Showing papers by "Peter G. Schultz published in 2022"

Formation and Surface Behavior of Pt and Pd Complexes with Ligand Systems Derived from Nitrile‐functionalized Ionic Liquids Studied by XPS

Abstract: Abstract We studied the formation and surface behavior of Pt(II) and Pd(II) complexes with ligand systems derived from two nitrile‐functionalized ionic liquids (ILs) in solution using angle‐resolved X‐ray photoelectron spectroscopy (ARXPS). These ligand systems enabled a high solubility of the metal complexes in IL solution. The complexes were prepared by simple ligand substitution under vacuum conditions in defined excess of the coordinating ILs, [C3CNC1Im][Tf2N] and [C1CNC1Pip][Tf2N], to immediately yield solutions of the final products. The ILs differ in the cationic head group and the chain length of the functionalized substituent. Our XPS measurements on the neat ILs gave insights in the electronic properties of the coordinating substituents revealing differences in donation capability and stability of the complexes. Investigations on the composition of the outermost surface layers using ARXPS revealed no surface affinity of the nitrile‐functionalized chains in the neat ILs. Solutions of the formed complexes in the nitrile ILs showed homogeneous distribution of the solute at the surface with the heterocyclic moieties preferentially orientated towards the vacuum, while the metal centers are rather located further away from the IL/vacuum interface.

The Buoy Effect: Surface Enrichment of a Pt Complex in IL Solution by Ligand Design

Abstract: Abstract The targeted enrichment of a Pt complex with an ionic liquid (IL)‐derived ligand system in IL solution is demonstrated by using angle‐resolved X‐ray photoelectron spectroscopy. When the ligand system is complemented with fluorinated side chains, the complex accumulates strongly at the IL/gas interface, while in an equivalent solution of a complex without these substituents no such effect could be observed. This buoy‐like behavior induces strong population of the complex at the outermost molecular layer close to surface saturation, which was studied over a range from 5 to 30 %mol. The surface enrichment was found to be most efficient at the lowest concentration, which is particularly favorable for catalytic applications such as supported ionic‐liquid‐phase (SILP) catalysis.

Viscosity and Surface Tension of Fluorene and Perhydrofluorene Close to 0.1 MPa up to 573 K

Abstract: In the present study, the liquid viscosity and surface tension of fluorene (H0-F) and its fully hydrogenated counterpart perhydrofluorene (H12-F), representing process-relevant byproducts of the liquid organic hydrogen carrier (LOHC) system based on diphenylmethane and dicyclohexylmethane and potentially interesting LOHC compounds by themselves, were determined close to 0.1 MPa using different experimental methods. Besides surface light scattering (SLS) allowing for a simultaneous access to both properties up to 573 K, conventional methods in the form of capillary viscometry and pendant-drop tensiometry were applied up to (473 and 523) K, respectively. Furthermore, the liquid density of H12-F was measured by vibrating-tube densimetry from (283 to 473) K. While agreement of the viscosity and surface tension results obtained by SLS and the conventional methods is found in the case of H12-F, this is not given for H0-F, especially with respect to its surface tension, which seems to be caused by SLS-specific effects. H0-F exhibiting a melting point of about 384 K shows larger values for density, surface tension, and viscosity compared to H12-F being liquid at 283 K. The latter compound features stereoisomerism which appears to have a pronounced effect on the thermophysical properties. This could be deduced by comparison with the very limited amount of experimental data for the fluorene-based substances that are available in the literature so far. The extension of the thermophysical property database for H0-F and H12-F under process-relevant conditions can be useful for future studies, particularly in the field of chemical hydrogen storage.

Synthesis and biological evaluation of novel FiVe1 derivatives as potent and selective agents for the treatment of mesenchymal cancers.

Abstract: Epithelial-mesenchymal transition (EMT) endows stem cell-like properties to cancer cells. Targeting this process represents a potential therapeutic approach to overcome cancer metastasis and chemotherapy resistance. FiVe1 was identified from an EMT-based synthetic lethality screen and was found to inhibit the stem cell-like properties and proliferation of not only cancer cells undergoing EMT, but also more broadly in mesenchymal cancers that include therapeutically intractable soft tissue sarcomas. FiVe1 functions by directly binding to the type III intermediate filament protein vimentin (VIM) in a mode that induces hyperphosphorylation of Ser56, which results in selective disruption of mitosis and induced multinucleation in transformed VIM-expressing mesenchymal cancer cell types. Cell-based potency (IC50 = 1.6 μM, HT-1080 fibrosarcoma), poor solubility (<1 μM) and low oral bioavailability limits the direct application of FiVe1 as an in vivo probe or therapeutic agent. To overcome these drawbacks, we performed structure-activity relationship (SAR) studies and synthesized a set of 35 new compounds, consisting of diverse modifications of the FiVe1 scaffold. Among these compounds, 4e showed a marked improvement in potency (IC50 = 44 nM, 35-fold improvement, HT-1080) and cell type selectivity (19-fold improvement), when compared to FiVe1. Improvements in the potency of 4e, in terms of overall cytotoxicity, directly correlate with VIM Ser56 phosphorylation status and the oral bioavailability and pharmacokinetic profiles of 4e in mouse are superior to FiVe1. Successful optimization also resulted in potent and selective derivatives 11a, 11j and 11k, which exhibited superior pharmacological profiles, in terms of metabolic stability and aqueous solubility. Collectively, these optimization efforts have resulted in the development of promising FiVe1 analogs with potential applications in the treatment of mesenchymal cancers, as well as in the study of VIM-related biology.