Chemistry – A European Journal
ISSN / EISSN : 0947-6539 / 1521-3765
Published by: Wiley (10.1002)
Total articles ≅ 40,402
Latest articles in this journal
Chemistry – A European Journal; doi:10.1002/chem.202101946
We present detailed studies on the covalent adsorption of molecular oxygen and atomic hydrogen on the hexagonal boron nitride ( h ‑BN) nanomesh on Rh(111). The functionalization of this two-dimensional (2D) material was investigated under ultra-high vacuum conditions using synchrotron radiation-based in situ high-resolution X-ray photoelectron spectroscopy, temperature-programmed X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. We are able to provide a deep insight into the adsorption behavior and thermal stability of oxygen and hydrogen on h ‑BN/Rh(111). Oxygen functionalization was achieved via a supersonic molecular beam while hydrogen functionalization was realized using an atomic hydrogen source. Adsorption of the respective species was observed to occur selectively in the pores of h -BN leading to spatially defined modification of the 2D layer. The adsorption of the observed molecular oxygen species was found to be an activated process that requires high-energy oxygen molecules. Upon heating to 700 K, oxygen functionalization was observed to be almost reversible except for small amounts of boron oxides evolving due to the reaction of oxygen with the 2D material. Hydrogen functionalization of h ‑BN/Rh(111) was fully reversed upon heating to about 640 K.
Chemistry – A European Journal; doi:10.1002/chem.202101968
A new type of «Geländer»-molecule based on a ortho -tetraphenylene core is presented. The central para -quaterphenyl backbone is wrapped by a 4,4'-di(( Z )-styryl)-1,1'-biphenyl banister, with its aryl rings covalently attached to all four phenyl rings of the backbone. The resulting helical chiral bicyclic architecture consist exclusively of sp 2 hybridized carbon atoms. The target structure is assembled by expanding the central ortho -tetraphenylene subunit with the required additional phenyl rings followed by a twofold macrocyclization. First macrocyclization attempts based on a twofold McMurry coupling are successful but low yielding, while the second strategy profiting from olefin metathesis provide satisfying yields. Hydrogenation of the olefins results in a saturated derivative of similar topology, allowing to study the interdependence between saturation and physico-chemical properties. The target structures are fully characterized including their solid state structures. The helical chiral bicycle is synthesized as racemate and separated into pure enantiomers by HPLC on a chiral stationary phase. Comparison of recorded and simulated chiroptical properties allows the assignment of the enantiomers.
Chemistry – A European Journal; doi:10.1002/chem.202102164
The molecular level description of carbohydrate assemblies is hampered by their structural complexity and the lack of suitable analytical methods. Here, we employed systematic chemical modifications to identify key non-covalent interactions that triggered the supramolecular assembly of a disaccharide model. While some modifications disrupted the supramolecular organization, others were tolerated, delivering important information on the aggregation process. The screening identified new geometries, including nanotubes, and twisted ribbons that were characterized with electron tomography and electron diffraction (ED) methods. This work demonstrates that the combination of synthetic chemistry and ED-methods is a powerful tool to draw correlations between the molecular structure and the nanoscale architecture of carbohydrate assemblies.
Chemistry – A European Journal, Volume 27; doi:10.1002/chem.202183961
Zirconium-based metal-organic framework materials (Zr−MOFs) have more practical usage over most conventional benchmark porous materials and even many other MOFs due to the excellent structural stability, rich coordination forms, and various active sites. However, their mass-production and application are restricted by the high-cost raw materials, complex synthesis procedures, harsh reaction conditions, and unexpected environmental impact, and considerable green chemistry efforts have been applied breaking through the limitations, and significant progress has been made in the sustainable synthesis of Zr−MOFs over the past decade. For more information, see the Review by J. Fu and Y. Wu on page 9967.
Chemistry – A European Journal, Volume 27; doi:10.1002/chem.202183962
Selective incorporation of deuterium into small molecules has emerged as a new challenge to chemists due to an increasing demand for deuterium-labeled organic molecules. For this purpose, commercial or readily synthesized deuterium donors are employed as easy-to-handle reagents for transfer deuteration and hydrodeuteration reactions. Read more about recent advances in the catalytic transfer deuteration and hydrodeuteration for the selective synthesis of deuterated compounds in the Minireview by J. R. Clark et al. on page 9988 ff.
Chemistry – A European Journal; doi:10.1002/chem.202102391
Chromium based single-site catalysts allow the production of ultra-high molecular weight polyethylene with very high productivities. The picture shows a donor-functionalised indenyl chromium catalyst in action where a strong electron-donating substituent leads to an increase in catalytic activity and co-monomer incorporation. The correlation between donor strength, electronic and catalytic properties was studied systematically. More information can be found in the Full Paper by M. Enders et al. (DOI: 10.1002/chem.202101586).
Chemistry – A European Journal; doi:10.1002/chem.202102076
We compare three methods for quantitatively distinguishing the location of noble metals (NM) in mesopores from those found on the external particle surface. MCM-41 and SBA-15 with NM either preferentially located in mesopores or on the external surface were prepared and characterized by TEM. We quantified arylphosphines forming complexes with NM by 31 P MAS NMR spectroscopy. Phosphine/NM ratios drop from 2.0 to 0.2 when increasing the probe diameter from 1.08 to 1.54 nm. The reaction between NM and triphenylphosphine (TPP) within 3.0 nm MCM-41 pores takes due to confinement effects multiple weeks. In contrast, external NM react with TPP instantly. A promising method is filling the pores using the pore volume impregnation technique with tetraethylorthosilicate (TEOS). TPP loading revealed that 66% of NM are located on the external surface of MCM-41. The pore filling method can be used in association with any probe molecule, also for the quantification of acid sites.
Chemistry – A European Journal; doi:10.1002/chem.202102457
We report a pH- and temperature-controlled reversible self-assembly of Au-nanoparticles (AuNPs) in water, based on their surface modification with cationic guanidiniocarbonyl pyrrole (GCP) and zwitterionic guanidiniocarbonyl pyrrole carboxylate (GCPZ) binding motifs. When both binding motifs are installed in a carefully balanced ratio, the resulting functionalized AuNPs self-assemble at pH 1, pH 7 and pH 13, whereas they disassemble at pH 3 and pH 11. Further disassembly can be achieved at elevated temperatures at pH 1 and pH 13. Thus, we were able to prepare functionalized nanoparticles that can be assembled/disassembled in seven alternating regimes, simply controlled by pH and temperature.
Chemistry – A European Journal, Volume 27; doi:10.1002/chem.202183963
The term “molecular square” has been applied to many species, but are they truly planar as a mathematician would require? This work probes this conundrum for a series of Pt4C16 complexes with platinum(II) corners and butadiynediyl or −C≡C−C≡C− edges. In fact, both planar and puckered energy minima are found, both by DFT calculations and crystallographically. Thus, mimicking the grace of a butterfly in flight, these structures can easily transit between extended and folded geometries. For more details see the Full Paper by J. A. Gladysz, M. B. Hall et al. on page 10021 ff.
Chemistry – A European Journal; doi:10.1002/chem.202102390
The synthesis and isolation of a phosphinine selenide was achieved for the first time by reacting red selenium with 2,6-bis(trimethylsilyl)phosphinine. The rather large coupling constant of 1 J P,Se = 883 Hz is in line with a P-Se bond of high s -character. The σ-electron donating Me 3 Si-substituents significantly increase the energy of the phosphorus lone pair and hence its basicity, making the heterocycle considerably more basic and nucleophilic than the unsubstituted phosphinine C 5 H 5 P, as confirmed by the calculated gas phase basicities. NBO calculations further reveal that the lone pairs of the selenium atom are stabilized through donor-acceptor interactions with antibonding orbitals of the aromatic ring. Our results pave the way for new perspectives in the chemistry of phosphorus in low coordination.