@phdthesis{HafergebZailer2021,
  author    = {Hafer [geb. Zailer], Elina},
  title     = {Tagging - Development of new qNMR methods},
  doi       = {10.25972/OPUS-21958},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219583},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {High-resolution nuclear magnetic resonance (NMR) spectroscopy is used in structure elucidation and qualitative as well as quantitative examination of product components. Despite the worldwide development of numerous innovative NMR spectroscopic methods, several official methods that analyze specific substances and do not represent a holistic analysis, are still in use for the quality control of drugs, food and chemicals. Thus, counterfeit or contaminated products of inferior quality can be brought onto the market and distributed despite previous quality controls. To prevent this, three NMR spectroscopic methods have been developed within the scope of this work (1) to study the peroxide value in vegetable and animal oils, (2) for the qualitative and quantitative analysis of metal cations and (3) to determine the enantiomeric excess in chiral alcohols. In oil analysis, titration methods are used to determine the bulk quality parameters such as peroxide value, which represents the concentration of peroxides. Titrations show several drawbacks, such as the need of a large amount of sample and solvents, cross reactions and the low robustness. Thus, an alternative NMR spectroscopic method was developed to improve the peroxide analysis by using triphenylphosphine as a derivatization reagent, which reacts with peroxides in a stoichiometric ratio of 1:1 forming triphenylphosphine oxide. In the 1H-31P decoupled NMR spectrum, the signals of the unreacted triphenylphosphine and the reacted triphenylphosphine oxide are detected at 7.4 ppm and 7.8 ppm, respectively. The ratio of the two signals is used for the calculation of the peroxide concentration. 108 oil samples with a peroxide value between 1 meq/kg and 150 meq/kg were examined using the developed method. Oils with a very low peroxide value of less than 3 meq/kg showed a relative standard deviation of 4.9\%, highly oxidized oils with a peroxide value of 150 meq/kg of 0.2\%. The NMR method was demonstrated as a powerful technique for the analysis of vegetable and krill oils. Another 1H NMR spectroscopic method was developed for the qualitative determination of Be2+, Sr2+ and Cd2+, and for the qualitative and quantitative determination of Ca2+, Mg2+, Hg2+, Sn2+, Pb2+ and Zn2+ by using ethylenediamine tetraacetate (EDTA) as complexing agent. EDTA is a hexadentate ligand that forms stable chelate complexes with divalent cations. The known amount of added EDTA and the signal ratio of free and complexed EDTA are used to calculate the concentrations of the divalent cations, which makes the use of an internal standard obsolete. The use of EDTA with Be2+, Sr2+, Cd2+, Ca2+, Mg2+, Hg2+, Sn2+, Pb2+ and Zn2+ result in complexes whose signals are pH-independent, showing cation-specific chemical shifts and couplings in the 1H NMR spectrum that are used for identification and quantification. In the presented NMR method, the limit of quantification of the cations Ca2+, Mg2+, Hg2+, Sn2+, Pb2+, and Zn2+ was determined with 5-22 μg/mL. This method is applicable in the food and drug sectors. The third NMR spectroscopic method introduced an alternative determination of the enantiomer excess (ee) of the chiral alcohols menthol, borneol, 1-phenylethanol and linalool using phosgene as a derivatizing reagent. Phosgene reacts with a chiral alcohol to form carboxylic acid diesters, made of two identical (RR, SS) or two different enantiomers (RS, SR). These two different types of diastereomers can be examined by the difference of their chemical shifts. In the presented method, the integration values of the carbonyl signals in the 13C NMR spectrum are used for the determination of the enantiomer excess. The limit of quantification depends, among others, on the sample and on the non-labelled or 13C-labelled phosgene used for the analysis. In the case of menthol, a quantification limit of ee=99.1\% was determined using non-labelled phosgene and ee=99.9\% using 13C-labelled phosgene. The 13C NMR method was also applied for the quality control of the enantiomeric purity of borneol, 1-phenylethanol and linalool. The developed 13C NMR method represents a powerful alternative to Mosher's reagent for investigating the enantiomeric excess in chiral alcohols. This work demonstrates the variety of possibilities of applications for the quantitative nuclear magnetic resonance spectroscopy in the chemical analysis of drugs, food and chemicals using tagging reactions such as derivatizations and complexations. The nuclear resonance spectroscopic methods developed in this research work represent powerful alternatives to the previously used quality control techniques.},
  subject      = {NMR Spektroskopie},
  language  = {en}
}
@phdthesis{SafontSempere2010,
  author    = {Safont Sempere, Marina Montserrat},
  title     = {Chiral self-sorting of atropo-enantiomeric perylene bisimide dyes},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55359},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {This thesis included the synthesis of conformationally stable chiral perylene bisimide (PBI) dyes, the study of their optical properties in solution and their chiral self-sorting behaviour in nonpolar solvents in which dimerization via pi-pi-stacking takes place. Furthermore, the influence of PBI core chirality on the properties of these dyes in the condensed state has been also studied. We have demonstrated and quantified the prevalence of chiral self-recognition over self-discrimination in pi-stacking dimerization of PBIs. It has been shown that this self-recognition event is compromised by the increasing flexibility of the structures related to the size of the OEG bridging units. Moreover, the inherent chirality of these PBIs has been proven to strongly influence their condensed state properties, for which large differences between the pure enantiomers and the racemates were revealed, as well as between the different bridged macrocyclic PBIs.},
  subject      = {Farbstoff},
  language  = {en}
}
@phdthesis{Lohr2008,
  author    = {Lohr, Andreas},
  title     = {Self-Assembly of Merocyanines : Thermodynamic and Kinetic Insights into the Formation of Well-Defined Dye Aggregates},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28964},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {The present thesis demonstrates the potential of dipolar aggregation of merocyanine dyes as novel directional and specific supramolecular binding motif for the creation of more elaborate supramolecular architectures beyond simple dimers. Furthermore, the self-assembly studies into bis(merocyanine) nanorods gave new insights into the kinetics of morphogenesis in supramolecular aggregates.},
  subject      = {Supramolekulare Chemie},
  language  = {en}
}