Stark wirksam bei geringen Nebenwirkungen: In der Anästhesie dienen Muskelrelaxantien zum Einstellen guter Intubationsbedingungen über eine tiefe neuromuskuläre Blockade; am häufigsten wird hierfür Rocuroniumbromid verwendet. Die hierdurch hervorgerufene neuromuskuläre Blockade wird durch die Bildung eines fest gebundenen, binären Komplexes (Ka≈ 107 M−1) zwischen dem Gastmolekül Rocuroniumbromid und einer synthetischen Wirtverbindung auf Cyclodextrinbasis (siehe Struktur im Kristall) aufgehoben. Im Hinblick auf Wirksamkeit und geringe Nebenwirkungen ist dieses Wirkstoff‐System den derzeit klinisch verwendeten überlegen.

Crystal clear: A detailed conformational characterization of a synthetic analogue of the peptide antibiotic alamethicin (see structure; C gray, N blue, O red) has been achieved by X‐ray diffraction. The high‐resolution structure of this analogue, which incorporates a spin probe, paves the way for a better understanding of the mode of action of alamethicin.

Reaction of indole with Br 2 led to isolation of an indole trimer 2, formed by linking the 2-and 3-positions of each indole to form a central aromatic ring, and brominated at the 5-and 6-positions of each indole. The Xray structure of [2]?acetone?2DMF showed p-stacking of the planar aromatic molecules with two different overlap modes with interplanar distances of 3.287 A Ê and 3.378 A Ê . Cyclic voltammetry showed one reversible oxidation for 2 and phosphorescence from frozen ethanol solution was observed. The X-ray structure of the adduct [2][TCNQ] 2 ?4DMSO was determined and showed a mixed stack arrangement where 2 alternates with two adjacent TCNQ molecules.

No abstract

Dynamic properties of the hydrogen-bonding arrangement in a selectively deuterated sample of solid triphenylmethanol (Ph3COD) have been studied by wide-line 2H NMR spectroscopy. In the crystal structure of Ph3COD, the molecules form hydrogen-bonded tetramers, with the oxygen atoms positioned approximately at the corners of a tetrahedron. The tetramer has point symmetry C 3 (rather than T d ); three of the Ph3COD molecules (denoted as “basal”) are related to each other by a 3-fold rotation axis, and the fourth molecule (denoted as “apical”) lies on this axis. Thus, the oxygen atoms from the four molecules in the tetramer form a pyramidal arrangement with an equilateral triangular base, and the O···O distances are consistent with the tetramer being held together by O−H···O hydrogen bonds. The 2H NMR line shape for Ph3COD varies with temperature (in the range 97− 373 K), demonstrating clearly that the hydrogen-bonding arrangement is dynamic. Several plausible dynamic models are proposed, and it is found that only one model gives a good fit to the experimental 2H NMR spectra across the full temperature range studied. In this model, the deuteron of the apical molecule undergoes a three-site 120° jump motion by rotation about the C−O bond (with equal populations of the three sites), whereas the deuterons of the basal molecules undergo a two-site 120° jump motion, by rotation about their C−O bonds. In addition, each deuteron undergoes rapid libration (reorientation about the relevant C−O bond) with the libration amplitude increasing as a function of temperature. The behavior of the basal molecules is interpreted in terms of the existence of two possible hydrogen-bonding arrangementsdescribed as “clockwise” and “anticlockwise”on the basal plane of the pyramid. The two-site 120° jump motion for the basal molecules “switches” between these two hydrogen-bonding arrangements and clearly requires correlated jumps of the hydroxyl groups of all three basal molecules. On the assumption of Arrhenius behavior for the temperature dependence of the jump frequencies, the activation energies for the jump motions of the apical and basal deuterons are estimated to be 10 and 21 kJ mol-1 respectively. This dynamic model is further supported by (i) analysis of the dependence of the quadrupole echo 2H NMR line shape on the echo delay and (ii) consideration of 2H NMR spin−lattice relaxation time (T 1) data. A full physical interpretation and justification of this dynamic model is presented.