Polysulfonylamine. CLXXXIV. Kristallstrukturen molekularer Triphenylphosphangold(I)‐di(4‐X‐benzolsulfonyl)‐amide: Isomorphie und dichte Packung (X = Me,F, Cl,NO2) vs. struktursteuernde Halogenbrücken C–X···Au/O (X = Br,I)

Polysulfonylamines. CLXXXIV. Crystal Structures of Molecular Triphenylphosphanegold(I) Di(4‐X‐benzenesulfonyl)amides: Isomorphism and Close Packing (X = Me, F, Cl, NO₂) vs. Structure‐Determining C–X···Au/O Halogen Bonds (X = Br, I) In order to study the structure‐determining influence that halogen bonding can exert during the course of crystallization, solid‐state structures are compared for two previously reported and four new molecular gold(I) complexes of the type Ph₃P–Au–N(SO₂–C₆H₄–4‐X)₂, each featuring linear P,N coordination at gold and two phenyl rings with varying p‐substituents X = Me, F, Cl, NO₂, Br or I. The compounds were synthesized by reactions of Ph₃PAuX (X = Cl or I) with the corresponding silver di(arenesulfonyl)amides, crystallized from dichloromethane, and characterized by low‐temperature X‐ray diffraction. The Me, F, Cl and NO₂ congeners are isomorphic and crystallize without solvent inclusion in the chiral orthorhombic space group P2₁2₁2₁ (Z′ = 1). These structures are governed by isotropic close packing via three‐dimensional 2₁ symmetry, incidentally supported by an invariant set of C–H···O=S hydrogen bonds, CH/π interactions and π/π stackings of aromatic rings; in particular, the hard halogen atoms of the fluoro and the chloro homologues are not involved in X···Au, X···O or X···X interactions. The higher homologues, with soft halogen atoms, were obtained as a dichloromethane hemisolvate for X = Br and a corresponding monosolvate for X = I, each triclinic in the centrosymmetric space group (Z′ = 1). Here, the primary structural effect is implemented by infinite chains in which translation‐related molecules are connected for the bromo compound by a bifurcated Au···Br(2)···O=S interaction, for the iodo congener by an equivalent Au···I(2)···O=S interaction and a short halogen bond C–I(1)···O=S. The latter bond is stronger than a similar C–Br···O=S interaction and induces a conformational adjustment of the (CSO₂)₂N group from the normal twofold symmetry in the bromo compound to an energetically unfavourable asymmetric form in the iodo homologue. In both cases, pairs of antiparallel molecular catemers are associated into strands via sixfold phenyl embraces, the strands are stacked to form layers, the solvent molecules are intercalated between adjacent layers, and the crystal packings are reinforced by a number of C–H···O=S hydrogen bonds and interactions of aromatic rings.     

Aquatic passive sampling of a short-term thiacloprid pulse with the Chemcatcher: impact of biofouling and use of a diffusion-limiting membrane on the sampling rate

We examined the performance of the Chemcatcher (University Portsmouth, UK) in two different configurations when used for the aquatic passive sampling of a 1-day pulse contamination with thiacloprid under field-relevant conditions. The configuration without diffusion-limiting membrane led to biofouling of the Empore disk receiving phase resulting in a fourfold reduction in analyte uptake compared to unfouled passive samplers. The sampling rate for the configuration with diffusion-limiting polyethersulfone membrane was also much lower than in a long-term exposure scenario, although no biofouling occurred. Both configurations of the Chemcatcher exhibited high variation in analyte uptake with up to 100% RSD. Short-term contamination events may be underestimated in passive sampling when the receiving phase is biofouled or a diffusion-limiting membrane is employed.     

Mechanistic and kinetic insights into the thermally induced rearrangement of alpha-pinene

The thermal rearrangement of alpha-pinene (1) is interesting from mechanistic as well as kinetic point of view. Carrier gas pyrolyses with 1 and its acyclic isomers ocimene (2) and alloocimene (3) were performed to investigate the thermal network of these hydrocarbons. Kinetic analysis of the major reaction steps allows for a deeper insight in the reaction mechanism. Thus it was possible to explain the racemization of 1, the formation of racemic limonene (4), and the absence of the primary pyrolysis product 2 in the reaction mixture resulting from thermal rearrangement of 1. Results supported the conclusion that the reactions starting with 1 involve biradical transition states.     

Protodesilylation of 2,6-disubstituted silyphosphinines. Experimental and theoretical study

2,6-Disilylphosphinines react with HCl in ethereal solution to cleanly yield the corresponding 2,6-unsubstituted derivatives. DFT calculations allowed rationalization of the mechanism of this protodesilylation.     

Synthesis,structure and characterization of [Mg7(μ3-OCH2CH2OMe)6(μ-OCH2CH2OMe)6][Al(n-Bu)4]2 – A cationic heptanuclear magnesium complex consisting of discrete cations and tetrabutylaluminate anions

Dibutylmagnesium (contaminated with Al(n-Bu)₃; n_Mg:n_Al ca. 1:0.2) was found to react with MeOCH₂CH₂OH followed by the addition of PhSCH(Me)Ph in the presence of 0.2 equiv n-butyllithium yielding [Mg₇(μ₃-OCH₂CH₂OMe)₆(μ-OCH₂CH₂OMe)₆][Al(n-Bu)₄]₂ (1) as the principal product (yield 40–45% referred to MeOCH₂CH₂OH). The single-crystal X-ray diffraction analysis revealed that the centrosymmetric cationic heptamagnesium complex is built up from seven edge-shared MgO₆ octahedra. The [Al(n-Bu)₄]⁻ anions adopt approximately a tetrahedral AlC₄ symmetry. ¹H, ¹³C and ²⁷Al NMR spectroscopic measurements showed that in THF solution the structures both of the heptamagnesium complex and the tetrabutylaluminate anion are preserved and that there are no cation–anion interactions reducing the symmetry. The ²⁷Al resonance (151.6 ppm) was found to be very sharp (w_1/2 = 5 Hz), the coupling constant ¹J(²⁷Al,¹³C) amounts to 72.3 Hz.     

A Covalent Binding Mode of a Pyrazole-Based CD38 Inhibitor

Brain concentrations of nicotinamide adenine dinucleotide (NAD⁺), an important cellular co-factor, tend to decrease with age and in neurodegeneration. As the NADase cluster of differentiation 38 (CD38) significantly contributes to NAD⁺ consumption, we reasoned that CD38 inhibition may be of therapeutic value for CNS disorders. The new pyrazole compound was designed based on a known CD38 inhibitor and showed good inhibitory potency. Several attempts to co-crystallise this pyrazole with CD38 and cyclic adenosine diphosphate ribose (cADPR) culminated in a high-resolution X-ray structure, in which the pyrazolyl group in the new compound formed a covalent bond with one of the ribosyl units of cADPR. This reaction proceeded under retention of configuration and resulted in a neutral ribosyl-pyrazole conjugate that is embedded within the active site of the enzyme. An analysis of this structural complex gave rise to design principles that enabled the preparation of more potent CD38 inhibitors with drug-like properties.     

Combining Deep Eutectic Solvents with TEMPO-based Polymer Electrodes: Influence of Molar Ratio on Electrode Performance**

For sustainable energy storage, all-organic batteries based on redox-active polymers promise to become an alternative to lithium ion batteries. Yet, polymers contribute to the goal of an all-organic cell as electrodes or as solid electrolytes. Here, we replace the electrolyte with a deep eutectic solvent (DES) composed of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and N-methylacetamide (NMA), while using poly(2,2,6,6-tetramethylpiperidin-1-yl-oxyl methacrylate) (PTMA) as cathode. The successful combination of a DES with a polymer electrode is reported here for the first time. The electrochemical stability of PTMA electrodes in the DES at the eutectic molar ratio of 1 : 6 is comparable to conventional battery electrolytes. More viscous electrolytes with higher salt concentration can hinder cycling at high rates. Lower salt concentration leads to decreasing capacities and faster decomposition. The eutectic mixture of 1 : 6 is best suited uniting high stability and moderate viscosity.     

A kinetic study of guest displacement reactions on a host-guest complex with a photoswitchable calixarene

The displacement processes of several guests, incorporated in a calixarene host system, were investigated in the gas phase by electrospray ionization-Fourier transform-ion cyclotron resonance (ESI-FT-ICR) mass spectrometry. The complexes resulting from a resorcin[4]arene host with ammonia and sec-butylamine guests were isolated in an ICR-cell, separately using both states of the photoswitch as well as two reference systems for the open and closed forms of the photoswitchable host. The isolated complexes were forced to exchange the guest by using methylamine, ethylamine and sec-butylamine, resulting in different reaction rates for all the measured systems. Especially, the reaction rates of both states of the photoswitch are dependent on the provided guest. Potential side effects like proton exchanges were examined by an H/D-exchange experiment. The results were investigated and supported by quantum chemical calculations (DFT).