Application of quantum-chemical methods including density functional theory for the interpretation of isotropic hyperfine data. The example of azulenebenzoquinone

The radical anion of aceneazulenedione in which a benzoquinone is fused to an azulene moiety was generated by electrolysis and by reduction with the alkali metals in ethereal solvents. The hyperfine data could not be reproduced by standard Hückel calculations which usually give reliable predictions for the spin distribution in radical ions such as azulene quinones and a variety of extended π systems. However, PPP and, preferably,ab initio geometry optimisations followed by single-point calculations of the Fermi contact interaction with density functional theory, led to a straightforward assignment of the hyperfine coupling constant

Electronic money

V této bakalářské práci jsou popsány systémy elektronických peněz, které využívají kryptografické prostředky jako symetrické a asymetrické šifry, digitální podpis a hashovací funkci. Popis těchto technik je klíčový k pochopení, jak fungují systémy elektronických peněz. Dále jsou popsány tři systémy elektronických peněz v ČR.In this bachelor thesis are described electronic money systems, which uses cryptography techniques such as symmetric and asymmetric ciphers, digital sign and hash function. Describing those techniques is crucial for understanding how electronic money systems works. Then three electronic money systems from Czech republic are briefly described.

Ligand spheres in asymmetric hetero Diels-Alder reactions catalyzed by Cu(II) box complexes: experiment and modeling

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The stereoselective hetero Diels–Alder reaction between ethyl glyoxylate and cyclohexadiene catalyzed by [Cu(II)t-Bu-(box)](OTf)2 was investigated. The reaction was performed step-by-step and the geometry of the Cu(II) complexes formed in the course of the catalysis was analysed by EPR spectroscopy, advanced pulsed EPR methods (ENDOR, and HYSCORE) and DFT calculations. Our results show that one triflate counterion is directly coordinated to Cu(II) during the catalytic process (axial position). This leads to penta-coordinated Cu(II) complexes. Solvent molecules are able to alter the geometry of the Cu(II) complexes although their coordination is weak. These findings provide an explanation for the solvent and counterion effects observed in many catalytic reactions

ESR and ENDOR study on the radical ions of two non—alternant hydrocarbons: 1,3,5,7-tetra-tert-butyl-s-indacene and 2,7-di-tert-butyldicyclopenta [a,e] cyclooctene

The radical anions and radical cations of two alkyl-substituted non-alternant hydrocarbons, 1,3,5,7-tetra-tert-butyl-s-indacene and 2,7-di-tert-butyldicyclopenta [a,e] cyclooctene, were characterized by their proton coupling constants with the use of ESR and, in part, ENDOR spectroscopy. Considering the unusual electronic structures of the π-systems in question, these values agree fairly well with those predicted by simple MO theory. Also reported are the proton hyperfine data for the radical ions of the likewise alkyl-substituted non-alternant 8,16-diisopropyl-s-indaceno [1,2,3-cd:5,6,7-c′ d′] diphenalene

Hydrogen Abstraction from the C15 Position of the Cholesterol Skeleton

[EN] Cholesterol (Ch) is an integral part of cell membrane, where it is prone to oxidation. In humans, oxidation of Ch is commonly linked to various pathologies like Alzheimer's disease, atherosclerosis, and even cancer, which proceed via mechanisms involving enzymatic and free radical pathways. The latter begin with hydrogen abstraction (HA) from Ch by a reactive free radical. It has been established that the most efficient HA from Ch occurs at C7, although HA from C4 by peroxyl radicals has recently been observed. Conversely, HA from Ch positions other than the thermodynamically preferred C7 or C4 has never been reported. We have designed a Ch derivative where a benzophenone moiety is linked to C7 by a covalent bond. This mirrors a specific orientation of Ch within a confined environment. Product analysis and time-resolved spectroscopic studies reveal an unprecedented HA from C15, which is a thermodynamically unfavorable position. This indicates that a specific topology of reactants is crucial for the reactivity of Ch. The relative orientation of the reactants can also be relevant in biological membranes, where Ch, polyunsaturated fatty acids, and numerous oxidizing species are confined in highly restricted and anisotropic environments.This work was supported by the Carlos III Institute of Health (Grants No. PII6/01877, "Miguel Servet fellowship" CPII16/00052 to I.A.), and by the Generalitat Valenciana (Prometeo 2017/075). We would like to thank Dr Fedora Grande for sending an exchange student (M.B.). D.N. and G.G. thank NAWI Graz for support.Palumbo, F.; Andreu Ros, MI.; Brunetti, M.; Schmallegger, M.; Gescheidt, G.; Neshchadin, D.; Miranda Alonso, MÁ. (2019). Hydrogen Abstraction from the C15 Position of the Cholesterol Skeleton. The Journal of Organic Chemistry. 84(23):15184-15191. https://doi.org/10.1021/acs.joc.9b02181S15184151918423Zerbinati, C., & Iuliano, L. (2017). 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Radical Ions in the Pentalene Series. Part III. Three Paramagnetic Redox Stages of a Dicyclopenta[a,e]pentalene

Five redox stages have been observed for the recently synthesized 1,3,5,7-tetra(tert-butyl) derivative 1 of the dicyclopenta[a,e]pentalene, a novel non-alternant hydrocarbon: the radical cation 1 , the neutral compound 1, the radical anion Is, the dianion 1²-, and the radical trianion 1³. Information about the electronic structure of the three paramagnetic stages, 1, 1⁻, and 1³⁻ is provided by the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The unpaired electron in the trianion resides mainly on the ‘inner’ butadiene-π-system, whereas in the cation and the anion, it is largely localized on the two ‘outer’ five-membered rings

Biologically Relevant Small Radicals

Biologically relevant small radicals are at the focus of the working group 4 (WG4) of the COST Action CM0603 (Free Radicals in Chemical Biology, CHEMBIORADICAL). This article surveys the areas of research being undertaken by the partners in WG4. The character of the radicals is described together with experimental techniques utilized to follow their structure and reactivity. Specifically, C-, S-, N- and O-centered radicals of small size, and their interaction with different biomolecules are described. Processes at the molecular level exemplifying important biological signaling and damaging pathways are introduced

Functional anatomy of outcome evaluation during Iowa Gambling Task performance in patients with Parkinson's disease: an fMRI study

Abstract The aim of this study was to investigate the functional anatomy of decision-making during the Iowa Gambling Task in patients with Parkinson's disease. We used event-related functional magnetic resonance imaging (fMRI) during a computerized version of IGT to compare 18 PD patients on dopaminergic medication in the ON state and 18 healthy control subjects. Our analyses focused on outcome evaluation following card selection, because we expected this aspect of decision-making to be impaired in PD patients. The PD patients exhibited lower activation of the left putamen than the control group as a reaction to penalty. Using psychophysiological interaction analysis, we identified decreased functional connectivity between the right globus pallidus internus and the left anterior cingulate gyrus in the PD group. In contrast, increased connectivity between these structures was observed after penalty in the control group. Our results suggest altered functioning of the basal ganglia and their connections with the cortical structures involved in the limbic loop (e.g., the limbic fronto-striatal circuit of the basal ganglia) during decision-making in PD patients. Differences in the response to loss could be associated with insufficient negative reinforcement after a loss in PD patients in the ON state in comparison to a healthy population