Photolysis of pyrene and chloropyrene in the presence of triethylamine in acetonitrile: dehalogenation assisted by potassium cyanide

Abstract

Kinetics and transient absorption spectra of pyrene-and 1 -chloropyrene-triethylamine (TEA) systems, in the presence and absence of cyanide ions, have been studied b y a nanosecond timeresolved laser flash photolysis method in dry acetonitrile at room temperature. Schemes for c h loropyrene-triet hylami ne-and c h loropyrene-triet hylami ne-CNsystems have been developed and individual rate constants determined either b y direct measurements or by use of computer analysis of the experimental decay curves. The reaction results in the dehalogenation of chloropyrene t o yield pyrene as the reaction product, but high quantum yields (0.2-0.4) are obtained only in the presence of cyanide ions. The hydrogen atoms which replace the chlorines originate from the solvent. This was determined b y deuterium labelling. The reaction proceeds via an exciplex t o radical ions, which recombine to form ion pairs. Cyanide ions attract chlorohydropyrene radicals, which are mainly formed in the reaction between chloropyrene anion radicals and the solvent. The cyanohydropyrenyl radicals formed are in equilibrium with the relatively stable cyanopyrene anion radicals and, b y cleavage of the cyano radicals, yield the reaction product.Paper 1/03584C

Photoreduction of IrCl62? complex in alcohol solutions and its reaction with hydroxyalkyl radicals

“…For stationary photolysis of an eximer XeCl 2Ϫ IrCl 6 laser was used. (308 nm) Laser-flash photolysis setup [18] consisted of an eximer laser for excitation (wavelength pulse 308 nm, duration ), a xenon arch lamp with a mono-20 ns chromator as a source of probing light and a monochromator with a photomultiplier in the measuring channel. The photomultiplier signal was supplied to a digital Tektronix 7912AD oscilloscope connected with an IBM type computer.…”

Photochemistry of the IrCl6 2− complex in aqueous solutions in the presence of the bromide anions

“…The laser flash photolysis instrument 16 consists of an excimer laser for excitation (wavelength 308 nm, pulse duration 20 ns), a xenon arc lamp with a monochromator, and a photomultiplier in the counting channel. The signal from the photomultiplier was recorded on a Tektronix 7912AD digital oscillograph con nected with an IBM computer.…”

Photochromic processes in di(mercaptoquinolinato)Ni(II) complex and perfluordiphenyl disulfide solutions

“…At long measurement times the photochemical effect of the probing light on the studied solutions was reduced by using a halogen incandescent lamp (less intensive than the xenon one) whose radiation was passed through the narrow-band interference filters. Some experiments were performed on a slightly different laser flash photolysis setup 18 with perpendicular excitation and probe light beams. The signal from the photomultiplier was recorded by Tektronix 7912AD oscilloscope connected to a computer.…”