Eldorado - Repositorium der TU Dortmund

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Aktuellste Veröffentlichungen

Insights into the mechanochemical glass formation of zeolitic imidazolate frameworks
(Deutsches Elektronen-Synchrotron, DESY, Hamburg, 2024-06-14) Xue, Wen-Long; Das, Chinmoy; Weiß, Jan-Benedikt; Henke, Sebastian
Metal–organic framework (MOF) glasses, known for their potential in gas separation, optics, and solid-state electrolytes, benefit from the processability of their (supercooled) liquid state. Traditionally, MOF glasses are produced by heating MOF crystals to their melting point and then cooling the liquid MOF to room temperature under an inert atmosphere. While effective, this melt-quenching technique requires high energy due to the high temperatures involved. It also limits the scope of new material development by restricting the compositional range to only those combinations of metal ions and linkers that are highly thermally stable. An alternative, mechanical milling at room temperature, has demonstrated its capability to transform MOF crystals into amorphous phases. However, the specific conditions under which these amorphous phases exhibit glass-like behavior remain uncharted. In this study, we explore the mechanochemical amorphization and vitrification of a variety of zeolitic imidazolate frameworks (ZIFs) with diverse linkers and different metal ions (Zn2+, Co2+ and Cu2+) at room temperature. Our findings demonstrate that ZIFs capable of melting can be successfully converted into glasses through ball-milling. Remarkably, some non-meltable ZIFs can also be vitrified using the ball-milling technique, as highlighted by the preparation of the first Cu2+-based ZIF glass.
Ligand conformation controls assembly of a helicate/mesocate, heteroleptic [Pd2L2L’2] cages and a six‐jagged [Pd6L12] ring
(Wiley, 2024-06-10) Benchimol, Elie; Ebbert, Kristina E.; Walther, Alexandre; Holstein, Julian J.; Clever, Guido H.
Molecular building blocks, capable of adopting several strongly deviating conformations, are of particular interest in the development of stimuli-responsive self-assemblies. The pronounced structural flexibility of a short acridone-based bridging ligand, equipped with two monodentate isoquinoline donors, is herein exploited to assemble a surprisingly diverse series of coordination-driven Pd(II) architectures. First, it can form a highly twisted Pd2L4 helicate, transformable into the corresponding mesocate, controlled by temperature, counter anion and choice of solvent. Second, it also allows the formation of heteroleptic cages, either from a mix of ligands with Pd(II) cations or by cage-to-cage transformation from homoleptic assemblies. Here, the acridone-based ligand tolerates counter ligands that carry their donors either in a diverging or converging arrangement, as it can rotate its own coordination sites by 90° and structurally adapt to both situations via shape complementarity. Third, by a near 180° rotation of only one of its arms, the ligand can adopt an S-shape conformation and form an unprecedented C6h-symmetric Pd6L12 saw-toothed six-membered ring.
Intramolecularly O,N,O‐coordinated tin(II) salts: syntheses, structures, cyclization, and transition metal complexation
(Wiley, 2024-06-04) Alnasr, Hazem; Mroß, David; Platzek, André; Nayyar, Bastian; Řičica, Tomáš; Schollmeyer, Dieter; Jambor, Roman; Hoffmann, Alexander; Jurkschat, Klaus
We report the syntheses of tin(II) salts of the types [L1SnX]SnX3 [L1=2,6-{(i-PrO)2(O)P}2C5H3N: 1, X=Cl; 2, X=Br], [L2SnCl]SnCl3 [L2=2-{(i-PrO)Ph(O)P}-6-{(i-PrO)2(O)P}C5H3N: 3], [L3SnX]SnX3 [L3=2,6-{MeO(O)C}2C5H3N: 4, X=Cl; 5, X=Br], [L4SnX]SnX3 [L4=2,6-{Et2N(O)C}2C5H3N: 6, X=Cl; 7, X=Br]. These compounds were obtained by addition of SnX2 to the corresponding ligand inducing autoionization of the respective tin(II) halide. The thermal stability of 1, 3, and 4 was elucidated, giving, under ester cleavage and cyclisation, the tin(II) derivatives 8–12. The reaction of [L1SnCl]SnCl3 (1) with W(CO)4(thf)2 afforded the tungsten tetracarbonyl complex [{L1SnCl}{SnCl3}W(CO)4] (13), representing the first example in which a tin(II) stannate anion and a tin(II) stannylium cation simultaneously coordinate to a transition metal centre. The compounds were characterized by single crystal X-ray diffraction analyses and in part by elemental analyses, IR and NMR spectroscopy, electrospray ionization mass spectrometry. DFT calculations accompany the experimental work.
Influence of carbon dioxide on the phase behavior of pharmaceutical drug‐polymer dispersions
(Wiley, 2024-11-29) Klueppelberg, Jana; Handge, Ulrich A.; Thommes, Markus; Winck, Judith
The formulation as amorphous solid dispersion (ASD) addresses recent challenges in the oral administration of poorly-soluble drugs by embedding them in highly-soluble carrier polymers. In this context, utilizing CO2 as a processing agent is an innovative strategy to facilitate the dissolution of the drug in the polymer at comparatively low temperatures without the use of any organic solvents. Within this study, the influence of CO2 on the phase behavior of ASD formulations is investigated. Therefore, high-pressure differential scanning calorimetry is applied to evaluate the dissolution of the drugs in the polymers and the glass transition temperatures under CO2 of four formulations containing the drugs acetaminophen and itraconazole as well as the polymers Soluplus and vinylpyrrolidone/vinyl acetate copolymer. The glass transition temperatures of the ASD formulations decrease with CO2 fraction dissolved in the polymer. The extent of Tg reduction is related to the spatial structure and intermolecular interactions of the polymers. Furthermore, the sorption of CO2 accelerates the diffusion of the drugs in the plasticized polymers. However, phase separation is observed in some formulations under CO2 loading which has an impact on the stability of the ASD and has to be considered in process design.
Modulating polymerase activity through light‐oxygen‐voltage domain insertion
(Wiley, 2024-09-04) Hafki, Daniel; Alda, Jonas; Pietrus, Daniel; Brakmann, Susanne
Biochemical reaction networks adapt to environmental conditions by sensing chemical or physical stimuli and using tightly controlled mechanisms. While most signals come from molecules, many cells can also sense and respond to light. Among the biomolecular structures that enable light sensing, we selected a light-oxygen-voltage (LOV) domain in a previous study that tested the engineering of novel regulatory mechanisms into a nucleic acid polymerase. In this follow-up study, we studied the activities of previously selected variants in kinetic detail, and we generated additional LOV-polymerase fusion variants based on further insertion criteria. Our results provide mechanistic insights into how LOV domain insertion influences polymerase activity in a light-responsive manner: All active and photoresponsive enzyme variants studied by us to date were partially inhibited (i. e., “turned off”) after irradiation with blue light at 470 nm, which can be explained by specific obstructions of the polymerase entry or exit structures (substrate entry channels or product exit channels, or both). Although the effects observed are moderate, we anticipate further engineering strategies that could be used to improve the extent of switchability and possibly to develop a “turn-on mode” insertion.