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...
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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...
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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...
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In: The Journal of Physical Chemistry B, 2015, vol. 119, no. 22, p. 6584–6590
Electron transfer over long distances in proteins by a hopping process requires transient relay stations that can harbor charge and spin for a short time span. Certain easily oxidizable or reducible side chains may assume that role, but it has been shown that charge transport in peptides can also take place in the absence of such groups which implies that the peptide backbone provides for hopping...
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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...
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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...
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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...
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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...
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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...
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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...
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