Publications

CCDC 1411720: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1520086: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A Cholesterol Containing pH‐Sensitive Bistable [2]Rotaxane

Abstract A non‐symmetrical pH‐sensitive bistable [2]rotaxane that bears a cholesterol unit and a tetraphenylmethane group as stopper groups was designed and synthesized in 18 steps. The successful formation of the rotaxane was proven by NMR spectroscopy and MS/MS. Besides a permanent cationic alkylated triazolium unit, the axle contains a secondary amine that can act as a second pH‐sensitive binding site for a crown ether. Depending on the protonation state of this amine function, the crown ether reversibly changes its position by moving between the two binding sites along the axle, as revealed by NMR spectroscopy.

CCDC 836995: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Dinosaur origin of egg color: oviraptors laid blue-green eggs

Protoporphyrin (PP) and biliverdin (BV) give rise to the enormous diversity in avian egg coloration. Egg color serves several ecological purposes, including post-mating signaling and camouflage. Egg camouflage represents a major character of open-nesting birds which accomplish protection of their unhatched offspring against visually oriented predators by cryptic egg coloration. Cryptic coloration evolved to match the predominant shades of color found in the nesting environment. Such a selection pressure for the evolution of colored or cryptic eggs should be present in all open nesting birds and relatives. Many birds are open-nesting, but protect their eggs by continuous brooding, and thus exhibit no or minimal eggshell pigmentation. Their closest extant relatives, crocodiles, protect their eggs by burial and have unpigmented eggs. This phylogenetic pattern led to the assumption that colored eggs evolved within crown birds. The mosaic evolution of supposedly avian traits in non-avian theropod dinosaurs, however, such as the supposed evolution of partially open nesting behavior in oviraptorids, argues against this long-established theory. Using a double-checking liquid chromatography ESI-Q-TOF mass spectrometry routine, we traced the origin of colored eggs to their non-avian dinosaur ancestors by providing the first record of the avian eggshell pigments protoporphyrin and biliverdin in the eggshells of Late Cretaceous oviraptorid dinosaurs. The eggshell parataxon Macroolithus yaotunensis can be assigned to the oviraptor Heyuannia huangi based on exceptionally preserved, late developmental stage embryo remains. The analyzed eggshells are from three Late Cretaceous fluvial deposits ranging from eastern to southernmost China. Reevaluation of these taphonomic settings, and a consideration of patterns in the porosity of completely preserved eggs support an at least partially open nesting behavior for oviraptorosaurs. Such a nest arrangement corresponds with our reconstruction of blue-green eggs for oviraptors. According to the sexual signaling hypothesis, the reconstructed blue-green eggs support the origin of previously hypothesized avian paternal care in oviraptorid dinosaurs. Preserved dinosaur egg color not only pushes the current limits of the vertebrate molecular and associated soft tissue fossil record, but also provides a perspective on the potential application of this unexplored paleontological resource.

CCDC 926029: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Reactivity of self-assembled supramolecular complexes in the gas phase: A supramolecular neighbor group effect

Dynamic Complex‐to‐Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions

Abstract Two new heterobimetallic cages, a trigonal‐bipyramidal and a cubic one, were assembled from the same mononuclear metalloligand by adopting the molecular library approach, using iron(II) and palladium(II) building blocks. The ligand system was designed to readily assemble through subcomponent self‐assembly. It allowed the introduction of steric strain at the iron(II) centres, which stabilizes its paramagnetic high‐spin state. This steric strain was utilized to drive dynamic complex‐to‐complex transformations with both the metalloligand and heterobimetallic cages. Addition of sterically less crowded subcomponents as a chemical stimulus transformed all complexes to their previously reported low‐spin analogues. The metalloligand and bipyramid incorporated the new building block more readily than the cubic cage, probably because the geometric structure of the sterically crowded metalloligand favours the cube formation. Furthermore it was possible to provoke structural transformations upon addition of more favourable chelating ligands, converting the cubic structures into bipyramidal ones.

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

A new 4-hydroxy-L-proline derivative with a charged 1-ethylpyridinium-4-phenoxy substituent has been synthesized with the aim of facilitating mechanistic studies of proline-catalyzed reactions by ESI mass spectrometry. The charged residue ensures a strongly enhanced ESI response compared to neutral unmodified proline. The connection by a rigid linker fixes the position of the charge tag far away from the catalytic center in order to avoid unwanted interactions. The use of a charged catalyst leads to significantly enhanced ESI signal abundances for every catalyst-derived species which are the ones of highest interest present in a reacting solution. The new charged proline catalyst has been tested in the direct asymmetric inverse aldol reaction between aldehydes and diethyl ketomalonate. Two intermediates in accordance with the List–Houk mechanism for enamine catalysis have been detected and characterized by gas-phase fragmentation. In addition, their temporal evolution has been followed using a microreactor continuous-flow technique.

CCDC 1945939: Experimental Crystal Structure Determination

<i>N</i>‐Methylimidazolidin‐4‐one organocatalysts: gas‐phase fragmentations of radical cations by experiment and theory

Electron ionisation mass spectra of N ‐methylimidazolidin‐4‐one organocatalysts were studied by experimental and theoretical means. The molecular ions mostly undergo alpha cleavages of exocyclic substituents that leave the five‐membered ring intact. The type of substituent strongly dominates the appearance of the spectra. Fragmentation cascades are corroborated by metastable ion mass spectra. Quantum Chemistry Electron Ionisation Mass Spectra calculations correlate reasonably well with the experimental electron ionisation spectra and reveal mechanistic details of fragmentation pathways. The drawbacks and benefits of such calculations are discussed. Copyright © 2017 John Wiley &amp; Sons, Ltd.

CCDC 999739: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Sample preparation of Drosophila melanogaster larvae for MALDI imaging

Abstract Mass spectrometry-based lipidomics has emerged as a crucial field for unraveling the complexity of biological systems through comprehensive profiling of lipid species with unparalleled sensitivity and specificity. Among the available techniques, matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI imaging, or MALDI-IMS) stands out as a powerful spatial lipidomics tool, enabling the visualization of distribution and localization of individual lipid classes and species directly within biological tissues. The spatial context of lipids provided by MALDI imaging is especially valuable for studying nutritional and developmental processes in heterogenic tissues. The reliability and quality of MALDI imaging data critically depend on sample preparation, which must preserve both tissue morphology and analyte integrity. Here we introduce a sample preparation protocol for Drosophila melanogaster larval tissue, addressing key limitations of standard protocols such as thin-sectioning. Owing to the small size of Drosophila tissues and the flat morphology of organs such as the fat body, our approach enables direct imaging of the inner organs of the larvae without sectioning. This not only streamlines the workflow and minimizes tissue disruption but also allows simultaneous analysis of all major internal organs in a single measurement. Our approach not only facilitates high-quality MALDI-IMS data acquisition from complex larval tissues but also enables the localization of a broad spectrum of lipid species complementary to data gained by established techniques like liquid chromatography mass spectrometry (LC-MS). These advances position MALDI imaging, when coupled with our optimized preparation workflow, as an indispensable technique for spatially resolved lipidomics studies in small model organisms such as Drosophila larvae. Graphical Abstract

CCDC 966977: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Eine Familie von Heterobimetallischen Würfeln zeigt Spin‐Crossover‐Verhalten nahe Raumtemperatur

Abstract Durch die Verwendung von 4‐(4′‐Pyridyl)anilin als einfachen organischen Baustein in Kombination mit drei verschiedenen Aldehydkomponenten und Metall(II)salzen wurden drei verschiedene Fe 8 Pt 6 ‐Würfel und ihre entsprechenden Zn 8 Pt 6 ‐Analoga mit Hilfe des Subkomponenten Selbstorganisationsansatzes hergestellt. Während die Verwendung von Zink(II)‐Salzen zu diamagnetischen Käfigen führte, ergaben Eisen(II)‐Salze metallosupramolekulare Käfige, die in Lösung Spin‐Crossover‐Verhalten zeigen. Die Spin‐Übergangstemperatur T 1/2 hängt von der verwendeten Aldehydkomponente ab, wodurch sich ein Baukasten für die gezielte Synthese von Spin‐Crossover‐Verbindungen mit maßgeschneiderten Übergangseigenschaften ergibt. Der Einbau von 4‐Thiazolcarbaldehyd oder N ‐Methyl‐2‐Imidazolcarbaldehyd führte zu Käfigen, die bei Raumtemperatur einen Spin‐Crossover durchlaufen, während der mit 1 H ‐4‐Imidazolcarbaldehyd erhaltene Käfig einen Spin‐Übergang bei niedrigen Temperaturen zeigt. Drei der neuen Aggregate wurden durch Synchrotron‐Röntgenbeugung strukturell charakterisiert und alle Strukturen wurden mittels Massenspektrometrie, NMR und UV/Vis‐Spektroskopie untersucht.

CCDC 1919442: Experimental Crystal Structure Determination

Protonation of 2<i>H</i>‐Azaphosphirene Complexes: PN Bond Activation and Ring‐Expansion Reactions

Abstract PN bond activation of 2 H ‐azaphosphirene complexes 1 and 2 by using triflic acid led to ring expansion in the presence of nitriles. In the absence of nitriles, the reaction surprisingly afforded two haptomeric N‐protonated 1‐aza‐3‐phospha‐butadiene complexes in the case of complex 1 , whereas the N‐protonated 2 H ‐azaphosphirene complex [H‐ 2 ] + was characterized by NMR spectroscopy. magnified image Protonation of 2 H ‐azaphosphirene complexes 1 and 2 using trifluoromethanesulfonic acid in the presence and in the absence of nitriles was studied. Reactions with nitrile derivatives of different nucleophilicity and steric demand ( 3 a – f ) led to highly bond‐ and regioselective ring‐expansion reactions of complexes 1 and 2 and yielded 2 H ‐1,4,2‐diazaphosphole complexes 4 a – f and 5 a after deprotonation with NEt 3 . Upon protonation of complex 1 in the absence of nitriles a mixture of two haptomeric N‐protonated 1‐aza‐3‐phosphabuta‐1,3‐diene complexes 13 and 14 was obtained, which upon addition of Me 2 NCN ( 3 a ) and NEt 3 afforded 2 H ‐1,4,2‐diazaphosphole complex 16 a bearing a P‐substituent with only one SiMe 3 group. Protonation of complex 2 led to the 2 H ‐azaphosphirenium complex [H‐ 2 ] + , unambiguously identified by NMR spectroscopy at low temperature. All isolated products were characterized by multinuclear NMR spectroscopy, IR, MS, and single‐crystal X‐ray crystallography in the cases of complexes 4 a , 4 e , 6 a , and 16 a . Furthermore, ESI‐MS/MS studies on primarily formed reactive intermediates and DFT studies on the reaction mechanism are presented.

Charge‐State‐Dependent Fragmentation of [2.2]Based Metallosupramolecular Cyclic Helicates in the Gas Phase

Abstract A detailed mass‐spectrometric study provides insight into the gas‐phase fragmentation pathways of a cyclic helicate selectively built from four iron(II) centers and six [2.2]cyclophane‐based ligands through the subcomponent self‐assembly approach. The charge state of the precursor ion, i. e., the number of triflate anions accompanying the metallo‐supramolecular core, has a strong influence on the observed fragmentations. The triply charged ion shows loss of a neutral ligand whereas ions of higher charge fragment by up to three different charge‐separating pathways to minimize the charge density of the ions. Additional subsequent fragmentations of highly charged fragment ions include redox processes as well as splitting of the unusual paracyclophane backbone.