Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-31889 Wissenschaftlicher Artikel Schleier, Domenik; Gerlach, Marius; Pratim Mukhopadhyay, Deb; Karaev, Emil; Schaffner, Dorothee; Hemberger, Patrick; Fischer, Ingo Ammonia Borane, NH\(_{3}\)BH\(_{3}\): A Threshold Photoelectron-Photoion Coincidence Study of a Potential Hydrogen-Storage Material We have investigated the photoionization of ammonia borane (AB) and determined adiabatic ionization energy to be 9.26±0.03 eV for the X\(^{+}\) \(^{2}\)E←X \(^{1}\)A\(_{1}\) transition. Although the threshold photoelectron spectrum appears at first glance to be similar to the one of the isosteric ethane, the electronic situation differs markedly, due to different orbital energies. In addition, an appearance energy AE\(_{0K}\)-(NH\(_{3}\)BH\(_{3}\), NH\(_{3}\)BH\(_{2}\)\(^{+}\))= 10.00±0.03 eV has been determined, corresponding to the loss of a hydrogen atom at the BH\(_{3}\)-site. From the data, a 0 K bond dissociation energy for the B−H bond in the cation of 71.5±3 kJ mol\(^{-1}\) was derived, whereas the one in the neutral compound has been estimated to be 419±10 kJ mol\(^{-1}\). 2022 Chemistry-A European Journal 28 42 urn:nbn:de:bvb:20-opus-318895 10.1002/chem.202201378 Institut für Physikalische und Theoretische Chemie OPUS4-31233 Wissenschaftlicher Artikel Preitschopf, Tobias; Sturm, Floriane; Stroganova, Iuliia; Lemmens, Alexander K.; Rijs, Anouk M.; Fischer, Ingo IR/UV Double Resonance Study of the 2-Phenylallyl Radical and its Pyrolysis Products Isolated 2-phenylallyl radicals (2-PA), generated by pyrolysis from a nitrite precursor, have been investigated by IR/UV ion dip spectroscopy using free electron laser radiation. 2-PA is a resonance-stabilized radical that is considered to be involved in the formation of polycyclic aromatic hydrocarbons (PAH) in combustion, but also in interstellar space. The radical is identified based on its gas-phase IR spectrum. Furthermore, a number of bimolecular reaction products are identified, showing that the self-reaction as well as reactions with unimolecular decomposition products of 2-PA form several PAH efficiently. Possible mechanisms are discussed and the chemistry of 2-PA is compared with the one of the related 2-methylallyl and phenylpropargyl radicals. 2023 Chemistry – A European Journal 29 13 urn:nbn:de:bvb:20-opus-312338 10.1002/chem.202202943 Institut für Physikalische und Theoretische Chemie OPUS4-25732 Wissenschaftlicher Artikel Gerlach, Marius; Monninger, Sophie; Schleier, Domenik; Hemberger, Patrick; Goettel, James T.; Braunschweig, Holger; Fischer, Ingo Photoelectron Photoion Coincidence Spectroscopy of NCl\(_{3}\) and NCl\(_{2}\) We investigate NCl\(_{3}\) and the NCl\(_{2}\) radical by photoelectron-photoion coincidence spectroscopy using synchrotron radiation. The mass selected threshold photoelectron spectrum (ms-TPES) of NCl\(_{3}\) is broad and unstructured due to the large geometry change. An ionization energy of 9.7±0.1 eV is estimated from the spectrum and supported by computations. NCl2 is generated by photolysis at 213 nm from NCl\(_{3}\) and its ms-TPES shows an extended vibrational progression with a 90 meV spacing that is assigned to the symmetric N−Cl stretching mode in the cation. An adiabatic ionization energy of 9.94 ± 0.02 eV is determined. 2021 2164–2167 ChemPhysChem 22 21 urn:nbn:de:bvb:20-opus-257322 10.1002/cphc.202100537 Institut für Anorganische Chemie OPUS4-25165 Wissenschaftlicher Artikel Mukhopadhyay, Deb Pratim; Schleier, Domenik; Wirsing, Sara; Ramler, Jaqueline; Kaiser, Dustin; Reusch, Engelbert; Hemberger, Patrick; Preitschopf, Tobias; Krummenacher, Ivo; Engels, Bernd; Fischer, Ingo; Lichtenberg, Crispin Methylbismuth: an organometallic bismuthinidene biradical We report the generation, spectroscopic characterization, and computational analysis of the first free (non-stabilized) organometallic bismuthinidene, BiMe. The title compound was generated in situ from BiMe\(_3\) by controlled homolytic Bi-C bond cleavage in the gas phase. Its electronic structure was characterized by a combination of photoion mass-selected threshold photoelectron spectroscopy and DFT as well as multi-reference computations. A triplet ground state was identified and an ionization energy (IE) of 7.88 eV was experimentally determined. Methyl abstraction from BiMe\(_3\) to give [BiMe(_2\)]• is a key step in the generation of BiMe. We reaveal a bond dissociation energy of 210 ± 7 kJ mol\(^{−1}\), which is substantially higher than the previously accepted value. Nevertheless, the homolytic cleavage of Me-BiMe\(_2\) bonds could be achieved at moderate temperatures (60-120 °C) in the condensed phase, suggesting that [BiMe\(_2\)]• and BiMe are accessible as reactive intermediates under these conditions. 2020 7562-7568 Chemical Science 11 29 urn:nbn:de:bvb:20-opus-251657 10.1039/D0SC02410D Institut für Anorganische Chemie OPUS4-25155 Wissenschaftlicher Artikel Hoche, Joscha; Flock, Marco; Miao, Xincheng; Philipp, Luca Nils; Wenzel, Michael; Fischer, Ingo; Mitric, Roland Excimer formation dynamics in the isolated tetracene dimer The understanding of excimer formation and its interplay with the singlet-correlated triplet pair state \(^{1}\)(TT) is of high significance for the development of efficient organic electronics. Here, we study the photoinduced dynamics of the tetracene dimer in the gas phase by time-resolved photoionisation and photoion imaging experiments as well as nonadiabatic dynamics simulations in order to obtain mechanistic insight into the excimer formation dynamics. The experiments are performed using a picosecond laser system for excitation into the S\(_{2}\) state and reveal a biexponential time dependence. The time constants, obtained as a function of excess energy, lie in the range between ≈10 ps and 100 ps and are assigned to the relaxation of the excimer on the S\(_{1}\) surface and to its deactivation to the ground state. Simulations of the quantum-classical photodynamics are carried out in the frame of the semi-empirical CISD and TD-lc-DFTB methods. Both theoretical approaches reveal a dominating relaxation pathway that is characterised by the formation of a perfectly stacked excimer. TD-lc-DFTB simulations have also uncovered a second relaxation channel into a less stable dimer conformation in the S\(_{1}\) state. Both methods have consistently shown that the electronic and geometric relaxation to the excimer state is completed in less than 10 ps. The inclusion of doubly excited states in the CISD dynamics and their diabatisation further allowed to observe a transient population of the \(^{1}\)(TT) state, which, however, gets depopulated on a timescale of 8 ps, leading finally to the trapping in the excimer minimum. 2021 10 Chemical Science 12 36 11965 11975 urn:nbn:de:bvb:20-opus-251559 10.1039/D1SC03214C Institut für Physikalische und Theoretische Chemie OPUS4-21831 Wissenschaftlicher Artikel Hirsch, Florian; Pachner, Kai; Fischer, Ingo; Issler, Kevin; Petersen, Jens; Mitric, Roland; Bakels, Sjors; Rijs, Anouk M. Do Xylylenes Isomerize in Pyrolysis? We report infrared spectra of xylylene isomers in the gas phase, using free electron laser (FEL) radiation. All xylylenes were generated by flash pyrolysis. The IR spectra were obtained by monitoring the ion dip signal, using a IR/UV double resonance scheme. A gas phase IR spectrum of para-xylylene  was recorded, whereas ortho- and meta-xylylene were found to partially rearrange to benzocyclobutene and styrene. Computations of the UV oscillator strength  for all molecules were carried out and provde an explanation for the observation of the isomerization products. 2020 3 ChemPhysChem 21 14 1515 1518 urn:nbn:de:bvb:20-opus-218316 10.1002/cphc.202000317 Institut für Physikalische und Theoretische Chemie OPUS4-20813 Wissenschaftlicher Artikel Reusch, Engelbert; Holzmeier, Fabian; Gerlach, Marius; Fischer, Ingo; Hemberger, Patrick Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study The reaction products of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gas phase. Aminomethylpyridines were pyrolyzed to initially produce picolyl radicals (m /z =92). At higher temperatures further thermal reaction products are generated in the pyrolysis reactor. All compounds were identified by mass-selected threshold photoelectron spectroscopy and several hitherto unexplored reactive molecules were characterized. The mechanism for several dissociation pathways was outlined in computations. The spectrum of m /z =91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyrroles with adiabatic ionization energies (IE\(_{ad}\)) of 7.99 eV (2-ethynyl-1H -pyrrole) and 8.12 eV (3-ethynyl-1H -pyrrole), and two cyclopentadiene carbonitriles with IE′s of 9.14 eV (cyclopenta-1,3-diene-1-carbonitrile) and 9.25 eV (cyclopenta-1,4-diene-1-carbonitrile). A second consecutive hydrogen loss forms the cyanocyclopentadienyl radical with IE′s of 9.07 eV (T\(_0\)) and 9.21 eV (S\(_1\)). This compound dissociates further to acetylene and the cyanopropynyl radical (IE=9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargyl were identified in the spectra. Computations indicate that dissociation of picolyl proceeds initially via a resonance-stabilized seven-membered ring. 2019 16652-16659 Chemistry - A European Journal 25 72 urn:nbn:de:bvb:20-opus-208132 10.1002/chem.201903937 Institut für Physikalische und Theoretische Chemie OPUS4-20475 Wissenschaftlicher Artikel Schleier, Domenik; Reusch, Engelbert; Lummel, Lisa; Hemberger, Patrick; Fischer, Ingo Threshold photoelectron spectroscopy of IO and IOH Iodine oxides appear as reactive intermediates in atmospheric chemistry. Here, we investigate IO and HOI by mass-selective threshold photoelectron spectroscopy (ms-TPES), using synchrotron radiation. IO and HOI are generated by photolyzing iodine in the presence of ozone. For both molecules, accurate ionization energies are determined, 9.71±0.02 eV for IO and 9.79±0.02 eV for HOI. The strong spin-spin interaction in the 3Σ− ground state of IO+ leads to an energy splitting into the Ω=0 and Ω=±1 sublevels. Upon ionization, the I−O bond shortens significantly in both molecules; thus, a vibrational progression, assigned to the I−O stretch, is apparent in both spectra. 2019 2413-2416 ChemPhysChem 20 19 urn:nbn:de:bvb:20-opus-204751 10.1002/cphc.201900813 Institut für Physikalische und Theoretische Chemie OPUS4-19873 unpublished Röder, Anja; Petersen, Jens; Issler, Kevin; Fischer, Ingo; Mitric, Roland; Poisson, Lionel Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals and Carbenes using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations Reactive hydrocarbon molecules like radicals, biradicals and carbenes are not only key players in combustion processes and interstellar and atmospheric chemistry, but some of them are also important intermediates in organic synthesis. These systems typically possess many low-lying, strongly coupled electronic states. After light absorption, this leads to rich photodynamics characterized by a complex interplay of nuclear and electronic motion, which is still not comprehensively understood and not easy to investigate both experimentally and theoretically. In order to elucidate trends and contribute to a more general understanding, we here review our recent work on excited-state dynamics of open-shell hydrocarbon species using time-resolved photoelectron spectroscopy and field-induced surface hopping simulations, and report new results on the excited-state dynamics of the tropyl and the 1-methylallyl radical. The different dynamics are compared, and the difficulties and future directions of time-resolved photoelectron spectroscopy and excited state dynamics simulations of open-shell hydrocarbon molecules are discussed. 2019 The Journal of Physical Chemistry A urn:nbn:de:bvb:20-opus-198734 Institut für Physikalische und Theoretische Chemie OPUS4-18162 Wissenschaftlicher Artikel Ramler, Jacqueline; Poater, Jordi; Hirsch, Florian; Ritschel, Benedikt; Fischer, Ingo; Bickelhaupt, F. Matthias; Lichtenberg, Crispin Carbon monoxide insertion at a heavy p-block element: unprecedented formation of a cationic bismuth carbamoyl Major advances in the chemistry of 5th and 6th row heavy p-block element compounds have recently uncovered intriguing reactivity patterns towards small molecules such as H\(_2\), CO\(_2\), and ethylene. However, well-defined, homogeneous insertion reactions with carbon monoxide, one of the benchmark substrates in this field, have not been reported to date. We demonstrate here, that a cationic bismuth amide undergoes facile insertion of CO into the Bi-N bond under mild conditions. This approach grants direct access to the first cationic bismuth carbamoyl species. Its characterization by NMR, IR, and UV/vis spectroscopy, elemental analysis, single-crystal X-ray analysis, cyclic voltammetry, and DFT calculations revealed intriguing properties, such as a reversible electron transfer at the bismuth center and an absorption feature at 353 nm ascribed to a transition involving σ- and π-type orbitals of the bismuth-carbamoyl functionality. A combined experimental and theoretical approach provided insight into the mechanism of CO insertion. The substrate scope could be extended to isonitriles. 2019 4169 – 4176 Chemical Science 10 urn:nbn:de:bvb:20-opus-181627 10.1039/C9SC00278B Institut für Anorganische Chemie