Zinkkomplexe mit neutralen N-Donorliganden als Katalysatoren der Ringöffnungspolymerisation von Lactid

Polylactide is a biobased and biodegradable plastic which, due to its favourable material properties, posseses the potential to compete against petrochemical-based plastics in many fields of application. Catalysts that are suitable for the production of polylactide under industrial conditions are rare. In the present work zinc complexes with neutral N-donor ligands that combine the necessary robustness towards air and moisture with high polymerisa-tion catalysis are used. By means of the class of guanidine quinoline hybrid ligands the ligand’s basicity was examined, because this feature plays a significant role in the polymerization catalysis. Using experimental and density functional theoretical studies the polymerization mechanism with this catalyst class could be elucidated. The polymerization proceeds via a coordination-insertion mechanism during which the neutral but highly nucleophilic guanidine function induces the ring-opening of the lactide. The influence of the catalyst structure on the stereoselectivity in lactide polymerization was studied by density functional theoretical, mechanistical calculations using the example of aluminium-based complexes and by experimental polymerization studies using the example of tin-based catalysts, with the result, that a high steric demand at suitable positions of the ligand could lead to a high influence on the stereoselectivity. With the objective of increasing the stereoselectivity of the guanidine quinoline catalysts, the ligands were modified by introduction of sterically demanding substituents. The resulting zinc complexes show activity in the lactide polymerization and with bis(chelate)-complexes an enrichment of heterotactic enchainments could be observed in the resulting polymer. Also zinc complexes with further guanidine ligands and other classes of neutral N-donor ligands (oxalic amidines, diamines and triazapentadienes) were successfully applied as catalysts of the lactide polymerization. Thus, the concept of obtaining robust and catalytically active zinc complexes could be confirmed for several classes of neutral N-donor ligands.Polylactid ist ein biobasierter und biologisch abbaubarer Kunststoff, der aufgrund seiner hervorragenden Materialeigenschaften das Potenzial besitzt, auf fossilen Ressourcen basierende Kunststoffe in vielen Anwendungsbereichen zu ersetzen. Katalysatoren, die auch für die Herstellung von Polylactid unter industriellen Bedingungen geeignet sind, sind rar. In der vorliegenden Arbeit werden Zinkkomplexe mit neutralen N-Donorliganden in der Lactidpolymerisation eingesetzt, die die notwendige Robustheit gegenüber Luft und Feuchtig-keit aufweisen und gleichzeitig aktive Katalysatoren darstellen. Anhand der Klasse der Guanidin-Chinolin-Hybridliganden wurde die Basizität der Liganden untersucht, da diese bei der Polymerisationskatalyse eine entscheidende Rolle spielt. Durch experimentelle und dichtefunktionaltheoretische Studien konnte der Polymerisationsmechanismus mit dieser Katalysatorklasse aufgeklärt werden. Die Polymerisation verläuft über einen Koordinations-Insertions-Mechanismus, bei dem die neutrale aber stark nukleophile Guanidinfunktion die Ringöffnung des Lactids induziert. Der Einfluss der Katalysatorstruktur auf die Stereoselektivität in der Lactidpolymerisation wurde durch dichtefunktionaltheoretische, mechanistische Berechnungen am Beispiel von aluminiumbasierten Komplexen und durch experimentelle Polymerisationsstudien anhand von zinnbasierten Katalysatoren untersucht, mit dem Ergebnis, dass ein hoher sterischer Anspruch an geeigneten Positionen der Liganden einen hohen Einfluss auf die Stereoselektivität aufweisen kann. Mit dem Ziel, die Stereoselektivität der Guanidin-Chinolin-Katalysatoren zu erhöhen, wurden die Liganden durch die Einführung sterisch anspruchsvoller Substituenten modifiziert. Die resultierenden Zinkkomplexe zeigen Aktivität in der Lactidpolymerisation und bei Bis(chelat)-Komplexen konnte eine Anreicherung von heterotaktischen Sequenzen in den Polymeren beobachtet werden. Auch Zinkkomplexe mit weiteren Guanidinliganden und anderen Klassen neutraler N-Donorliganden (Oxalamidine, Diamine und Triazapentadiene) wurden erfolgreich als Ka-talysatoren der Lactidpolymerisation eingesetzt. Dadurch konnte das Konzept, mit neutralen Liganden robuste und katalytisch aktive Zinkkomplexe zu erhalten, für mehrere N-Donor-Ligandenklassen bestätigt werden

New Guanidine-Pyridine Copper Complexes and Their Application in ATRP

The guanidine hybrid ligands, (tetramethylguanidine)methylenepyridine (TMGpy) and (dimethylethyleneguanidine)methylenepyridine (DMEGpy), were proven to be able to stabilize copper complexes active in the solvent-free polymerization of styrene at 110 degrees C using 1-phenylethylbromide as the initiator. The polymerization proceeded after first-order kinetics, and polystyrenes with polydispersities around 1.2 could be obtained. Using the ligand, DMEGpy, three new copper guanidine-pyridine complexes could be synthesized and structurally characterized. Their structural characteristics are discussed

New Guanidine-Pyridine Copper Complexes and Their Application in ATRP

The guanidine hybrid ligands, (tetramethylguanidine)methylenepyridine (TMGpy) and (dimethylethyleneguanidine)methylenepyridine (DMEGpy), were proven to be able to stabilize copper complexes active in the solvent-free polymerization of styrene at 110 degrees C using 1-phenylethylbromide as the initiator. The polymerization proceeded after first-order kinetics, and polystyrenes with polydispersities around 1.2 could be obtained. Using the ligand, DMEGpy, three new copper guanidine-pyridine complexes could be synthesized and structurally characterized. Their structural characteristics are discussed

PERFIL PROTEICO DO LÍQUIDO FOLICULAR COLETADO DE OVÁRIOS EM DIFERENTES FASES DO CICLO ESTRAL DE BOVINOS.

O microambiente do gameta feminino é o líquido folicular e, portanto as proteínas presentes no líquido folicular devem interferir na qualidade do oócito. Com o objetivo de verificar o perfil proteico do líquido folicular de folículos de diferentes fases do ciclo estral de bovinos este experimento foi delineado. Para tanto, os líquidos foliculares provenientes de ovários de vacas de abatedouro foram alocados em 5 diferentes fases do ciclo estral, levando em conta a presença ou ausência do corpo lúteo (CL) e sua caracterização morfológica. “Pools” de líquido folicular foram coletados de folículos de 2 a 7 mm de ovários em 5 diferentes fases do ciclo estral (1=CL inicial, hemorrágico; 2=CL em desenvolvimento; 3=CL maduro; 4=CL em regressão e 5=ausência de CL). O perfil proteico foi avaliado por eletroforese em gel de poliacrilamida e determinado em porcentagens nas amostras de cada fase. Os polipeptídeos de 35, 32, 30 e 18 KDa variam consideravelmente nas amostras de diferentes fases do ciclo estral. O polipeptídeo de mesmo peso molecular que o IGFBP-2 está mais presente nas amostras de líquido folicular ao final do ciclo estral. Maior número de polipeptídeos é observado em folículos antrais pequenos de ovários em que o CL está em regressão

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030