Hydrated Electrons Formed in the Flash Photolysis of Ag° and Tl°

1973 ◽  
Vol 51 (15) ◽  
pp. 2497-2501 ◽  
Author(s):  
Norman Basco ◽  
Sunil K. Vidyarthi ◽  
David C. Walker
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Work Function ◽  
Wavelength Range ◽  
Flash Photolysis ◽  
Transient Species ◽  
Hydrated Electrons ◽  
A Charge ◽  
Silver Metal ◽  
Double Flash

The transient species Ag0, formed in the reduction of Ag+ by hydrated electrons, may be photodissociated to eaq− again by light in the absorption band of Ag0 centered at ~315 nm.[Formula: see text]It suggests that this band is a charge-transfer-to-solvent band. The photon energy threshold for photoionization of Ag0 (3.0 eV) is substantially smaller than the vacuum photoelectric work function of silver metal (4.5 eV). Analogous results were obtained in solutions of Tl+ indicating that Tl0 may also yield eaq− on photolysis at ~300 nm. The experiments utilized a double flash photolysis technique, in which hydrated electrons were produced by u.v. photolysis of SO42− in the first flash, reacted with Ag+ or Tl+ to give the short-lived intermediates Ag0 (lifetime ~60 μs) and T10 (lifetime < 20 μs) which were photolyzed by a second flash containing light in a restricted wavelength range.

A Transient Intermediate in the Bimolecular Reaction of Hydrated Electrons

1972 ◽  
Vol 50 (13) ◽  
pp. 2059-2070 ◽  
Author(s):  
N. Basco ◽  
G. A. Kenney-Wallace ◽  
S. K. Vidyarthi ◽  
D. C. Walker
Keyword(s):  
Absorption Band ◽  
Extinction Coefficient ◽  
Pulse Radiolysis ◽  
Flash Photolysis ◽  
Bimolecular Reaction ◽  
Considerable Extent ◽  
Transient Species ◽  
Hydrated Electrons ◽  
Mean Lifetime ◽  
Transient Intermediate

Further studies are reported which attempt to identify the transient species (X) produced from hydrated electrons which may be photodissociated to re-form [Formula: see text] The method used involves the production of [Formula: see text] by u.v. flash photolysis of aqueous OH−/H2 solutions followed, after any specified delay, by a second and third photoflash of restricted wavelengths. Photoregeneration of [Formula: see text] is effected by light in the spectral range 320 to 400 nm, not at λ > 700 nm as earlier reported (1). The species X is much longer lived than [Formula: see text] having a mean lifetime of ∼5 ms at pH 11, but this is very dependent on the lifetime of [Formula: see text] in the system. Two conditions seem to be necessary in order to detect the presence of X, (i) [Formula: see text] must decay to a considerable extent through the bimolecular dimerisation reaction and (ii) the lifetime of [Formula: see text] with respect to all other reactions must be >ca. 200 μs. Thus it is not expected to be observable in most pulse radiolysis studies. Its extinction coefficient in that part of its absorption band which leads to photodissociation (320–400 nm) is estimated to average >2000 M−1 cm−1, may be as high as 6000 M−1 cm−1 at 347 nm but does not exceed 12 000 M−1 cm−1 at any wavelength. Its identity is discussed and it is concluded that X is probably the hydrated electron dimer, [Formula: see text] or a product formed there from by association with a cation.

Hydrated Electrons Produced by the Flash Photolysis of Co+, Ni+, Zn+, and Cd+ Ions

1974 ◽  
Vol 52 (2) ◽  
pp. 343-347 ◽  
Author(s):  
Norman Basco ◽  
Sunil K. Vidyarthi ◽  
David C. Walker
Keyword(s):  
Charge Transfer ◽  
Flash Photolysis ◽  
Charge Transfer Band ◽  
Absorption Bands ◽  
Electron Pairs ◽  
Monovalent Ions ◽  
Hydrated Electrons ◽  
Dilute Aqueous Solution ◽  
Sulfate Salts ◽  
Double Flash

Hydrated electrons are produced with a quantum yield of about unity when the low valence state ions Co+, Ni+, Zn+, and Cd+ are photolyzed by light within their absorption bands centered at ∼300 nm. The observations seem to offer direct evidence that these absorption bands may be assigned as charge-transfer bands, and specifically as charge-transfer-to-solvent (c.t.t.s.). The ions are probably present as simple aquo complexes, since they were formed initially in very dilute aqueous solution from the divalent sulfate salts; but they may be solvated ion–electron pairs. Cu+ ions do not show a similar strong charge-transfer band at any wavelengths >230 nm and the second maximum in the case of Co+ at 360 nm is not of the c.t.t.s. type.The experiments used a double flash photolysis method whereby the first flash photolyzed SO42− with light at λ < 220 nm to produce hydrated electrons which then reacted with Co2+, Ni2+, Zn2+, or Cd2+ ions present at 10−5 to 10−6 M. The short-lived monovalent ions so formed were photolyzed 10–300 µs later by the second flash of restricted wavelengths.

Triplet energies of fumaronitrile and maleonitrile

1982 ◽  
Vol 60 (3) ◽  
pp. 339-341 ◽  
Author(s):  
Po Cheong Wong
Keyword(s):  
Charge Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Benzene Solution ◽  
Laser Flash ◽  
Transfer Mechanism ◽  
Triplet Energy ◽  
Charge Transfer Mechanism ◽  
A Charge

The triplet energies of fumaronitrile and maleonitrile measured by laser flash photolysis technique using the Herkstroeter–Hammond method are both 59 ± 2 kcal mol−1. Our results show that these olefins are classical triplet energy acceptors for non-electron donating sensitizers. With electron donating sensitizers, quenching through a charge-transfer mechanism also occurs in benzene solution.

Photoconduction in Metal-Free Phthalocyanine Films

1985 ◽  
Vol 38 (7) ◽  
pp. 1061 ◽  
Author(s):  
S Nespurek ◽  
RHG Hart ◽  
JS Bonham ◽  
LE Lyons
Keyword(s):  
Thin Films ◽  
Charge Transfer ◽  
Wavelength Range ◽  
Charge Transfer Complex ◽  
Pyromellitic Dianhydride ◽  
Carrier Generation ◽  
Metal Free ◽  
Type Process ◽  
Additional Process ◽  
A Charge

By using pulsed photoconductivity techniques, transient action spectra have been recorded on vacuum-sublimed a metal-free phthalocyanine thin films in the wavelength range 350-700 nm. The transient photocurrents were determined at fields less than 107 V m-1 by range-limited transport of holes, the μT product of photogenerated holes being c. 2×10-14 m2 V-1. The electron μT product was about 100 times smaller. Carrier generation was a bulk phenomenon. The quantum efficiency was about 1-2% at fields up to 107 V m-1, and it was increased several fold by the presence of a layer of the acceptor pyromellitic dianhydride. Photogeneration in phthalocyanine occurred by an Onsager -type process. When pyromellitic dianhydride was present, an additional process of carrier generation, not of Onsager type, occurred, possibly associated with an exciton reaction with a charge-transfer complex between α metal-free phthalocyanine and pyromellitic dianhydride .

scholarly journals The chemistry of vitamin B12. The coordination of biologically important molecules

1970 ◽  
Vol 120 (2) ◽  
pp. 263-269 ◽  
Author(s):  
H. A. O. Hill ◽  
J. M. Pratt ◽  
R. G. Thorp ◽  
B. Ward ◽  
R. J. P. Williams
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Hydrogen Bonds ◽  
Vitamin B12 ◽  
Extinction Coefficient ◽  
Equilibrium Constants ◽  
Thiol Group ◽  
Intense Absorption Band ◽  
Intense Absorption ◽  
A Charge

The following equilibrium constants (given as logK in units of m−1) were determined for the substitution of co-ordinated H2O in aquocobalamin by glycine (bound through N) 5.8, cysteine (bound through S) 6.0 or 8.3, depending on the value chosen for the pK of the thiol group, and phenolate 2.9. The spectrum of the phenolate cobalamin shows an additional intense absorption band at 468nm with a molar extinction coefficient of 1.1×104, which is assigned to a charge transfer from the phenolate to the cobalt ion. Equilibrium constants have also been determined for the equilibria between adenylcobamide cyanide and CN−, HO− and H+, which show that the adenine is more easily displaced by CN− and HO− than is 5,6-dimethylbenziminazole in vitamin B12, but can be protonated by acid while still remaining co-ordinated to the cobalt. It is shown that in the binding of corrinoids to proteins and polypeptides the formation of hydrogen bonds is far more important than co-ordination by the metal.

A charge transfer theory of the photoelectrochemical effect

1972 ◽  
Vol 25 (10) ◽  
pp. 2061
Author(s):  
DB Matthews
Keyword(s):  
Charge Transfer ◽  
Work Function ◽  
Metal Electrode ◽  
Electronic Work Function ◽  
Metal Solution ◽  
Transfer Theory ◽  
Solution Interface ◽  
Proposed Model ◽  
Electrochemical Effect ◽  
A Charge

A model based on the Gurney theory of charge transfer is used to obtain a theory of the photo-electrochemical effect at the metal electrode-electrolyte interface. The theory leads to a means of measuring the effective electronic work function at the metal-solution interface and to a means of testing the proposed model.

The photochemistry of aqueous solutions of Tl(III) perchlorate

1970 ◽  
Vol 48 (19) ◽  
pp. 2955-2959 ◽  
Author(s):  
C. E. Burchill ◽  
W. H. Wolodarsky
Keyword(s):  
Charge Transfer ◽  
Quantum Yield ◽  
Flash Photolysis ◽  
Primary Process ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Upper Limit ◽  
Aqueous Perchloric Acid ◽  
A Chain ◽  
A Charge

In deaerated aqueous perchloric acid solution Tl(III) is reduced and 2-propanol oxidized to acetone in equivalent yields via a chain reaction initiated by light of 2537 Å. Initiation is attributed to a charge-transfer-to-metal excitation followed by dissociation[Formula: see text]The formation of Tl(II) in the primary process is demonstrated by flash photolysis. An upper limit of 0.36 ± 0.07 is estimated for the primary quantum yield.

Determination of Epsilon Aminocaproic Acid Based on Charge Transfer Complexation with p-Nitrophenlol by Spectrophotometry

2020 ◽  
Vol 16 ◽  
Author(s):  
Sheng-Yun Li ◽  
Fang Tian
Keyword(s):  
Charge Transfer ◽  
Aminocaproic Acid ◽  
Concentration Limit ◽  
Official Method ◽  
Good Precision ◽  
Pharmaceutical Dosage Forms ◽  
Relative Standard ◽  
A Charge ◽  
Epsilon Aminocaproic Acid

: A spectrophotometry was investigated for the determination of epsilon aminocaproic acid (EACA) with p-nitrophenol (PNP). The method was based on a charge transfer (CT) complexation of this drug as n-electron donor with π-acceptor PNP. Experiment indicated that the CT complexation was carried out at room temperature for 10 minutes in dimethyl sulfoxide solvent. The spectrum obtained for EACA/PNP system showed the maximum absorption band at wavelength of 425 nm. The stoichiometry of the CT complex was found to be 1:1 ratio by Job’s method between the donor and the acceptor. Different variables affecting the complexation were carefully studied and optimized. At the optimum reaction conditions, Beer’s law was obeyed in a concentration limit of 1～6 µg mL-1. The relative standard deviation was less than 2.9%. The apparent molar absoptivity was determined to be 1.86×104 L mol-1cm-1 at 425 nm. The CT complexation was also confirmed by both FTIR and 1H NMR measurements. The thermodynamic properties and reaction mechanism of the CT complexation have been discussed. The developed method could be applied successfully for the determination of the studied compound in its pharmaceutical dosage forms with a good precision and accuracy compared to official method as revealed by t- and F-tests.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

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