A possible interaction effect in graphite

It is shown that there appears to be a significant correlation between one of the supposed minority carrier de Haas-van Alphen frequencies in graphite and the difference of the majority electron and hole frequencies.     

The capture of inner-shell electrons in the strong-potential born (SPB) approximation

For the first time the capture of inner-shell electrons by protons is calculated by the SPB method without further approximation and using Hartree-Slater wavefunctions. The resulting cross-section has roughly the correct shape, but is much too large. The problem is traced to a loss of normalization caused by the SPB approximation. A suitably renormalized SPB gives close agreement with experiment.     

Ionic liquids in vacuo; solution-phase X-ray photoelectron spectroscopy

The in situ monitoring of catalysis in Room Temperature Ionic Liquids (RTILs) is fundamental to the understanding of catalytic processes and the role of RTILs in catalytic turnover; we describe how XPS can be used to give information on both pure RTILs and catalytically-active RTIL-based solutions.     

Chemistry of the podocarpaceae—X Synthesis of podospicatin and its trimethyl ether

Podospicatin (I) and its trimethyl ether (II) have been synthesized by separate standard procedures respectively, involving in the former a rearrangement with alkali.     

Determination of perchlorate in samples of potassium chlorate. I

Summary A method has been developed for the determination of small amounts of potassium perchlorate in admixture with potassium chlorate. The method involves preliminary decomposition of the potassium chlorate by boiling with concentrated hydrochloric acid, preparing a disc from the dried residue, and measuring its absorbance at 628 cm^–1.

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Zusammenfassung Eine Methode zur Bestimmung kleiner Mengen Kaliumperchlorat in Gegenwart von Kaliumchlorat wurde ausgearbeitet. Sie beruht auf der vorhergehenden Zersetzung des Chlorats durch Kochen mit konz. Salzsäure, Herstellung einer Scheibe aus dem Trockenrückstand und Messung ihrer Absorption bei 628 cm^–1.

     

Absorption spectra of quantum aggregates interacting via long-range forces

We present a simple formula by which the shape of the absorption spectrum of an aggregate of quantum "monomers" (cold atoms, molecules, quantum dots, nanoparticles, etc.) interacting via dipole-dipole forces can be calculated from the averaged spectrum of the quantum monomer itself. Spectral broadening, due to a wide variety of causes, is included explicitly so that the formula is applicable not only to the idealization of a discrete spectrum but also to the practical situation of a continuously broadened spectrum. In simple cases, analytic results are obtained showing the strong dependence of the aggregate spectrum on the precise nature of the broadening of the quantum monomer spectrum. The formula is compared with results of exact diagonalization of model aggregate Hamiltonians and with experiment.     

Synthesis of Sulfonimidamides from Sulfenamides via an Alkoxy‐amino‐λ6‐sulfanenitrile Intermediate

Sulfonimidamides are intriguing new motifs for medicinal and agrochemistry, and provide attractive bioisosteres for sulfonamides. However, there remain few operationally simple methods for their preparation. Here, the synthesis of NH‐sulfonimidamides is achieved directly from sulfenamides, themselves readily formed in one step from amines and disulfides. A highly chemoselective and one‐pot NH and O transfer is developed, mediated by PhIO in iPrOH, using ammonium carbamate as the NH source, and in the presence of 1 equivalent of acetic acid. A wide range of functional groups are tolerated under the developed reaction conditions, which also enables the functionalization of the antidepressants desipramine and fluoxetine and the preparation of an aza analogue of the drug probenecid. The reaction is shown to proceed via different and concurrent mechanistic pathways, including the formation of novel S≡N sulfanenitrile species as intermediates. Several alkoxy‐amino‐λ⁶‐sulfanenitriles are prepared with different alcohols, and shown to be alkylating agents to a range of nucleophiles.     

Switchable ErSc2N rotor within a C80 fullerene cage: an electron paramagnetic resonance and photoluminescence excitation study

Motivated by the possibility of observing photoluminescence and electron paramagnetic resonance from the same species located within a fullerene molecule, we initiated an EPR study of Er3+ in ErSc2N@C80. Two orientations of the ErSc2N rotor within the C80 fullerene are observed in EPR, consistent with earlier studies using photoluminescence excitation (PLE) spectroscopy. For some crystal field orientations, electron spin relaxation is driven by an Orbach process via the first excited electronic state of the 4I(15/2) multiplet. We observe a change in the relative populations of the two ErSc2N configurations upon the application of 532 nm illumination, and are thus able to switch the majority cage symmetry. This photoisomerization, observable by both EPR and PLE, is metastable, lasting many hours at 20 K.     

Monitoring dendrimer conformational transition using 19F and 1H2O NMR

The conformational transition of a fluorinated amphiphilic dendrimer is monitored by the ¹H signal from water, alongside the ¹⁹F signal from the dendrimer. High-field NMR data (chemical shift δ, self-diffusion coefficient D, longitudinal relaxation rate R₁, and transverse relaxation rate R₂) for both dendrimer (¹⁹F) and water (¹H) match each other in detecting the conformational transition. Among all parameters for both nuclei, the water proton transverse-relaxation rate R₂(¹H₂O) displays the highest relative scale of change upon conformational transition of the dendrimer. Hydrogen/deuterium-exchange mass spectrometry reveals that the compact form of the dendrimer has slower proton exchange with water than the extended form. This result suggests that the sensitivity of R₂(¹H₂O) toward dendrimer conformation originates, at least partially, from the difference in proton exchange efficiency between different dendrimer conformations. Finally, we also demonstrated that this conformational transition could be conveniently monitored using a low-field benchtop NMR spectrometer via R₂(¹H₂O). The ¹H₂O signal thus offers a simple way to monitor structural changes of macromolecules using benchtop time-domain NMR.