Université de Fribourg

Vibronic spectra of the p-benzoquinone radical anion and cation: a matrix isolation and computational study

Piech, Krzysztof ; Bally, Thomas ; Ichino, Takatoshi ; Stanton, John

In: Physical Chemistry Chemical Physics, 2013, vol. 16, no. 5, p. 2011–2019

The electronic and vibrational absorption spectra of the radical anion and cation of p-benzoquinone (PBQ) in an Ar matrix between 500 and 40 000 cm⁻¹ are presented and discussed in detail. Of particular interest is the radical cation, which shows very unusual spectroscopic features that can be understood in terms of vibronic coupling between the ground and a very low-lying excited...

Université de Fribourg

Carbocations generated under stable conditions by ionization of matrix-Isolated radicals: the allyl and benzyl cations

Mišić, Vladimir ; Piech, Krzysztof ; Bally, Thomas

In: Journal of the American Chemical Society, 2013, vol. 135, no. 23, p. 8625–8631

Carbocations are crucial intermediates in many chemical reactions; hence, considerable effort has gone into investigating their structures and properties, for example, in superacids, in salts, or in the gas phase. However, studies of the vibrational structure of carbocations are not abundant, because their infrared spectra are difficult to obtain in superacids or salts (where furthermore the...

Université de Fribourg

The bisketene radical cation and its formation by oxidative ring-Opening of cyclobutenedione

Piech, Krzysztof ; Bally, Thomas ; Allen, Annette D. ; Tidwell, Thomas T.

In: The Journal of Organic Chemistry, 2013, vol. 78, no. 7, p. 2908–2913

Parent cyclobutenedione 1 was photolyzed and ionized in an Ar matrix at 10K. The bisketene 2 that results in both cases (in the form of its radical cation after ionization) was characterized by its IR spectrum and by high-level quantum chemical calculations. Experiment and theory show that the neutral bisketene has only a single conformation where the two ketene moieties are nearly perpendicular,...

Université de Fribourg

Mechanistic aspects of the oxidative and reductive fragmentation of n-nitrosoamines: a new method for generating nitrenium cations, amide anions, and aminyl radicals

Piech, Krzysztof ; Bally, Thomas ; Sikora, Adam ; Marcinek, Andrzej

In: Journal of the American Chemical Society, 2007, vol. 129, no. 11, p. 3211 -3217

A new method for investigating the mechanisms of nitric oxide release from NO donors under oxidative and reductive conditions is presented. Based on the fragmentation of N-nitrosoamines, it allows generation and spectroscopic characterization of nitrenium cations, amide anions, and aminyl radicals. X-irradiation of N-nitroso-N,N-diphenylamine 1 in Ar matrices at...

Université de Fribourg

Oxidative rearrangements of tricyclic vinylcyclobutane derivatives

Grota, Juliane ; Mattay, Jochen ; Piech, Krzysztof ; Bally, Thomas

In: Chemistry - A European Journal, 2006, vol. 12(17), p. 4559-4567

Three tricyclic vinylcyclobutanes (3-methylenetricyclo[,6]decanes 1-3) have been subjected to ionization by photoinduced electron transfer in solution and by X-irradiation in Ar matrices. All three compounds undergo oxidative cycloreversion; the cleavage of the four-membered ring, however, occurs in a different direction depending on the presence of a methyl group...