Design, Syntheses, and Magnetic Properties of Dy(Ⅲ)-based Single-Molecule Magnets and Isotopologues

Einzelmolekülmagnete (SMMs, single molecule magnets) haben ein großes Spektrum an potenziellen Einsatzgebieten in z.B. molekularer Spintronik, Datenspeichern mit hoher Aufzeichnungsdichte oder in Quantencomputern. Aufgrund der starken Spin-Bahn Kopplung und dem daraus resultierenden stark anisotropen 6H15/2 Grundzustand, sind Dy(III) Ionen die derzeit vielversprechendste Basis für SMMs. Diese Thesis behandelt Dy(III)-Einzelmolekülmagnete auf Basis von unterschiedlichen β-Diketonat- sowie zusätzlichen Hilfsliganden. Die Arbeit ist in folgende drei Abschnitte unterteilt: 1. Kapitel 2: Es wurden sechs mononukleare Dy(III) Komplexe, basierend auf vier verschiedenen β-Diketonatliganden (tmdh, BTFA, NTFA, hfac) und zwei Hilfsliganden (POPh3, 2,5-tpy), synthetisiert. Die gefundenen Komplexe sind [Dy(tmhd)3(POPh3)] (2-1), [Dy(tmhd)3(2,5-tpy)] (2-2), [Dy(BTFA)3(2,5-tpy)] (2-3), [Dy(NTFA)3(2,5-tpy)] (2-4), [Dy(NTFA)3(2,5-tpy)·C2H5OH] (2-5) und [Dy(hfac)3(2,5-tpy)(H2O)·(2,5-tpy)] (2-6). Das Dy(III) Ion in Komplex 2-1 befindet sich in einer N2O6 Koordinationsumgebung, die am besten als überkapptes Oktaeder mit C3v Symmetrie beschrieben wird. In den Komplexen 2-2, 2-3, 2-4 und 2-5 befindet sich das Dy(III) Ion ebenfalls in einer N2O6 Umgebung, allerdings besser beschrieben als quadratisches Antiprisma mit D4d Symmetrie. Die Koordinationsgeometrie in Komplex 2-6 ist ein kugelförmiges quadratisches Antiprisma mit C2v Symmetrie, bei der sich das Dy(III) in einer N2O7 Umgebung befindet. Magnetische Untersuchungen haben gezeigt, dass alle dieser Komplexe SMMs sind. Die Energiebarrieren (Ueff) wurden bestimmt mit 35,5 K (2-1, Hdc = 1200 Oe), 36,7 K (2-2, Hdc = 800 Oe), 16,6 K (2-3, Hdc = 0 Oe), 75,5 K (2-4, Hdc = 0 Oe), 63,9 K (2-5, Hdc = 0 Oe) und 5,3 K (2-6, Hdc = 800 Oe). Die jeweiligen Relaxationseigenschaften ergeben sich durch die veränderte Koordinationsumgebung der Dy(III) Ionen. Diese Arbeit zeigt, wie die SMM Eigenschaften, durch Änderungen der Substituenten der β-Diketonatliganden und der sich dadurch ändernden Koordinationsumgebung, beeinflusst werden können. 2. Kapitel 3: Unter Verwendung von isotopisch angereichertem 163Dy und 164Dy, sowie mit kommerziell erhältlichem Dy wurden sieben dinukleare Dy(III) Komplexe erfolgreich synthetisiert. Basierend auf drei unterschiedlichen Brückenliganden, 2,2‘:5‘,5‘‘:2‘‘,2‘‘‘-Quarterpyridin (bisbpy), 1,6,7,12-Tetraazaperylen (TAPE) und 3,6-bis(2-pyridyl)-1,2,4,5-tetrazin (bptz), sowie drei verschiedenen β-Diketonatliganden, tmhd, BTFA und NFTA, wurden verschiedene Komplexe erhalten. Bei der Verwendung des bptz Liganden beobachtet wir eine unerwartete Ringöffnungsreaktion zu dem neuen Liganden N\u27-[(E)-pyrazin-2-yl)methylidene]pyrazine-2-carbohydrazonate (PHZP). Die erhaltenen Komplexe sind: [(Dy(tmhd)3)2(bisbpy)·CH2Cl2] (3-1), [163Dy2(tmhd)6(tape)] (3-2), [164Dy2(tmhd)6(tape)] (3-3), [Dy2(BTFA)6(tape)] (3-4), [Dy2(NTFA)6(tape)] (3-5), [(163Dy(BTFA)2)2(PHZP)2] (3-6) und [(164Dy(BTFA)2)2(PHZP)2] (3-7). In den Komplexen 3-1, 3-2, 3-3, 3-4 und 3-5 befinden sich die Dy(III) jeweils in einer N2O6 Umgebung mit D4d Symmetrie, für die Verbindungen 3-1 und 3-4, und mit D2d Symmetrie in 3-2, 3-3 und 3-5. In den Komplexen 3-6 und 3-7 befinden sich die Dy1-Positionen in einer kugelförmig dreifach überkappten trigonalen Prisma D3h-Symmetrie. Die Dy2-Positionen werden besser beschrieben durch eine Muffin Struktur mit Cs-Symmetrie. Alle diese Komplexe sind SMMs ohne angelegtes externes Magnetfeld mit Ueff Werten von 30,8 K (3-1), 80,6 K (3-2), 73,3 K (3-3), 47,0 K (3-4), 24,5 K (3-5), 50,7 K (3-6) und 57,1 K (3-7). Vergleicht man die Komplexe 3-2 bis 3-5, zeigt 3-5 die niedrigste Energiebarriere, aufgrund der elektronenschiebenden Gruppen am β-Diketonat. Das beweist, dass der Austausch der Substituenten am β-Diketonat eine Möglichkeit darstellt, die magnetischen Eigenschaften dinuklearer Dy(III) Komplexe abzustimmen. Die Ergebnisse von µ-SQUID Messungen an 3-2(I = 5/2), 3-3(I = 0), 3-6(I = 5/2) und 3-7(I = 0), bei tiefen Temperaturen, zeigen das der Kernspin eine entscheidende Rolle für den Relaxationsprozess spielt und die Dy-Dy Entfernungen die Intensität der intramolekularen Austauschwechselwirkungen beeinflussen. 3. Kaptiel 4: Zwei trinukleare Dy(III) Komplexe – [Dy3(tmhd)9(TBB)] (4-1) und [Dy3(tmhd)9(TBPB)·CH2Cl2] (4-2) – basierend auf den beiden Brückenliganden 1,3,5-tri(2,2‘-bipyridin-5-yl)benzol (TBB) und 1,3,5-tris{[2,2‘-bipyridin-5-ylenthynyl]phenyl}benzol (TBPB) sowie dem β-Diketonat tmhd, wurden erfolgreich synthetisiert. In beiden Komplexen befinden sich die Dy(III) Ionen in einer quadratisch antiprismatischen N2O6 Koordinationsumgebung mit D4d Symmetrie. Die Komplexe zeigen SMM Verhalten im Nullfeld mit Ueff = 75,6 K (4-1) und 92,5 K (4-2), bestimmt durch AC Suszeptibilitätsmessungen. Die Unterschiede der beiden N-Donorliganden bewirken geringe Veränderungen in der Mikroumgebung und führen dadurch zu unterschiedlichem magnetischem Verhalten

Preparation and Characterization of PMMA and its Derivative via RAFT Technique in the Presence of Disulfide as a Source of Chain Transfer Agent

Poly(methyl methacrylate) (PMMA) were synthesized by using chain transfer agents(CTA), S-1-Dodecyl-S′-(α,α′-dimethyl-α-acetic acid) trithiocarbonate (MTTCD), S,S′-bis (2-hydroxyethyl-2′-dimethylacrylate) trithiocarbonate (BDATC), 2-cyanoprop-2-yl dithiobenzoate (CPDB) respectively, through the reversible addition fragmentation chain transfer (RAFT) polymerization under a range of synthesis conditions. The results indicated that the structure of the end-group of RAFT agents had significant effects on the ability to control polymerization. Compared with MTTCD and CPDB, BDATC can provide better control over the relative molecular mass, distribution and polymerization of PMMA. The derived well-controlled block copolymer PMMA-b-PDMAEMA and PMMA-b-PDMAEA were also successfully prepared by using N, N-dimethylaminoethy acrylate (DMAEA) or N, N-dimethylaminoethyl methacrylate (DMAEMA) as the second monomer. The chemical composition and structure of the products were characterized by FTIR, 1HNMR, XRD and DSC. CO2 and N2 permeation performance of the PMMA-b-PDMAEA/PS composite membranes were tested at different pressure. The results showed that the resulted composited membrane had a CO2 permeation rate of 3.68×10-5cm3 (STP) cm-2s-1cmHg-1, a N2 permeation rate of 1.78×10-7 cm3 (STP) cm-2s-1cmHg-1 and an ideal CO2/ N2 selectivity of 206.6 at a feed gas pressure of 7.6 cmHg and 30 oC

Observational Studies on the Association Between Post-diagnostic Metformin Use and Survival in Ovarian Cancer: A Systematic Review and Meta-Analysis

Objectives: To summarize and quantify the relationship between post-diagnostic metformin use and ovarian cancer (OC) survival.Methods: We systematically conducted an updated meta-analysis based on observational studies published up to December 31, 2018, identified from PubMed and Web of Science. Two team members independently extracted data and assessed the quality of each study. Summary Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using a random-effects model.Results: Five cohort studies including 3,582 OC patients were included. All studies were graded as low risk of bias according to the Newcastle-Ottawa quality assessment scale. Post-diagnostic metformin use was associated with improved overall survival (summarized HR = 0.42, 95% CI = 0.31–0.56; I2 = 0%, P = 0.842) and progression-free survival (summarized HR = 0.69, 95% CI = 0.45–1.07; I2 = 61.9%, P = 0.049) of OC patients. For OC patients with diabetes, post-diagnostic metformin use was associated with improved overall survival (summarized HR = 0.51, 95% CI = 0.28–0.95; I2 = 47.6%, P = 0.149) and progression-free survival (summarized HR = 0.38, 95% CI = 0.27–0.55; I2 = 0%, P = 0.594). No significant publication bias was detected in these analyses.Conclusions: Post-diagnostic metformin use is consistently associated with better survival of OC patients regardless of diabetes status. Studies with larger sample sizes and prospective designs are required to confirm these findings and obtain detailed information, including standardized references for comparison, intensity and dose of metformin use, and further adjustment for potential confounders

Building and analyzing protein interactome networks by cross-species comparisons

<p>Abstract</p> <p>Background</p> <p>A genomic catalogue of protein-protein interactions is a rich source of information, particularly for exploring the relationships between proteins. Numerous systems-wide and small-scale experiments have been conducted to identify interactions; however, our knowledge of all interactions for any one species is incomplete, and alternative means to expand these network maps is needed. We therefore took a comparative biology approach to predict protein-protein interactions across five species (human, mouse, fly, worm, and yeast) and developed InterologFinder for research biologists to easily navigate this data. We also developed a confidence score for interactions based on available experimental evidence and conservation across species.</p> <p>Results</p> <p>The connectivity of the resultant networks was determined to have scale-free distribution, small-world properties, and increased local modularity, indicating that the added interactions do not disrupt our current understanding of protein network structures. We show examples of how these improved interactomes can be used to analyze a genome-scale dataset (RNAi screen) and to assign new function to proteins. Predicted interactions within this dataset were tested by co-immunoprecipitation, resulting in a high rate of validation, suggesting the high quality of networks produced.</p> <p>Conclusions</p> <p>Protein-protein interactions were predicted in five species, based on orthology. An InteroScore, a score accounting for homology, number of orthologues with evidence of interactions, and number of unique observations of interactions, is given to each known and predicted interaction. Our website <url>http://www.interologfinder.org</url> provides research biologists intuitive access to this data.</p

Behavior of Protein-Inspired Synthetic Random Heteropolymers

Random heteropolymers (RHPs) are an interesting class of materials useful in many theories and applications. While previous studies typically focused on simplified RHP systems, here we explore a more complex scenario inspired by highly heterogeneous molecules like proteins. Our system consists of four monomers mimicking different classes of amino acids. Using Molecular Dynamics simulations and Small-Angle X-Ray Scattering, we explore dynamical and structural features of these RHPs in solution. Our results show the RHPs assemble with heterogeneous interfaces reminiscent of protein surfaces. The polymer backbones appear frozen at room temperature on the nano- to micro-second timescale with molten globule morphology, albeit their conformational space has multiple metastable conformations for a given sequence, drawing comparison to Intrinsically Disordered Proteins. Local connectivity and chemistry are also shown to have substantial impact on polymer solvation. The work presented here indicates that RHPs share similarities with proteins to be leveraged in bio-mimetic and bio-inspired applications

Stimulatory Effect of 5-Hydroxytryptamine (5-HT) on Rat Capsaicin-Sensitive Lung Vagal Sensory Neurons via Activation of 5-HT\u3csub\u3e3\u3c/sub\u3e Receptors

5-hydroxytryptamine (5-HT) is an inflammatory mediator known to be released in lung. Capsaicin-sensitive lung vagal (CSLV) afferents function as a primary sensor for detecting chemical stimuli and produce consequent reflexes during lung inflammation. To characterize the effect of 5-HT on CSLV afferents, responses of cardiorespiratory reflexes and single-unit C-fiber afferents to right-atrial injections of 5-HT were investigated in anesthetized Sprague-Dawley rats. Bolus injection of 5-HT (8 μg/kg) caused an immediate augmented breath and apnea, accompanied by hypotension and bradycardia. These initial responses were then followed by a brief pressor response and a more sustained depressor response. After a perineural treatment of both cervical vagi with capsaicin to block the conduction of C fibers, 5-HT still triggered the augmented breath, but no longer evoked the apnea, bradycardia and hypotension, indicating an involvement of C-fiber activation. The remaining augmented breath induced by 5-HT after perineural capsaicin treatment was totally eliminated by vagotomy. To further study the effect of 5-HT on CSLV afferents, activities arising from these afferents were determined using the single-fiber recording technique. Right-atrial injection of 5-HT evoked an intense discharge in CSLV afferents in a dose-dependent manner. The highest dose of 5-HT (16 μg/kg) activated 79% (19/24) of CSLV afferents which were also sensitive to capsaicin (0.8 μg/kg). The pretreatment of tropisetron, a selective antagonist of the 5-HT3 receptor, completely blocked CSLV-afferents stimulation induced by 5-HT but did not affect that by capsaicin. Furthermore, a similar afferent response of CSLV afferents was mimicked by phenylbiguanide, a selective agonist of the 5-HT3 receptor. In isolated rat lung vagal C neurons, 5-HT induced intense calcium transients in a dose-dependent manner. The highest concentration (3 μM) of 5-HT activated 67% (18/27) of the CSLV neurons. The 5-HT-induced response was totally abolished by pretreatment of tropisetron. In conclusion, 5-HT exerts an intense stimulatory effect on lung C-fiber terminals mediated through an activation of the 5-HT3 receptor, which may contribute to the airway hypersensitivity under lung inflammation

It\u27s not just the size that matters: crystal engineering of lanthanide-based coordination polymers

Synthesis and characterization of Lewis base free coordination polymers of selected lanthanides are presented. For this purpose, the substituted Cot$^{TIPS}$ ligand (Cot$^{TIPS}$ = 1,4-bis-triisopropylsilyl-cyclo-octatetraendiide) was used to synthesize homoleptic, anionic multidecker compounds of the type [K{Ln$^{III}$(ɳ$^8$-Cot$^{TIPS}$)$_2$}]$_n$. Depending on the solvent used for crystallization and the ionic radii of the lanthanide cations, three different categories of one-dimensional heterobimetallic coordination polymers were obtained in the solid state. For the early lanthanides La and Ce a unique helical conformation was obtained by crystallization from toluene, while the ionic radius of Pr seems to be a turning point towards the crystallization of zigzag polymers. For Er a third structural motif, a trapezoidal wave polymer was observed. Additionally, the zigzag polymer for all compounds could be obtained by changing the solvent from toluene to Et$_2$O, reavealing a correlation between solid-state structure and ionic radii as well as solvent. While photoluminescence (PL) properties of Cot-lanthanide compounds are scarce, the La complexes show ligand centered green luminescence, whereas the Ce complexes reveal deep red emission origin from d–f transitions. The Er-compounds are single-molecule magnets, in which the magnetic relaxation of each Er ion occurs isolated from its neighbors at temperatures above 10 K, while below 9 K a strong antiferromagnetic coupling between the Er ions was seen