Triplet Excited State Properties Research Articles

Excited Triplet and Reduced Forms of C84

The triplet excited state behavior of C[sub 84] has been probed by the triplet - triplet energy transfer method using pulse radiolytically generated biphenyl triplets in benzene. The triplet excited state has a weak absorption in the UV (difference absorption maxima at 310 and 345 nm) but no significant absorption in the visible. The rate constants for energy transfer from [sup 3]BP* and [sup 3]C[sub 60]* are 4 [times] 10[sup 9] and 4.7 [times] 10[sup 9] M[sup [minus]1] s[sup [minus]1], respectively. Triplet excited state properties of [sup 3]C[sub 84]* are compared with other fullerenes. A photocatalytic method has also been successfully employed to reduce C[sub 84] in a UV-irradiated colloidal TiO[sub 2] suspension. 36 refs., 4 figs., 1 tab.

ChemInform Abstract: Enone Photochemistry. Dynamic Properties of Triplet Excited States of Cyclic Conjugated Enones as Revealed by Transient Absorption Spectroscopy

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Enone photochemistry. Dynamic properties of triplet excited states of cyclic conjugated enones as revealed by transient absorption spectroscopy

Enone photochemistry. Dynamic properties of triplet excited states of cyclic conjugated enones as revealed by transient absorption spectroscopy

Photophysics and photochemistry of phenosafranin dye in aqueous and acetonitrile solutions

The singlet and triplet excited state properties of phenosafranin dye were characterized in aqueous and acetonitrile solutions. The singlet excited state exhibited an absorption maximum at ∼ 430 nm and a lifetime of 930 ps in aqueous medium. The transient absorption spectra of the protonated and unprotonated forms of excited triplet were investigated by the laser flash photolysis technique. The protonated phenosafranin triplet had absorption maxima at 380 nm (ϵ = 11 000 M −1 cm −1), 615 nm (ϵ = 9700 M −1 cm −1) and 665 nm (ϵ = 10 800 M −1) and the unprotonated phenosafranin triplet had absorption maxima at 410 nm (ϵ = 8800 M −1 cm −1), 700 nm (ϵ = 6900 M −1 cm −1) and 790 nm (ϵ = 11 600 M −1 cm −1) in aqueous medium. The p K a of the protonated triplet phenosafranin was found to be 7.25. Diffusion-controlled quenching of the excited phenosafranin triplet by amines led to the reduction of the dye. The absorption spectra of the semireduced phenosafranin, which was characterized in acetonitrile, exhibited absorption maxima at 440 nm (ϵ = 29 000 M −1 cm −1) and 870 nm (ϵ = 19 000 M −1 cm −1).

Anomalous magnetic properties of triplet excited states in crystalline and amorphous arsenic triselenide.

Anomalous magnetic properties of triplet excited states in crystalline and amorphous arsenic triselenide.

Photophysical properties of aminomethylpsoralen in presence and absence of DNA

Some properties of the first triplet and singlet excited states of 4′-aminomethyl-4,5′,8-trimethylpsoralen have been determined by laser flash photolysis and spectrofluorimetry. In water the lowest triplet has an intrinsic lifetime of 100 μs and is quenched by the molecule in its ground state with a rate constant k Q = 10 9 M −1·s −1 and by thymine with a rate constant k q = 2 · 10 8 M −1·s −1. Addition of 0.5 mg/ml of calf thymus DNA causes the disappearance of the aminomethylpsoralen triplet absorption immediately after the laser flash excitation and extinguishes the fluorescence emission of a 6 · 10 −5 M solution of aminomethylpsoralen. These experiments show that the first singlet excited state which is rapidly deactivated in the presence of DNA could be the precursor of the first pyrimidine photoadduct.

Selective excitation and dynamic properties of excited triplet states in 2-benzoylpyridine single crystals

Optical and microwave spectral characteristics of the lowest excited triplet state of 2-benzoylpyridine single crystals at 4.2 K depend on whether excitation is into the singlet (S 1←S 0) or triplet manifolds (T 1←S 0). The observed time resolved modulated phosphorescence has been simulated and non-radiative processes found to be significant in determining this wavelength dependence.

Phosphorescence study of excited triplet state properties of some K vitamins and their analytical usefulness.

Phosphorescence study of excited triplet state properties of some K vitamins and their analytical usefulness.

Photochemistry of pyridine N-oxides. Chemical properties of single and triplet excited states

Sensitization of the pyridine N-oxide triplet state increases the extent of oxygen transfer reactions, whereas quenching with a copper salt in aqueous solution increases the extent of photorearrangement.

Photochemistry of aromatic compounds. Part 1.—Acid-base properties of singlet and triplet excited states of pyrene derivatives and aza-aromatic compounds

Variations of acidity constants between the ground state G and the fluorescent state S1 of 1-, 2-, 4- and 9-azaphenanthrenes, 1-aminopyrene, 1-hydroxypyrene and pyrene-1-carboxylic acid have been measured by application of the Forster cycle. Triplet state pK values of the same derivatives were obtained by the flash photolysis technique. For 1-hydroxypyrene under flash photolysis conditions, only one transient, whose spectrum is not pH dependent could be observed. This transient spectrum has been assigned to the pyrenoxyl radical. There appears to be no relationship between the position of protonation of the various aza-phenanthrenes and the ΔpK between the ground state and the singlet or triplet excited states.