water mixed solvents. Plots of k2η/fT against solvent composition are nonlinear and change with the solvent pair and with reactant pair. Measured molar conductivities [Formula: see text] [Formula: see text] [Formula: see text] and [Formula: see text] indicate that the values of rd for the mutual diffusion of the cations and anions have a minimum near 90 mol% water, and that the values in pure propanol-1 or −2 (150–190 pm) are larger than those in pure water solvent (26 pm for [Formula: see text] 70 pm for the metal ions). The liquid structure influences both the rate of diffusion and the probability of reaction of a reactant encounter pair. Key words: alcohol/water mixed solvents, positive ions, reaction kinetics, solvated electron, solvent effects.

Sign in / Sign up

Export Citation Format

Share Document