@phdthesis{Arnold2001,
  author    = {Arnold, Markus A.},
  title     = {Oxidative DNA-Sch{\"a}digung durch elektronisch angeregte Carbonylverbindungen und daraus gebildete Radikalspezies},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-1182038},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2001},
  abstract  = {Mittels Laserblitz-Photolyse wurden die Triplettlebenszeiten sowie die L{\"o}schraten der Triplettzust{\"a}nde verschiedener Acetophenonderivate durch dG, 8-oxodG, DNA, molekularen Sauerstoff und die Ketone selbst bestimmt. F{\"u}r AP-OAc, AP und BP wurden Triplettlebensdauern von 7-9 µs gemessen, w{\"a}hrend die Triplettzust{\"a}nde von AP-OH und AP-OtBu aufgrund alpha Spaltung deutlich kurzlebiger waren (ca. 1 µs); die alpha Spaltung konnte EPR-spektroskopisch durch Spinabfangexperimente mit DMPO und TEMPO belegt werden. Im Fall von AP-OMe wurde weder dessen Triplettzustand noch die Bildung von Radikalen detektiert, was auf einer schnell ablaufenden Norrish-Typ-II-Spaltung beruht. Aufgrund dieses photochemischen Verhaltens wurden die Ketone (mit Ausnahme von AP-OMe) in zwei Gruppen klassifiziert, n{\"a}mlich die „Gruppe A"-Ketone (keine Radikalbildung) und die „Gruppe B"-Ketone (Radikalbildner). W{\"a}hrend die „Gruppe A"-Ketone gegen{\"u}ber niedrigen Konzentrationen von DNA (62.5 µM) inaktiv waren, verursachten die bei der Bestrahlung der „Gruppe B"-Ketone generierten Peroxylradikale, neben wenigen direkt induzierten Strangbr{\"u}chen, haupts{\"a}chlich die Guaninoxidationsprodukte 8-oxoGua und guanidinfreisetzende Produkte (GRP). Erst wenn die DNA-Konzentration zehnfach erh{\"o}ht wird (625 µM), tritt bei der Photolyse der „Gruppe A"-Ketone auch DNA-Oxidation durch einen Elektronentransfer von der Guaninbase auf das angeregte Keton ein. Ein analoger Konzentrationseffekt wurde auch in der dG-Oxidation beobachtet, bei niedrigen Substratkonzentrationen sind nur die radikalbildenden „Gruppe B"-Ketone aktiv. Die Tatsache, dass in der dG-Oxidation durch die „Gruppe A"-Ketone kein 8-oxodG detektiert wurde, wurde auf dessen effiziente Oxidation durch dG•+-Radikalkationen zur{\"u}ckgef{\"u}hrt. Die „Gruppe B"-Ketone sind in Abwesenheit von O2 gegen{\"u}ber dG und DNA oxidativ inaktiv, da die in der alpha Spaltung generierten kohlenstoffzentrierten Radikale keine Peroxylradikale bilden k{\"o}nnen. Die „Gruppe A"-Ketone sind gegen{\"u}ber DNA in Abwesenheit wie auch in Anwesenheit von Sauerstoff genauso reaktiv, da der Elektronentransfer von DNA zum Keton unabh{\"a}ngig von Sauerstoff ist. Um mechanistische Einblicke in die oxidative DNA-Sch{\"a}digung zu erlangen, wurden photochemische Modellstudien mit dem Nukleosid dG sowie 8-oxodG durchgef{\"u}hrt, wobei zus{\"a}tzlich Spiroiminodihydantoin gebildet wird. Bis vor kurzem wurde die Struktur dieses Oxidationsproduktes als 4-HO-8-oxodG angenommen, dass zuerst in der dG Oxidation mit Singulettsauerstoff (1O2) beobachtet wurde. Weder Spiroiminodihydantoin noch 4 HO-8-oxodG sind als authentische Verbindungen bekannt, so dass eine zweifelsfreie Strukturaufkl{\"a}rung die Bestimmung der Konnektivit{\"a}t der markierten Positionen erforderte. Diese Zuordnung erfolgte mittels eines SELINQUATE-NMR Spektrums, mit dem schl{\"u}ssig die 4 HO-8-oxodG-Struktur ausgeschlossen wurde. Wie alle „Gruppe B"-Ketone sind auch alle „Gruppe A"-Ketone in Abwesenheit von O2 mit Ausnahme von AP-OAc gegen{\"u}ber dG inert. Dies ist ein Beleg daf{\"u}r, dass der Elektronentransferschritt von dG zum Keton in Abwesenheit von Sauerstoff (im Gegensatz zur DNA-Oxidation) reversibel ist und daher keine Oxidation m{\"o}glich ist, wenn die Ketylradikale nicht durch O2 abgefangen werden. Das aus AP-OAc gebildete Ketylradikal besitzt als einziges einen effektiven unimolekularen Deaktivierungsweg, n{\"a}mlich die Acetation-abspaltung, so dass die Reversibilit{\"a}t nicht mehr m{\"o}glich ist.},
  subject      = {DNS-Sch{\"a}digung},
  language  = {de}
}
@article{HattoriMichailSchmiedeletal.2019,
  author    = {Hattori, Yohei and Michail, Evripidis and Schmiedel, Alexander and Moos, Michael and Holzapfel, Marco and Krummenacher, Ivo and Braunschweig, Holger and M{\"u}ller, Ulrich and Pflaum, Jens and Lambert, Christoph},
  title     = {Luminescent Mono-, Di-, and Tri-radicals: Bridging Polychlorinated Triarylmethyl Radicals by Triarylamines and Triarylboranes},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {68},
  doi       = {10.1002/chem.201903007},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208162},
  pages     = {15463-15471},
  year      = {2019},
  abstract  = {Up to three polychlorinated pyridyldiphenylmethyl radicals bridged by a triphenylamine carrying electron withdrawing (CN), neutral (Me), or donating (OMe) groups were synthesized and analogous radicals bridged by tris(2,6-dimethylphenyl)borane were prepared for comparison. All compounds were as stable as common closed-shell organic compounds and showed significant fluorescence upon excitation. Electronic, magnetic, absorption, and emission properties were examined in detail, and experimental results were interpreted using DFT calculations. Oxidation potentials, absorption and emission energies could be tuned depending on the electron density of the bridges. The triphenylamine bridges mediated intramolecular weak antiferromagnetic interactions between the radical spins, and the energy difference between the high spin and low spin states was determined by temperature dependent ESR spectroscopy and DFT calculations. The fluorescent properties of all radicals were examined in detail and revealed no difference for high and low spin states which facilitates application of these dyes in two-photon absorption spectroscopy and OLED devices.},
  language  = {en}
}
@article{KrebsHaehnelKrummenacheretal.2021,
  author    = {Krebs, Johannes and Haehnel, Martin and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Finze, Maik and Ji, Lei and Marder, Todd B.},
  title     = {Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {31},
  doi       = {10.1002/chem.202100938},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256841},
  pages     = {8159-8167},
  year      = {2021},
  abstract  = {Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.-}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.-}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.},
  language  = {en}
}
@article{CzernetzkiArrowsmithFantuzzietal.2021,
  author    = {Czernetzki, Corinna and Arrowsmith, Merle and Fantuzzi, Felipe and G{\"a}rtner, Annalena and Tr{\"o}ster, Tobias and Krummenacher, Ivo and Schorr, Fabian and Braunschweig, Holger},
  title     = {A neutral beryllium(I) radical},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {38},
  doi       = {10.1002/anie.202108405},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256529},
  pages     = {20776-20780},
  year      = {2021},
  abstract  = {The reduction of a cyclic alkyl(amino)carbene (CAAC)-stabilized organoberyllium chloride yields the first neutral beryllium radical, which was characterized by EPR, IR, UV/Vis spectroscopy and X-ray crystallography. DFT calculations show significant spin density at beryllium and confirm donor-acceptor bonding between an alkylberyllium radical fragment and a neutral CAAC ligand.},
  language  = {en}
}
@article{HuangHuKrummenacheretal.2022,
  author    = {Huang, Mingming and Hu, Jiefeng and Krummenacher, Ivo and Friedrich, Alexandra and Braunschweig, Holger and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.},
  title     = {Base-Mediated Radical Borylation of Alkyl Sulfones},
  series = {Chemistry—A European Journal},
  volume    = {28},
  journal   = {Chemistry—A European Journal},
  number    = {3},
  doi       = {10.1002/chem.202103866},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257281},
  pages     = {e202103866},
  year      = {2022},
  abstract  = {A practical and direct method was developed for the production of versatile alkyl boronate esters via transition metal-free borylation of primary and secondary alkyl sulfones. The key to the success of the strategy is the use of bis(neopentyl glycolato) diboron (B\(_{2}\)neop\(_{2}\)), with a stoichiometric amount of base as a promoter. The practicality and industrial potential of this protocol are highlighted by its wide functional group tolerance, the late-stage modification of complex compounds, no need for further transesterification, and operational simplicity. Radical clock, radical trap experiments, and EPR studies were conducted which show that the borylation process involves radical intermediates.},
  language  = {en}
}
@phdthesis{Krebs2023,
  author    = {Krebs, Johannes Heinrich},
  title     = {Investigation of Dicarba-closo-dodecaborane as a Substituent on Three-coordinate Boron and as an Acceptor in a Pyrene-Donor-Acceptor System},
  doi       = {10.25972/OPUS-28675},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286758},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {1. Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane, a new bis(o-carboranyl)-(R)-borane 1 was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr2. Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1•- was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1•-, their calculated geometries, and the S1 excited state of 1. 2. The choice of backbone linker for ortho-bis-(9-borafluorene)s has a great influence on the LUMO located at the boron centers and therefore the reactivity of the respective compounds. Herein, we report the room temperature rearrangement of 1,2-bis-(9-borafluorenyl-)-ortho-carborane, C2B10H10-1,2-[B(C12H8)]2 ([2a]) featuring o-carborane as the inorganic three-dimensional backbone and the synthesis of 1,2-bis-(9-borafluorenyl-)benzene, C6H4-1,2-[B(C12H8)]2 (2b) its phenylene analog. DFT calculations on the transition state for the rearrangement support an intramolecular C-H bond activation process via an SEAr-like mechanism in [2a], and predicted that the same rearrangement would take place in 2b, but at elevated temperatures, which indeed proved to be the case. 3. We synthesized 4 a julolidine-like pyrenyl-o-carborane, with pyrene substituted at the 2,7-positions on the HOMO/LUMO nodal plane, continuing our research. Using solid state molecular structures, photophysical data, cyclic voltammetry, DFT and TD-DFT calculations we compare o-carborane and the B(mes)2 (mes = 2,4,6-Me3C6H2) as acceptor groups and confirm the julolidine-like donor strength.},
  subject      = {closo-Borane},
  language  = {en}
}