[2+2]-cycloadditions of alkenes with the triphenylallenyl cation

The triphenylallenyl cation (8), generated from triphenylpropynol (7) and FSO3H, reacts with alkenes to give the allyl cations 12, which may be deprotonated to yield the methyleneccylobutenes 14. Alternatively, 12 can be converted into the 2-vinyl-indenes 13 two subsequent electrocyclic reactions

Polymere organische Metallkomplexe als organische Leiter

After a short introduction into the field of organic conductors giving as examples stacked charge-transfer complexes and doped polyenes, polymeric macrocyclic metal complexes as organic conductors are discussed in more detail: Beside iodine doped phthalo- cyaninato-IVB-metalloxanes [R4PcMO]n (R = H, tBu) which show conductivities up to 1.4 S.cm-1, the synthesis and characterization of polymeric macrocyclic transition metal complexes shown in fig. 4 with M = Fe, Co and Ru are described. The stacked arrangement of such polymers is achieved by bridging ligands L which can be linked to the central transition metal atom e.g. by two coordinative bonds (type b-polymer) or by one coordinative and one σ-bond (type c-polymer).Numerous examples are described for the type b-polymers e.g. [PcML]n, M = Fe, Co, Ru; L = pyz, dib (fig. 6), which show conductivities up to 0.2 S.cm-1 after doping with iodine.Type c-polymers are synthesized using the cyano group as the bridging ligand: The preparation and characterization of (μ-cyano)-phthalocyaninatometal(III), [PcMCN]n is reported (fig. 7). With M = Co3+ and Fe3+ conductivities up to 10-2 were found without doping

Ab-initio-MO-Studie Methyl- und Phenyl-substituierter Allenyl-Kationen

An den Methyl- und Phenyl-substituierten Allenyl-Kationen 3 - 12 (Tab. 1) wurden ab-initio-MO-Berechnungen unter Verwendung des STO-3G Basissatzes durchgeführt. Die berechneten Bindungslängen und Ladungsverteilungen zeigen Delokalisierung der positiven Ladung an, wie in Formel 1 gezeigt. Mit Hilfe isodesmischer Reaktionen werden Stabilisierungsenergien von Substituenten in 1- und 3-Position ermittelt. Diese Werte ermöglichen in Kombination mit der experimentell bekannten Bildungswärme des Stammkörpers 2 die Bestimmung von H sämtlicher Allenyl-Kationen 3 - 12. Der Vergleich dieser Daten mit einigen experimentell bestimmten Bildungswärmen zeigt Übereinstimmung innerhalb von 2 kcal/mol. Es werden Voraussagen für das Reaktionsverhalten gegenüber n-Nucleophilen und -Systemen gemacht

Analysis of Nociceptive Information Encoded in the Temporal Discharge Patterns of Cutaneous C-Fibers

The generation of pain signals from primary afferent neurons is explained by a labeled-line code. However, this notion cannot apply in a simple way to cutaneous C-fibers, which carry signals from a variety of receptors that respond to various stimuli including agonist chemicals. To represent the discharge patterns of C-fibers according to different agonist chemicals, we have developed a quantitative approach using three consecutive spikes. By using this method, the generation of pain in response to chemical stimuli is shown to be dependent on the temporal aspect of the spike trains. Furthermore, under pathological conditions, gamma-aminobutyric acid resulted in pain behavior without change of spike number but with an altered discharge pattern. Our results suggest that information about the agonist chemicals may be encoded in specific temporal patterns of signals in C-fibers, and nociceptive sensation may be influenced by the extent of temporal summation originating from the temporal patterns.open0

Zwischen nationaler und transnationaler Identität : das Entstehen einer europäischen Öffentlichkeit - Am Beispiel der Berichterstattung des Spiegels und des Economists über die Schuldenkrise in Griechenland

Die Arbeit behandelt das Entstehen einer europäischen Öffentlichkeit und analysiert dazu beispielhaft die Berichterstattung des „Economists“ und des „Spiegels“ über die griechische Schuldenkrise. Im ersten Teil werden die theoretischen Grundlagen gelegt. Verschiedene Modelle und analytische wie normative Theorien von nationaler, transnationaler und europäischer Öffentlichkeit werden erläutert. Außerdem wird der Blick auf den Begriff der kollektiven Identität, die Rolle der Medien sowie die chronologische Entwicklung der Schuldenkrise in Griechenland gelegt. Der zweite, empirische Teil widmet sich der Medieninhaltsanalyse. Artikel, die in den drei Ausgaben zwischen dem 27.06.2015 und dem 11.07.2015 erschienen sind und sich mit der griechischen Schuldenkrise befassen, werden u.a. in Bezug auf die darin zitierten Sprecher, die erwähnten politischen Akteure und ihr Framing untersucht. Abschließend werden die Ergebnisse präsentiert und mit bereits bestehenden Studien verglichen, so dass Aussagen über Tendenzen in der Entstehung einer europäischen Öffentlichkeit getroffen werden können

4,5-Bis(4-meth­oxy­phen­oxy)phthalonitrile

The title compound, C22H16N2O4, was obtained unintentionally as the product of an attempted synthesis of a new phthalocyanine. The dihedral angles formed by the central benzene ring with the aromatic rings of the meth­oxy­phen­oxy groups are 85.39 (5) and 64.19 (5)°

Photophysics and photochemistry of octaglucosylated zinc phthalocyanine derivatives

The ground state electronic absorption spectra, photophysics and photochemistry of amphiphilic octaglucosylated zinc phthalocyanines containing oxygen or sulfur bridges are presented. Triplet quantum yield values for the two dyes (in DMF and DMSO) vary between 0.71 and 0.84, while singlet quantum yield values lie between 0.63 and 0.75. Fluorescence lifetimes were determined experimentally by time correlated single photon counting and semi-empirically by fluorescence quenching techniques; and values from both methods were within the same range. Kinetic data were obtained for the quenching of the triplet state of the phthalocyanines by ground state molecular oxygen; the bimolecular collisional quenching rate constant range between 2.35 × 108 and 1.13 × 109 M-1.s-1. These values suggest that triplet states of the dyes are effectively quenched by ground molecular oxygen

Spectral, photophysical and photochemical properties of tetra-and octaglycosylated zinc phthalocyanines

Photophysical and photochemical properties of a series of tetra- and octaglycosylated zinc phthalocyanines (ZnPcs) substituted with glucose and galactose moieties have been reported. Spectral properties of these phthalocyanines are compared in DMSO. Absorption spectra of the non-peripherally tetra-substituted ZnPcs 2 showed a significant red shift in their Q-band maxima as compared to the peripherally substituted analog 1. All the complexes gave high triplet quantum yields ranging from 0.68 to 0.88, whereas triplet lifetimes were in the range of 100–430 µs in argon-saturated solutions. The octagalactosylated ZnPc 3b showed the highest triplet quantum yield and singlet oxygen quantum yield of 0.88 and 0.69, respectively. The fluorescence quantum yields and lifetimes of all the compounds under investigation were within the range of zinc phthalocyanine complexes

MicroRNA biomarkers as next-generation diagnostic tools for neurodegenerative diseases : a comprehensive review

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells all indicative of disease progression before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, Huntington’s disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or deubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies

On attempts at solvolytic generation of aryl cations

The solvolysis of phenyl triflate (3), phenyl nonaflate (4), o-methylphenyl nonaflate (5), o-cyclopropylphenyl nonaflate (6), o-methoxyphenyl triflate (7), 2,6-dimethoxyphenyl triflate (S), 2,6-diisopropylphenyl triflate (9), 33- dimethoxyphenyl triflate (lo), 3,5-dicyclopropylphenyl triflate (11), 3,5-di(2-methylcyclopropyl)phenyl triflate (12), 2,4,6-tricyclopropylphenyltr iflate (13), and 2,4,6-triisopropylphenytlr iflate (14) were examined in great detail under a wide variety of conditions. In highly polar nonnucleophilic solvents no reaction was observed and the unreacted triflates were recovered quantitatively. In the presence of nucleophiles or nucleophilic solvents the sole products observed were the corresponding phenols. Careful labeling and product studies showed that these phenols arose by nucleophilic attack on sulfur and S-0 bond cleavage. We have not been able to find any evidence for aryl cation intermediates