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Université de Fribourg

Regioselective oxidative ring opening of cyclopropyl silyl ethers: a quantum chemical study

Rinderhagen, Heiko ; Mattay, Jochen ; Nussbaum, Rafael ; Bally, Thomas

In: Chemistry, a European Journal, 2010, vol. 16, no. 24, p. 7121–7124

In contrast to the structurally and configurationally stable alkyl- or aryl-substituted cyclopropyl radical cations, cyclopropyl silyl ethers undergo spontaneous ring opening upon oxidation whereby the endocyclic C-C(O-TMS) bond is cleaved with remarkable selectivity. DFT calculations on 1-trimethylsilyloxybicyclo[4.1.0]heptane show that this selectivity arises from the topology of the potential...

Université de Fribourg

Isomerism: the same but different

Bally, Thomas

In: Nature Chemistry, 2010, vol. 2, no. 3, p. 165-166

Electromerism is an unfamiliar concept to many chemists and refers to molecules that are not conventional isomers but instead differ in how the electrons are distributed across their structure. A novel example of such electromers has now been demonstrated.

Université de Fribourg

Calculating accurate proton chemical shifts of organic molecules with density functional methods and modest basis sets

Jain, Rupal ; Bally, Thomas ; Rablen, Paul R.

In: The Journal of Organic Chemistry, 2009, vol. 74, no. 11, p. 4017–4023

The purpose of this paper is to convince practitioners of ¹H NMR spectroscopy to consider simple quantum chemical calculations as a viable option to aid them in the assignment of their spectra. To this end, it is demonstrated, on a test set of 80 conformationally stable molecules of various kinds carrying different functional groups, that, in contrast to what is claimed in the literature, large...

Université de Fribourg

Photochemical study on the reactivity of tetrasulfur tetranitride, S₄N₄

Pritchina, Elena A. ; Gritsan, Nina P. ; Zibarev, Andrey V. ; Bally, Thomas

In: Inorganic Chemistry, 2009, vol. 48, no. 9, p. 4075–4082

To elucidate the multifaceted but poorly understood chemistry of the pivotal polysulfur−nitrogen heterocycle, tetrasulfur tetranitride (S₄N₄, 1), its photochemistry was studied in Ar matrices. Thereby two primary intermediates and a secondary one (2−4) were detected, and their UV−vis and IR spectra were identified through specific interconversions of...

Université de Fribourg

Electronic structure and absorption spectra of biferrocenyl and bisfulvalenide diiron radical cations: detection and assignment of new low-energy transitions

Warratz, Ralf ; Aboulfadl, Hanane ; Bally, Thomas ; Tuczek, Felix

In: Chemistry - A European Journal, 2009, vol. 15, no. 7, p. 1604 - 1617

Low-energy electronic transitions have been detected spectroscopically in the FeII-FeIII mixed-valent biferrocenyl radical cation, but are absent in the spectra of the neutral analogue. They have been assigned by time-dependent DFT calculations (squares in figure). Analogous investigations were performed for the bisfulvalenide FeII-FeIII radical cation....

Université de Fribourg

Ultrafast Spectroscopic and Matrix Isolation Studies of p-Biphenylyl, o-Biphenylyl, and 1-Naphthylnitrenium Cations

Wang, Jin ; Burdzinski, Gotard ; Zhu, Zhendong ; Platz, Matthew S. ; Carra, Claudio ; Bally, Thomas

In: Journal of the American Chemical Society, 2007, vol. 129, no. 26, p. 8380-8388

p-Biphenylyl, o-biphenylyl, and 1-naphthyl azides were deposited in argon at low temperature in the presence and absence of HCl. In the absence of HCl, the known electronic and vibrational spectra of the corresponding triplet nitrenes, azirines, and didehydroazepines were observed, whereas in the presence of HCl, photolysis of these azides produces new electronic spectra assigned to...

Université de Fribourg

Photochemistry of reactive intermediates

Bally, Thomas

In: Chimia, 2007, vol. 61, no. 10, p. 645-649

This paper illustrates the research on the photochemistry of reactive intermediates that was (and still is) carried out in the author's research group on three typical examples: the photochemistry of arylcarbenes, arylnitrenes, and organic radical cations.

Université de Fribourg

Matrix isolation and computational study of the photochemistry of 1,3,2,4-Benzodithiadiazine

Gritsan, Nina P. ; Pritchina, Elena A. ; Bally, Thomas ; Makarov, Alexander Yu. ; Zibarev, Andrey V.

In: The Journal of Physical Chemistry A, 2007, vol. 111, no. 5, p. 817 -824

Photolysis of 1,3,2,4-benzodithiadiazine (1) at ambient temperature yields stable 1,2,3-benzodithiazolyl radicals. In order to reveal the mechanism of this unusual transformation, the photochemistry of 1 was studied in argon matrices using IR and UV-vis spectroscopy. A series of intermediates, including four- and five-membered heterocyclic and o-quinoid acyclic species, were characterized...

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...