@phdthesis{Wirsing2023,
  author    = {Wirsing, Sara},
  title     = {Computational Spectroscopic Studies with Focus on Organic Semiconductor Systems},
  doi       = {10.25972/OPUS-28655},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286552},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {This work presents excited state investigations on several systems with respect to experimental spectroscopic work. The majority of projects covers the temporal evolution of excitations in thin films of organic semiconductor materials. In the first chapters, thinfilm and interface systems are build from diindeno[1,2,3-cd:1',2',3'-lm]perylene (DIP) and N,N'-bis-(2-ethylhexyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDIR-CN2) layers, in the third chapter bulk systems consist of 4,4',4"-tris[(3-methylphenyl)phenylamino] triphenylamine (m-MTDATA), 4,7-diphenyl-1,10-phenanthroline (BPhen) and tris-(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB). These were investigated by aggregate-based calculations. Careful selection of methods and incorporation of geometrical relaxation and environmental effects allows for a precise energetical assignment of excitations. The biggest issue was a proper description of charge-transfer excitations, which was resolved by the application of ionization potential tuning on aggregates. Subsequent characterization of excitations and their interplay condenses the picture. Therefore, we could assign important features of the experimental spectroscopic data and explain differences between systems. The last chapter in this work covers the analysis of single molecule spectroscopy on methylbismut. This poses different challenges for computations, such as multi-reference character of low-lying excitations and an intrinsic need for a relativistic description. We resolved this by combining complete active space self-consistent field based methods with scalarrelativistic density-functional theory. Thus we were able to confidently assign the spectroscopic features and explain underlying processes.},
  subject      = {Theoretische Chemie},
  language  = {en}
}
@phdthesis{Schinzel2009,
  author    = {Schinzel, Sandra},
  title     = {Quantum Chemical Investigations of Structure, Bonding and EPR Parameters of Manganese Complexes relevant to Photosystem II},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-35320},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Im Wasser-oxidierenden Cluster („oxygen-evolving complex", OEC) des Photosystem II findet sich die prim{\"a}re Quelle der Sauerstoffproduktion der Erde. Der OEC katalysiert in gr{\"u}nen Pflanzen unter Absorption von Sonnenlicht die Vierelektronen-Oxidation von Wasser zu Sauerstoff in einer zyklischen Sequenz von Oxidationszust{\"a}nden (Kok-Zyklus). In dieser Arbeit wurden Strukturen, Spindichteverteilungen sowie EPR-Parameter ein-, zwei- und vierkerniger Mangankomplexe, die in Bezug auf den OEC modelliert wurden, mit Hilfe der Dichtefunktionaltheorie (DFT) berechnet. Hauptziel war das Verst{\"a}ndnis der molekularen und elektronischen Struktur des vierkernigen Manganclusters des OEC durch direkten Vergleich mit experimentellen EPR-Daten.},
  subject      = {DFT},
  language  = {en}
}
@phdthesis{Remenyi2006,
  author    = {Remenyi, Christian},
  title     = {Density Functional Studies on EPR Parameters and Spin-Density Distributions of Transition Metal Complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-19848},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {In dieser Arbeit wurden EPR-Parameter und Spindichteverteilungen von {\"U}bergangsmetallkomplexen mit Hilfe der Dichtefunktionaltheorie (DFT) berechnet. Um das Potential der DFT bei der Beschreibung solcher Systeme zu zeigen, wurden mehrere Validierungsstudien durchgef{\"u}hrt, die in den Kapiteln 3-5 vorgestellt werden. Die Kapitel 6-8 besch{\"a}ftigen sich dagegen eher mit konkreten chemischen Fragestellungen, die einige biologisch relevante {\"U}bergangsmetallkomplexe betreffen.},
  subject      = {Dichtefunktionalformalismus},
  language  = {en}
}
@phdthesis{Pavel2003,
  author    = {Pavel, Ioana-Emilia},
  title     = {Vibrational spectroscopy and density functional theory calculations, a powerful approach for the characterization of pharmaceuticals and new organometallic complexes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-7186},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2003},
  abstract  = {In the current work, several well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) and new organometallic compounds (nickel(II) cupferronato complexes NiL2An, L = PhN2O2-, n = 1, A = o-phenanthroline (1), o,o'-bipyridine (2) and n = 2, A = H2O (3), o-NH2Py (4), o-C6H4(NH2)2 (5); silylene-bridged dinuclear iron complexes [Cp(OC)2Fe]2SiX2 (X = H (6), F (7), Cl (8), Br (9), I (10)); 3-silaoxetane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-oxa-3-silacyclobutane (11) and 3-silathietane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-sila-3-thiacyclobutane (12) compounds), which have successfully been characterized by using vibrational spectroscopy in conjunction with accurate density functional theory (DFT) calculations, are presented. The DFT computed molecular geometries of the species of interest reproduced the crystal structure data very well and in conjunction with IR and Raman measurements helped us to clarify the structures of the compounds, for which no experimental data were available; and this, especially for the new organometallic compounds, where the X-Ray analysis was limited by the non-availability of single crystals (3, 5, 10). Furthermore, a natural population analysis (NPA) and natural bond orbital (NBO) calculations together with a detailed analysis of the IR and Raman experimental as well as calculated spectra of the new organometallic compounds, allowed us to study some special bonding situations (1-12) or to monitor the structural changes observed with the change in temperature during the Raman experiments (11, 12). By combining these two methods (DFT and vibrational spectroscopy), the auspicious results obtained on the organometallic compounds 6-12 and overall in literature, made us confident of the power of theoretical calculations in aiding the interpretation of rich SERS spectra by solving some interesting issues. Consequently, the Raman and SERS spectra of well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) or new potentially biological active organometallic complexes (1-5), that were synthetized by our coworkers, were discussed with the assistance of the accurate results obtained from DFT calculations (structural parameters, harmonic vibrational wavenumbers, Raman scattering activities), and many previous incomplete assignments have been analyzed and improved. This allowed us to establish the vibrational behavior of these biological compounds near a biological artificial model at different pH values or concentrations (Ag substrate), taking into account that information about the species present under particular conditions could be of great importance for the interpretation of biochemical processes. The total electron density of molecules and the partial charges situated on selected atoms, which were determined theoretically by NPA, allowed us to establish the probability of different atoms acting as an adsorptive site for the metal surface. Moreover, a closer examination of the calculated orbitals of molecules brought further arguments on the presence or absence of the photoproducts at the Ag surface during the irradiation (1,4-dihydrazinophthalazine sulfate). Overall, the results provide a benchmark illustration of the virtues of DFT in aiding the interpretation of rich vibrational spectra attainable for larger polyatomic adsorbates by using SERS, as well as in furnishing detailed insight into the relation between the vibrational properties and the nature of the Ag substrate-adsorbate bonding. Therefore, we strongly believe that theoretical calculations will become a matter of rapidly growing scientific and practical interest in SERS.},
  subject      = {Arzneimittel},
  language  = {en}
}
@phdthesis{Moigno2001,
  author    = {Moigno, Damien},
  title     = {Study of the ligand effects on the metal-ligand bond in some new organometallic complexes using FT-Raman and -IR spectroscopy, isotopic substitution and density functional theory techniques},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-3101},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2001},
  abstract  = {The present studies which have been performed in the work-group C-2 (Prof. W. Kiefer) within the program of the Sonderforschungsbereichs 347, deal with the FT-Raman and -IR spectroscopy on new organometallic complexes, synthesized in the work-groups B-2 (Prof. W. Malisch), B-3 (Prof. W. A. Schenk), D-1 (Prof. H. Werner) and D-4 (Prof. D. Stalke). The FT-Raman spectra recorded at 1064 nm led to very useful and interesting information. Furthermore, the DFT calculations which are known to offer promise of obtaining accurate vibrational wavenumbers, were successfully used for the assignment of the vibrational spectra. For the first time it has been possible to ascribe exactly the n(RhC) stretching mode in the vinylidene rhodium(I) complex trans-[RhF(=C=CH2)(PiPr3)2] by using isotopic substitution, in conjunction with theoretical calculations. This is also true for the complexes trans-[RhF(CO)(PiPr3)2], trans-[RhF(C2H4)(PiPr3)2], trans-[RhX(=C=CHPh)(PiPr3)2] (X = F, Cl, Br, I, Me, PhCºC) and trans-[RhX(CN-2,6-xylyl)(PiPr3)2] (X = F, Cl, Br, I, CºCPh). In addition, the comparison between the n(RhC) wavenumbers of the complexes trans-[RhF(=13C=13CH2)(PiPr3)2] and trans-[RhF(CO)(PiPr3)2], containing the isoelectronic ligands 13C=13CH2 and CO, which have the same reduced mass, indicated that the Rh-C bond is stronger in the carbonyl than in the vinylidene complex. Besides, the n(RhF) stretching mode, which has been observed at higher wavenumbers in the FT-Raman and -IR spectra of trans-[RhF(CO)(PiPr3)2], showed that the carbonyl ligand is a better p-acceptor and a less effective s-donor than the vinylidene one. Moreover, the comparison of the n(CºC) and n(Rh-C) modes from the FT-Raman spectrum of the complexes trans-[Rh(CºCPh)(L)(PiPr3)2] (L = C=CHPh, CO, CN-2,6-xylyl) point out that the p-acceptor ability of the ligand trans to CºCPh should rise in the order C=CH2 < CO < CN-2,6-xylyl \pounds C=CHPh. The investigated sensitivity of the n(RhC), n(CC), n(CO) and n(CN) vibrational modes to the electronic modifications occuring in the vinylidene, carbonyl, ethylene and isonitrile complexes, should allow in the future the examination of the p-acceptor or p-donor properties of further ligands. Likewise, we were able to characterize the influence of various X ligands on the RhC bond by using the n(RhC) stretching mode as a probe for the weakening of this. The calculated wavenumbers of the n(RhC) for the vinylidene complexes trans-[RhX(=C=CHR)(PiPr3)2], where R = H or Ph, suggested that the strength of the Rh=C bond increases along the sequence X = CºCPh < CH3 < I < Br < Cl < F. For the series of carbonyl compounds trans-[RhX(CO)(PiPr3)2], where X = F, Cl, Br and I, analogous results have been obtained and confirmed from the model compounds trans-[RhX(CO)(PMe3)2]. Since, the calculated vibrational modes for the ethylene complex trans-[RhF(C2H4)(PiPr3)2] were in good agreement with the experimental results and supported the description of this complex as a metallacyclopropane, we were interested in getting more information upon this class of compounds. In this context, we have recorded the FT-Raman and -IR spectra of the thioaldehyde complexes mer-[W(CO)3(dmpe)(h2-S=CH2)] and mer-[W(CO)3(dmpe)(h2-S=CD2)] which have been synthezised by B-3. The positions of the different WL vibrational modes anticipated by the DFT calculations, were consistent with the experimental results. Indeed, the analysis of the band shifts in the FT-Raman and -IR spectra of the isotopomer mer-[W(CO)3(dmpe)(h2-S=CD2)] confirmed our assignment. The different stereoisomers of complex mer-[W(CO)3(dmpe)(h2-S=CH2)] were investigated too, since RMN and IR-data have shown that complex mer-[W(CO)3(dmpe)(h2-S=CH2)] lead in solution to an equilibrium. Since the information on the vibrational spectra of the molybdenum and tungsten complexes Cp(CO)2M-PR2-X (M = Mo, W; R = Me, tBu, Ph; X = S, Se) is very scarce, we extended our research work to this class of compounds. We have tried to elucidate the bonding properties in these chalcogenoheterocycle complexes by taking advantage of the mass effect on the different metal atoms (W vs. Mo). Thus, the observed band shifts allowed to assign most of the ML fundamental modes of these complexes. This project and the following one were a cooperation within the work-group B-2. The Raman and IR spectra of the matrix isolated photoproducts expected by the UV irradiation of the iron silyl complex Cp(CO)2FeSiH2CH3 have been already reported by Claudia Fickert and Volker Nagel in their PhD-thesis. Since no exact assignment was feasible for these spectra, we were interested in the study of the reaction products created by irradiation of the carbonyl iron silyl complex Cp(CO)2FeCH2SiH3. Although the calculated characteristic vibrational modes of the metal ligand unit for the various photoproducts are significantly different in constitution, they are very similar in wavenumbers, which did not simplify their identification. However, the theoretical results have been found to be consistent with the earlier experimental results. Finally, the last part of this thesis has been devoted to the (2-Py)2E- anions which exhibit a high selectivity toward metal-coordination. All di(2-pyridyl) amides and -phosphides which were synthesized by D-4, coordinate the R2Al+ fragment via both ring nitrogen atoms. This already suggests that the charge density in the anions is coupled into the rings and accumulated at the ring nitrogen atoms, but the Lewis basicity of the central nitrogen atom in Et2Al(2-Py)2N is still high enough to coordinate a second equivalent AlEt3 to form the Lewis acid base adduct Et2Al(2-Py)2NAlEt3. Due to the higher electronegativity of the central nitrogen atom in Me2Al(2-Py)2N, Et2Al(2-Py)2N and Et2Al(2-Py)2NAlEt3, compared to the bridging two coordinated phosphorus atom in Me2Al(2-Py)2P and Et2Al(2-Py)2P, the di(2-pyridyl)amide is the hardest Lewis base. In the phosphides merely all charge density couples into the rings leaving the central phosphorus atom only attractive for soft metals. These results were confirmed by using DFT and MP2 calculations. Moreover, a similar behaviour has been observed and described for the benzothiazolyl complex [Me2Al{Py(Bth)P}], where complementary investigations are to be continued. The DFT calculations carried out on the model compounds analysed in these studies supply very accurate wavenumbers and molecular geometries, these being in excellent agreement with the experimental results obtained from the corresponding isolated complexes.},
  subject      = {{\"U}bergangsmetallkomplexe},
  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}
}
@phdthesis{Kacprzak2006,
  author    = {Kacprzak, Sylwia},
  title     = {Investigations of the EPR parameters of bioradicals by density functional methods},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-19108},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {Die quantenchemische Modellierung von Parametern der elektronenparamagnetischen Resonanz (EPR) stellt, in Kombination mit Daten aus modernen Hochfeld-/Hochfrequenz (HF) EPR-Techniken, eine {\"u}beraus wichtige analytische Methode dar, um Einblicke in die Radikal-Protein-Wechselwirkung zu gewinnen. Diese Wechselwirkung bestimmt zu einem großen Teil die Abl{\"a}ufe radikalischer biochemischer Prozesse. In dieser Arbeit untersuchten wir in einer Reihe von Dichtefunktionaltheorie (DFT)-Studien die EPR-Parameter diverser biologisch wichtiger Radikale sowie mehrerer durch Radikal-Protein-Wechselwirkungen im Photosystem I inspirierter Modellsysteme. Wir demonstrierten die Genauigkeit sowie die Kapazit{\"a}t unserer Methode, um Einblicke in die in vivo Umgebung und Reaktivit{\"a}t von Bioradikalen zu erhalten. Unser DFT-Ansatz zur Berechnung elektronischer g-Tensoren wurde auf Semichinonradikalanionen in verschiedenen Proteinumgebungen photosynthetischer Reaktionszentren angewandt. Supermolekulare Modelle wurden, basierend auf einer Kombination aus kristallographischen und quantenchemischen Strukturdaten, f{\"u}r die aktiven Zentren QA und QB bakterieller Reaktionszentren, f{\"u}r A1 des Photosystems I sowie f{\"u}r Ubisemichinon in gefrorenem 2-Propanol erstellt. Nach der Skalierung der berechneten \&\#8710;gx Komponenten um 0.92 stimmen die auf gradienten-korrigertem DFT-Niveau mit den bestenverf{\"u}gbaren Spin-Bahn-Operatoren berechneten Komponenten \&\#8710;gx sowie \&\#8710;gy mit den Hochfeld-EPR-Referenzdaten innerhalb der experimentellen Genauigkeit in allen vier untersuchten Systemen {\"u}berein. Der Einfluss verschiedener nichtkovalenter Wechselwirkungen zwischen dem Semichinon und dem Protein wurde durch das sukzessive Verkleinern der Modellsysteme studiert. Dabei wurde festgestellt, dass der Effekt der Wasserstoffbr{\"u}ckenbindung zu den beiden Carbonyl-Sauerstoff-Atomen der Semichinone wegen der kompensierenden Spinpolarisationseffekte nicht additiv ist. Der Effekt der Tryptophan-Semichinon \&\#61552;-Stapelung hat auf QA und A1 unterschiedliche Auswirkungen. Dies konnte auf die andersartige Ausrichtung der wechselwirkenden Fragmente sowie auf die unterschiedliche Spinpolarisation zur{\"u}ckgef{\"u}hrt werden. Im n{\"a}chsten Teil dieser Arbeit wurden Semichinone der so genannten „hoch-affinen" Bindungsstelle der Chinoloxidase (QH) untersucht. Vor kurzem durchgef{\"u}hrte Multifrequenz-EPR-Studien der QH der Chinoloxidase legten asymmetrische Wasserstoffbr{\"u}ckenbindungen zum Semichinonradikalanion nahe. Eine einzelne Wasserstoffbr{\"u}ckenbindung zum O1 des Carbonyls war ein weiteres vorgeschlagenes Strukturmerkmal, das allerdings im Gegensatz zu fr{\"u}heren experimentellen Hinweisen st{\"u}nde. Wir haben DFT Berechnungen der EPR-Parameter (g-Tensoren, 13C-, 1H- und 17O-Hyperfeinkopplungstensoren) einer großen Anzahl von supermolekularen Modellkomplexen durchgef{\"u}hrt, um detaillierte Einblicke in die Zusammenh{\"a}nge zwischen Struktur, Umgebung und EPR-Parametern von Ubisemichinon-Radikalanionen zu gewinnen. Ein Bindungsmodell, das nur eine einzige Wasserstoffbr{\"u}cke ber{\"u}cksichtigt, ist demnach weder in der Lage, die experimentell beobachteten niedrigen gx-Komponenten der g-Tensoren, noch die beobachtete große Asymmetrie von 13C-Carbonyl HFC-Tensoren zu erkl{\"a}ren. Basierend auf einem detaillierten Vergleich zwischen Rechnung und Experiment wurde ein Modell mit zwei Wasserstoffbr{\"u}ckenbindungen zu O1 und einer Wasserstoffbr{\"u}ckenbindung zu O4 f{\"u}r QH vorgeschlagen. Ein Modell mit jeweils einer Wasserstoffbr{\"u}ckenbindung mehr kann jedoch ebenfalls nicht v{\"o}llig ausgeschlossen werden. Zus{\"a}tzlich wurden weitere erkannte Zusammenh{\"a}nge zwischen EPR-Parametern und Wasserstoffbr{\"u}ckenbindungen von Ubisemichinonen in Proteinen diskutiert. Theoretische Untersuchungen bez{\"u}glich des Mechanismus des Elektronentransfers im Photosystem I gaben den Anstoß, relativ kleine rotierende molekulare Motoren, bestehend aus intramolekular verbundenen Dyaden, welche eine Chinoneinheit sowie eine Pyrrol- oder Indoleinheit verkn{\"u}pfen, zu modellieren. Die Berechnungen zeigten, dass f{\"u}r einige Systeme, abh{\"a}ngig von der L{\"a}nge und den Ankn{\"u}pfungspunkten der verbundenen Ketten, eine Reduktion des Chinons zum Semichinonradikalanion oder Chinolatdianion mit einer reversiblen intramolekularen Neuorientierung weg von einer \&\#61552;-Stapelung und hin zu einer T-Stapelung auftritt. Durch die Umstrukturierung wird eine Wasserstoffbr{\"u}ckenbindung der Pyrrol- oder Indol-N-H-Funktion zum Semichinon- oder Chinolat-\&\#61552;-Systems nach der Reduktion ausgebildet. In einigen Systemen bilden sich jedoch Wasserstoffbr{\"u}ckenbindungen zum Semichinon- oder Chinolat-Sauerstoffatom aus, die gegen{\"u}ber der T-Stapelung bevorzugt werden. Die intramolekularen Wechselwirkungen ver{\"a}ndern das Redoxpotential des Chinons. Der elektronische g-Tensor, welcher f{\"u}r die Semichinone berechnet wurde, beweist eindeutig das Vorhandensein dieser Wasserstoffbr{\"u}ckenbindung zum Semichinon. g-Tensoren stellen somit eine geeignete Kenngr{\"o}ße in der EPR Spektroskopie dar, um strittige Strukturen aufzukl{\"a}ren. Wir halten auch einen intramolekularer Protonentransfer im dianionischen Zustand f{\"u}r m{\"o}glich. Im Gegensatz zu Semichinonen welche paramagnetische Zust{\"a}nde von Enzymen-Cofaktoren darstellen sind Glyclradikale echte Proteinradikale. Als Schritt zum tiefer gehenden Verst{\"a}ndnis von EPR-Parametern des Glycylradikals in Proteinen wurden die Hyperfeinkopplungstensoren und insbesondere der g-Tensor des N-Acetylglycyls durch systematische hochgenaue quantenchemischen Berechnungen an diversen geeigneten Modellsystemen untersucht. Die quantitative Berechnung von g-Tensoren f{\"u}r solche Glycyl-{\"a}hnlichen Radikale ist eine enorme Herausforderung, insbesondere wegen der sehr kleinen g-Anisotropie. Diese ist zudem mit einer nichtsymmetrischen delokalisierten Spindichteverteilung auf verschiedene Atome des Molek{\"u}ls verbunden, die mit vergleichbaren Spinbahneffekten zum g-Tensor beitragen. Die Wahl eines geeigneten Eichursprungs des magnetischen Vektorpotentials und geeigneter Spin-Bahn-Operatoren, gestaltete sich weitaus anspruchsvoller als in vorausgegangen Arbeiten zu g-Tensoren organischer Radikale. Umgebungseffekte, die durch supermolekulare Wasserstoffbr{\"u}ckenbindungs-Modelle ber{\"u}cksichtigt wurden, stellen sich hingegen als nicht so schwerwiegend heraus, zum Teil durch die gegenseitige Kompensierung des Einflusses von intramolekularen und intermolekularen Wasserstoffbr{\"u}ckenbindungen. Den gr{\"o}ßten Einfluss auf den g-Tensor {\"u}bt die Konformation des Radikals aus. Die angewendete DFT Methode {\"u}bersch{\"a}tzt systematisch sowohl die \&\#8710;gx als auch die \&\#8710;gy Komponente des g-Tensors. Dieses Ergebnis ist wichtig f{\"u}r Untersuchungen von Protein-Glycyl-Radikalen (siehe weiter unten). Die 1H\&\#61537; und 13C\&\#61537; Hyperfeinkopplungen h{\"a}ngen nur wenig von den gew{\"a}hlten supermolekularen Modellen ab und scheinen weniger empfindlich gegen{\"u}ber der genauen Struktur und Umgebung des Molek{\"u}ls zu sein. Die Anzahl der bekannten Enzyme, die als funktionelle Gruppe ein Glycyl-Radikal besitzen, wird immer gr{\"o}ßer. Wir f{\"u}hrten in dieser Arbeit eine systematische quantenchemische Studie zur Spindichteverteilung, elektronischem g-Tensor und Hyperfeinkopplungskonstanten diverser Modelle von Protein-gebundenen Glycylradikalen durch. Wie schon bei N-Acetylglycyl gesehen (siehe oben) stellt auch hier die geringe g-Anisotropie dieses delokalisierten, asymmetrischen Systems selbst f{\"u}r moderne Rechenmethoden eine betr{\"a}chtliche Herausforderung dar. Dies betrifft zum einen die Qualit{\"a}t der Strukturoptimierung, zum anderen die Wahl des Spin-Bahn-Operators und des Eichursprungs des magnetischen Vektorpotentials. Umgebungseffekte aufgrund der Ausbildung von Wasserstoffbr{\"u}ckenbindungen h{\"a}ngen in komplizierter Weise von den verschiedenen intramolekularen Wasserstoffbr{\"u}ckenbindungen verschiedener Konformationen des Radikals ab. Die jeweilige Konformation hat insgesamt gesehen die gr{\"o}ßte Auswirkung auf den berechneten g-Tensor (jedoch weniger auf den Hyperfeinkopplungstensor). Wir diskutierten dies im Zusammenhang verschiedener g-Tensoren, welche vor kurzem durch Hochfeld-EPR Messungen f{\"u}r drei verschiedene Enzyme erhalten wurden. Basierend auf den Resultaten der Kalibrierungsstudie an N-Acetylgylcyl, schlagen wir vor, dass das Glycylradikal, welches f{\"u}r die E.coli anaerobische Ribonucleotid Reductase (RNR) beobachtet wurde, eine gestreckte Konformation besitzt, die sich von derjenigen der entsprechenden Radikale der Pyruvat Format-Lyase (PFL) oder Benzylsuccinatsynthase (BSS) unterscheidet.},
  subject      = {Biologisches System},
  language  = {en}
}
@article{HagspielArrowsmithFantuzzietal.2021,
  author    = {Hagspiel, Stephan and Arrowsmith, Merle and Fantuzzi, Felipe and Vargas, Alfredo and Rempel, Anna and Hermann, Alexander and Br{\"u}ckner, Tobias and Braunschweig, Holger},
  title     = {Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates},
  series = {Angewandte Chemie International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie International Edition},
  number    = {12},
  doi       = {10.1002/anie.202015508},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256432},
  pages     = {6446-6450},
  year      = {2021},
  abstract  = {Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.},
  language  = {en}
}
@phdthesis{Hagspiel2022,
  author    = {Hagspiel, Stephan Alexander},
  title     = {Synthesis and Reactivity of Pseudohalide-substituted Boranes and Borylenes},
  doi       = {10.25972/OPUS-24945},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-249459},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {This work involves the synthesis and reactivity of pseudohalide-substituted boranes and borylenes. A series of compounds of the type (CAAC)BR2Y (CAAC = cyclic alkyl(amino)carbene; R = H, Br; Y = CN, NCS, PCO) were prepared first. The two-electron reduction of (CAAC)BBr2Y (Y = CN, NCS) in the presence of a second Lewis base L (L = N-heterocyclic carbene) resulted in the formation of the corresponding doubly Lewis base-stabilized pseudohaloborylenes (CAAC)(L)BY. These borylenes show versatile reactivity patterns, including their oxidation to the corresponding radical cations, coordination via the respective pseudohalide substituent to group 6 metal carbonyl complexes, as well as a boron-centered protonation with Br{\o}nsted acids to boronium cations. Reduction of (CAAC)BBr2(NCS) in the absence of a second donor ligand, led to the formation of boron-doped thiazolothiazoles via reductive dimerization of two isothiocyanatoborylenes. These B,N,S-heterocycles possess a low degree of aromaticity as well as interesting photophysical properties and can furthermore be protonated as well as hydroborated. Additionally, CAAC adducts of the parent boraphosphaketene (CAAC)BH2(PCO) could be prepared, which readily reacted with boroles [Ph4BR'] (R' = aryl) via decarbonylation in a ring expansion reaction. The obtained 1,2-phosphaborinines represent B,P-isosteres of benzene and consequently could be coordinated to metal carbonyl complexes of the chromium triade via η6-coordination, resulting in new half-sandwich complexes thereof.},
  subject      = {Borylene},
  language  = {en}
}
@article{BruecknerHessStennettetal.2021,
  author    = {Br{\"u}ckner, Tobias and Heß, Merlin and Stennett, Tom E. and Rempel, Anna and Braunschweig, Holger},
  title     = {Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond},
  series = {Angewandte Chemie, International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie, International Edition},
  number    = {2},
  doi       = {10.1002/anie.202012101},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240669},
  pages     = {736-741},
  year      = {2021},
  abstract  = {An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit.},
  language  = {en}
}