Steuerung der Elektronendonor- und Akzeptoreigenschaften von guanidino-funktionalisiertem Phenazin in di- und tetranuklearen Übergangsmetallkomplexen

Intramolekulare Elektronentransferprozesse in Übergangsmetallkomplexen sind nicht nur in der Grundlagenforschung, sondern ebenso für die Forschung in der Katalyse oder den Materialwissenschaften von Interesse. In dieser Dissertation wurden die Möglichkeiten zur Einflussnahme auf die Grenzorbitalenergien von guanidino-funktionalisiertem Phenazin in freier Form sowie in zwei- und vierkernigen Übergangsmetallkomplexen untersucht. Dabei wurden insbesondere die Bedingungen, die zu einem intramolekularen Elektronentransfer führen, betrachtet. Bei der Verbindung 2,3,7,8-Tetrakis(tetramethylguanidino)phenazin (ttmgph) handelt es sich um einen Vertreter der im Arbeitskreis Himmel entwickelten Ligandenklasse der guanidino-funktionalisierten Aromaten (GFA). Im Gegensatz zu den elektronenreichen Vertretern dieser Ligandenklasse mit kleinem aromatischem Grundgerüst, wie z. B. Benzol, führt die Substitution des elektronenarmen heteroaromatischen Phenazins mit elektronenschiebenden Guanidinogruppen nicht zur Bildung eines redoxaktiven Elektronendonors. Das ermöglicht die Weiterentwicklung sowohl zum Elektronendonor- als auch zum Elektronenakzeptor-Liganden. Das ausgeprägte π-System mit kleiner HOMO-LUMO- Lücke erlaubt es außerdem, Änderungen der Grenzorbitalenergien unter anderem anhand von UV/Vis- Absorptions- und Emissionsspektroskopie zu verfolgen. Die Auswirkung von Umgebungseinflüssen auf ttmgph im Festkörper und in Lösung konnte mittels Matrixisolationstechnik untersucht werden. Dadurch wurde gezeigt, dass die Wechselwirkungen in kondensierten Phasen, im Vergleich zum nahezu isoliert vorliegenden Molekül in der Argon-Matrix, eine Verringerung des HOMO-LUMO-Abstands zur Folge hat. Der Stokes-Shift hingegen wird durch das Lösungsmittel nicht beeinflusst, während er im Festkörper eine Zunahme erfährt. Die differenzierte Lewisbasizität der Phenazin- und Guanidin-Iminstickstoffatome ermöglicht die schrittweise Koordination verschiedener Metalle. So konnten zunächst dinukleare Nickel(II)- und Kupfer(II)-Komplexe, durch Koordination der Guanidinogruppen, erhalten werden. In diesen wurden Elektronendonor-Eigenschaften des Liganden in Form von Ligand-Metall-Charge-Transfer-Übergängen (LMCT) beobachtet, welche mit Hilfe von TD-DFT-Rechnungen identifiziert wurden. Die anschließende Koordination der Phenazin-Stickstoffatome an Kupfer(I)-chlorid führt zu gemischtvalenten bzw. hetero-bimetallischen vierkernigen Komplexen, in denen die zuvor beobachteten LMCT-Übergänge bei trigonaler Kupfer(I)-Koordination ausgeschaltet sind, während sie bei linearer Koordination erhalten bleiben. Durch Benzylierung der Guanidinogruppen hingegen konnte deren elektronenschiebende Wirkung kompensiert und somit die Elektronenakzeptor-Eigenschaften des Phenazingerüsts wiedererlangt werden. Dies wurde anhand von Cyclovoltammetrie (CV) sowie, bei anschließender Kupfer(I)- Koordination der Phenazin-Stickstoffatome, in Form von Metall-Ligand-Charge-Transfer-Übergängen (MLCT) beobachtet. MLCT-Übergänge finden, laut Rechnung, auch bei Koordination der Guanidinogruppen an Kupfer(I)-chlorid statt. Anschließende Methylierung der Phenazin- Stickstoffatome senkt die LUMO-Energie des Liganden ab und ein intramolekularer Elektronentransfer vom Metall zum Liganden, der zur Reduktion des Phenazin-Systems führt, wird induziert. So konnten die Grenzorbitalenergien von ttmgph gezielt beeinflusst und somit sowohl Elektronendonor- als auch Elektronenakzeptor-Eigenschaften hervorgerufen werden, wodurch die Ligandenklasse der GFA, die bisher vor allem Elektronendonoren umfasste, um die Elektronenakzeptor-Eigenschaft ergänzt wird

A Recurrent Case of Targetoid Hemosiderotic Hemangioma: A Case Report and a Comprehensive Review of the Literature

Targetoid hemosiderotic hemangioma is an acquired vascular malformation of unknown origin. We report the case of a 31-year-old man with a recurrent and spontaneous regressive targetoid hemosiderotic hemangioma. Diagnosis relied on clinical and histological findings. Physical examination revealed presence of an approximately 2 cm targetoid lesion located on the left arm, and associated with pain after pressure. No trigger agent (trauma, insect sting) was reported. Dermoscopy showed a group of red lacunae centrally, encircled by an intermediate yellow circular homogenous area and a red violaceous homogenous ring in the periphery. The histopathological examination and the immunohistochemical staining of the lesion were characteristic for a hemangioma-like proliferation of vessels in the upper part of the dermis, similar to a targetoid hemosiderotic angioma. We also review epidemiological, clinical, and histopathological findings in 6 similar cases presented in the literature. Spontaneous regression and recurrence have rarely been described in this type of skin lesion

Sex-Based Differences in Bleeding Risk After Percutaneous Coronary Intervention and Implications for the Academic Research Consortium High Bleeding Risk Criteria.

Background Female sex was not included among the high bleeding risk (HBR) criteria by the Academic Research Consortium (ARC) as it remains unclear whether it constitutes an HBR condition after percutaneous coronary intervention. We investigated whether female sex associates with HBR and assessed the performance of ARC HBR criteria separately in women and men. Methods and Results Among all consecutive patients undergoing percutaneous coronary intervention between 2009 and 2018, bleeding occurrences up to 1 year were prospectively collected and centrally adjudicated. All but one of the originally defined ARC HBR criteria were assessed, and the ARC HBR score generated accordingly. Among 16 821 patients, 25.6% were women. Compared with men, women were older and had lower creatinine clearance and hemoglobin values. After adjustment, female sex was independently associated with access-site (adjusted hazard ratio, 2.14; 95% CI, 1.22-3.74; P=0.008) but not with overall or non-access-site 1-year Bleeding Academic Research Consortium 3 or 5 bleeding. This association remained consistent when the femoral but not the radial approach was chosen. The ARC HBR score discrimination, using the original criteria, was lower among women than men (c-index 0.644 versus 0.688; P=0.048), whereas a revised ARC HBR score, in which age, creatinine clearance, and hemoglobin were modeled as continuous rather than dichotomized variables, performed similarly in both sexes. Conclusions Female sex is an independent predictor for access-site bleeding but not for overall bleeding events at 1 year after percutaneous coronary intervention. The ARC HBR framework shows an overall good performance in both sexes, yet is lower in women than men, attributable to dichotomization of age, creatinine clearance, and hemoglobin values, which are differently distributed between sexes. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02241291

Efficient n‑Doping and Hole Blocking in Single-Walled Carbon Nanotube Transistors with 1,2,4,5‑Tetrakis(tetramethylguanidino)ben-zene

Efficient, stable, and solution-based n-doping of semiconducting single-walled carbon nanotubes (SWCNTs) is highly desired for complementary circuits but remains a significant challenge. Here, we present 1,2,4,5-tetrakis­(tetramethylguanidino)­benzene (ttmgb) as a strong two-electron donor that enables the fabrication of purely n-type SWCNT field-effect transistors (FETs). We apply ttmgb to networks of monochiral, semiconducting (6,5) SWCNTs that show intrinsic ambipolar behavior in bottom-contact/top-gate FETs and obtain unipolar n-type transport with 3–5-fold enhancement of electron mobilities (approximately 10 cm² V^–1 s^–1), while completely suppressing hole currents, even at high drain voltages. These n-type FETs show excellent on/off current ratios of up to 10⁸, steep subthreshold swings (80–100 mV/dec), and almost no hysteresis. Their excellent device characteristics stem from the reduction of the work function of the gold electrodes <i>via</i> contact doping, blocking of hole injection by ttmgb²⁺ on the electrode surface, and removal of residual water from the SWCNT network by ttmgb protonation. The ttmgb-treated SWCNT FETs also display excellent environmental stability under bias stress in ambient conditions. Complementary inverters based on n- and p-doped SWCNT FETs exhibit rail-to-rail operation with high gain and low power dissipation. The simple and stable ttmgb molecule thus serves as an example for the larger class of guanidino-functionalized aromatic compounds as promising electron donors for high-performance thin film electronics

Intelligence Artificielle et système d'identification sur le territoire du Rhin supérieur

Efficient identity management is not only a concern of the virtual world but also paramount for modern open societies like the European Union. Non-intrusive, AI-based techniques of continuous authentication have recently been proposed to increase the security, efficiency and user friendliness of online systems and services. We introduce the research project aura.ai that will investigate how to transfer and apply these novel means of AI-based authentication in the public transportation area of the Upper-Rhine region

Intelligence Artificielle et système d'identification sur le territoire du Rhin supérieur

Efficient identity management is not only a concern of the virtual world but also paramount for modern open societies like the European Union. Non-intrusive, AI-based techniques of continuous authentication have recently been proposed to increase the security, efficiency and user friendliness of online systems and services. We introduce the research project aura.ai that will investigate how to transfer and apply these novel means of AI-based authentication in the public transportation area of the Upper-Rhine region

Impact of clinical presentation on bleeding risk after percutaneous coronary intervention and implications for the ARC-HBR definition.

BACKGROUND The identification of bleeding risk factors in patients undergoing percutaneous coronary intervention (PCI) is essential to inform subsequent management. Whether clinical presentation per se affects bleeding risk after PCI remains unclear. AIMS We aimed to assess whether clinical presentation per se predisposes to bleeding in patients undergoing PCI and if the Academic Research Consortium (ARC) High Bleeding Risk (HBR) criteria perform consistently in acute (ACS) and chronic (CCS) coronary syndrome patients. METHODS Consecutive patients undergoing PCI from the Bern PCI Registry were stratified by clinical presentation. Bleeding events at one year were compared in ACS versus CCS patients, and the originally defined ARC-HBR criteria were assessed. RESULTS Among 16,821 patients, 9,503 (56.5%) presented with ACS. At one year, BARC 3 or 5 bleeding occurred in 4.97% and 3.60% of patients with ACS and CCS, respectively. After adjustment, ACS remained associated with higher BARC 3 or 5 bleeding risk (adjusted HR 1.21, 95% CI: 1.01-1.43; p=0.034), owing to non-access site-related occurrences, which accrued mainly within the first 30 days after PCI. The ARC-HBR score had lower discrimination among ACS compared with CCS patients, and its performance slightly improved when ACS was computed as a minor criterion. CONCLUSIONS ACS presentation per se predicts one-year major bleeding risk after PCI. The ARC-HBR score discrimination appeared lower in ACS than CCS, and its overall performance improved numerically when ACS was computed as an additional minor risk criterion