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Université de Fribourg

Amide neighbouring-group effects in peptides: phenylalanine as relay amino acid in long-distance electron transfer

Nathanael, Joses G. ; Gamon, Luke F. ; Cordes, Meike ; Rablen, Paul R. ; Bally, Thomas ; Fromm, Katharina M. ; Giese, Bernd ; Wille, Uta

In: ChemBioChem, 2018, vol. 19, no. 9, p. 922–926

In nature, proteins serve as media for long‐distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single‐step superexchange or through a multi‐step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long‐distance electron...

Université de Fribourg

Variations in rotational barriers of allyl and benzyl cations, anions, and radicals

Li, Zhe ; Bally, Thomas ; Houk, Kendall N. ; Borden, and Weston Thatcher

In: The Journal of Organic Chemistry, 2016, vol. 81, no. 20, p. 9576–9584

High accuracy quantum chemical calculations show that the barriers to rotation of a CH2 group in the allyl cation, radical, and anion are 33, 14, and 21 kcal/mol, respectively. The benzyl cation, radical, and anion have barriers of 45, 11, and 24 kcal/mol, respectively. These barrier heights are related to the magnitude of the delocalization stabilization of each fully conjugated system. This...

Université de Fribourg

Unusual Rearrangements of Radical Cations: The Role of Vibronic Coupling

Bally, Thomas

In: CHIMIA International Journal for Chemistry, 2016, vol. 70, no. 3, p. 164–171

Radicalcations often undergo very unexpected rearrangements. Three examples of such rearrangements are given, and it is shown how vibronic coupling between the ground and low-lying excited states may cause certain bonds that are quite solid in the neutral molecules to become so weak that they break spontaneously, even though the bond order does not change (or changes very little) on...

Université de Fribourg

Proline as a charge stabilizing amino acid in peptide radical cations

Monney, Nicolas P.-A. ; Bally, Thomas ; Giese, Bernd

In: Journal of Physical Organic Chemistry, 2015, vol. 28, no. 5, p. 347–353

Long distance electron transfer in proteins requires relay stations that can be transitorily oxidized or reduced. Although individual prolines cannot assume this function, because of their high ionization energy, it has been shown that polyprolines have the ability to transfer charges. In order to determine the role of the proline in the hole distribution and transport within a PheProPhe...

Université de Fribourg

Electromers of the benzene dimer radical cation

Błoch-Mechkour, Anna ; Bally, Thomas

In: Physical Chemistry Chemical Physics, 2015, vol. 17, no. 16, p. 10624–10629

The well-studied benzene dimer radical cation, which is prototypical for this class of species, has been reinvestigated computationally. Thereby it turned out that both the σ-hemibonded and the half-shifted sandwich structures of the benzene dimer cation, which had been independently proposed, represent stationary points on the B2PLYP-D potential energy surfaces. However, these structures belong...

Université de Fribourg

One-pot synthesis and AFM imaging of a triangular aramide macrocycle

Storz, Christof ; Badoux, Michael ; Hauke, Christopher M. ; Šolomek, Tomáš ; Kühnle, Angelika ; Bally, Thomas ; Kilbinger, Andreas F. M.

In: Journal of the American Chemical Society, 2014, vol. 136, no. 37, p. 12832–12835

Macrocyclizations in exceptionally good yields were observed during the self-condensation of N-benzylated phenyl p-aminobenzoates in the presence of LiHMDS to yield three-membered cyclic aramides that adopt a triangular shape. An ortho-alkyloxy side chain on the N-benzyl protecting group is necessary for the macrocyclization to occur. Linear polymers are formed exclusively in the absence of this...

Université de Fribourg

The Primary steps in excited-state hydrogen transfer: the phototautomerization of o-nitrobenzyl derivatives

Šolomek, Tomáš ; Bochet, Christian G. ; Bally, Thomas

In: Chemistry – A European Journal, 2014, vol. 20, no. 26, p. 8062–8067

The quantum yield for the release of leaving groups from o-nitrobenzyl “caged” compounds varies greatly with the nature of these leaving groups, for reasons that have never been well understood. We found that the barriers for the primary hydrogen-atom transfer step and the efficient nonradiative processes on the excited singlet and triplet surfaces determine the quantum yields. The...

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

Spectroscopic evidence for a new type of bonding between a thioether radical cation and a phenyl group

Monney, Nicolas P.-A. ; Bally, Thomas ; Bhagavathy, Ganga S. ; Glass, Richard S.

In: Organic Letters, 2013, vol. 15, no. 19, p. 4932–4935

The oxidation potential of thioethers constrained to be near aromatic rings is lowered, due to an antibonding interaction between the p-type sulfur lone pair with the neighboring phenyl π-system which on removal of an electron becomes a new kind of 3-electron S∴π bonding that reveals itself in the photoelectron spectrum and by an electronic transition involving the orbitals participating in...

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...