Laser photoionization and light-initiated redox reactions of tetramethylbenzidine in organic solvents and aqueous micellar solution

Alkaitis, S. A.; Gräetzel, Michael

doi:10.1021/ja00428a027

Cited by 115 publications

(42 citation statements)

References 4 publications

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“…Aromatic hydrocarbons such as pyrene, perylene, and tetracene photoionize [18] by a biphotonic process, whereas aromatic amines with low oxidation potentials such as tetramethylbenzidine [37] and phenothiazine [38] undergo monophotonic ionization. Photoionization of phenothiazine has been studied extensively in homogeneous and micellar solutions and it has been reported that the photoionization process depends on the excitation wavelength.…”

Section: Monophotonic and Biphotonic Ionizationmentioning

confidence: 99%

Excited‐State Behavior and Photoionization of 1,8‐Acridinedione Dyes in Micelles—Comparison with NADH Oxidation

Selvaraju

Ramamurthy

2004

Chemistry A European J

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The photophysics and photochemistry of 1,8-acridinedione dyes, which are analogues of reduced nicotinamide adenine dinucleotide (NADH), are studied in anionic and cationic micelles. Acridinedione dyes (ADDs) are solubilized in micelles at the micelle-water interface and are in equilibrium between the aqueous and micellar phase. The binding of the ADDs with micelles is attributed to hydrophobic interactions and the binding constants are determined with steady-state and time-resolved techniques. Nanosecond laser flash photolysis studies are carried out in aqueous, anionic, and cationic micellar solutions. The ADD undergoes photoionization in the excited state to give a solvated electron. The solvated electron reacts with the ADD to give an anion radical. In anionic micelles, the yield of the solvated electron increases because of the efficient separation of the cation radical and the electron. Cation radicals derived from the photooxidation of ADDs are involved in keto-enol tautomerization. Under acidic conditions, an enol radical cation of the acridinedione dye is formed from the keto form of the cation radical by intramolecular hydrogen atom transfer. In cationic micelles, due to electrostatic attraction, the electron cannot escape from the micelle and recombination of the cation radical and the electron results in the formation of a triplet state. For the first time, a solvated electron is observed in the laser flash photolysis of ADDs in anionic micelles. The photoionization of ADDs depends on the excitation wavelength and is biphotonic at 355 nm and monophotonic at 248 nm. From the results with this NADH model compound, the sequential electron-proton-electron transfer oxidation of NADH is confirmed and the nature of the intermediates involved in the oxidation is unraveled; these intermediates are found to depend on the pH value of the medium.

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Section: Monophotonic and Biphotonic Ionizationmentioning

confidence: 99%

Excited‐State Behavior and Photoionization of 1,8‐Acridinedione Dyes in Micelles—Comparison with NADH Oxidation

Selvaraju

Ramamurthy

2004

Chemistry A European J

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“…It has recently been found that molecules of low gas phase ionization energy (-6.5 eV) such as phenothiazine (33) and tetramethylbenzidine (34) can be ionized by 3.56 eV quanta (frequency doubled ruby laser) if they are irradiated in the lipoidic interior of anionic micelles in aqueous solution. Immediately after the 10 ns laser flash, the spectrum of the hydrated electror: and that of the cation of the solubilized molecule could be seen.…”

Section: Heterogeneous Electron Transfermentioning

confidence: 99%

Electron reactivity as a function of phase

Henglein¹

1977

Can. J. Chem.

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A. HENGLEIN. Can. J. Chem. 55.21 12 (1977). Reactions of free electrons in the gas phase, of quasi-free electrons and solvated electrons in dielectric liquids, of hydrated electrons in water, and of electrons originating from an electrode in contact with a solution are among the great variety of electronic processes in chemistry. It 1s the purpose of this paper to describe a few phase effects. Reactions of electrons in dielectric liquids will be discussed with respect to the corresponding processes in the gas phase. Furthermore, certain aspects in the transfer of an electron from a hydrocarbon phase into the aqueous phase will be dealt with. The processes will be described in terms of electronic redox level distributions of the acceptor redox systems.

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“…The extinction coefficient of Hyp •-at 735 nm was estimated by comparison of the absorption at 735 nm to that of the TMB •+ radical at 470 nm ( ) 4.1 × 10 4 M -1 cm -1 ) 47 and the absorption of TMPD •+ at 570 and 620 nm ( ) 1.3 × 10 4 M -1 cm -1 ) 48 as shown in Figure 3a,b. In both cases, max (Hyp •-) ) 2.0 × 10 4 M -1 cm -1 was obtained and also when using bleaching of Hyp ground state at 590 nm as a standard.…”

Section: Resultsmentioning

confidence: 99%

Quenching of Excited Triplet State Hypericin with Energy Acceptors and Donors and Acceptors of Electrons

and¹,

Jenks²,

and³

et al. 1999

J. Phys. Chem. B

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The quenching of the triplet state of hypericin by acceptors of electronic energy and donors and acceptors of electrons was studied by nanosecond laser photolysis. The energy of triplet hypericin is E T ) 13 350 cm -1 , and for acceptors with E T < 13 300 cm -1 the observed energy transfer rate constant declines with increasing exothermicity. Quenching of triplet hypericin by amines in acetonitrile and electron acceptors in DMSO occurs via electron transfer. Spectroscopic and kinetic properties and the quantum yield of hypericin radical ion formation were established. The rate constant profiles for electron transfer (in both directions) are consistent with an excited-state reaction occurring before electron transfer. The rate constant of the interaction of reduced hypericin with O 2 was estimated to be 3.8 × 10 8 M -1 s -1 in acetonitrile.

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Laser photoionization and light-initiated redox reactions of tetramethylbenzidine in organic solvents and aqueous micellar solution

Cited by 115 publications

References 4 publications

Excited‐State Behavior and Photoionization of 1,8‐Acridinedione Dyes in Micelles—Comparison with NADH Oxidation

Excited‐State Behavior and Photoionization of 1,8‐Acridinedione Dyes in Micelles—Comparison with NADH Oxidation

Electron reactivity as a function of phase

Quenching of Excited Triplet State Hypericin with Energy Acceptors and Donors and Acceptors of Electrons

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