Gas-phase computational study of tetra-n-butylammonium ion conformational mobility

The energy profiles of various configurations of the tetra-n-butylammonium ion (Bu4N+) arising by changing the angle between a pair of butyl ligands, as well as by rotating of various alkyl fragments in gas phase, were calculated using DFT methods. A hypothesis about the most probable way of changing the conformations of tetra-n-butylammonium ions during the phase transitions in highly conductive solid electrolytes was proposed.

Свободное вращение простых молекул и характеристические температуры в стеклообразных полимерах

Purely rotational spectra of CO and HCl molecules added as a probe to polypropylene (PP) and polyvinyl chloride (PVC) were obtained and analyzed. It is shown that the shape of the bands of these spectra, which reflects the degree of disturbance of the rotational motion, is strongly influenced by the local dynamics of the polymer matrix. From the change in the integrated intensity of absorption with the temperature were found temperatures of the transition from free rotation of CO and HCl molecules to their libration, as well as the temperatures of the onset of defrosting of the conformational mobility of the chains of PP and PVC macromolecules.

MOF matrix isolation: cooperative conformational mobility enables reliable single crystal transformations

Preordering of the linker site and utilising framework flexibility are critical to achieving high levels of metal loading during post-synthetic metalation.

A Never-Ending Conformational Story of the Quercetin Molecule: Quantum-Mechanical Investigation of the O3′H and O4′H Hydroxyl Groups Rotations

The quercetin molecule is known to be an effective pharmaceutical compound of a plant origin. Its chemical structure represents two aromatic A and B rings linked through the C ring containing oxygen and five OH hydroxyl groups attached to the 3, 3′, 4′, 5, and 7 positions. In this study, a novel conformational mobility of the quercetin molecule was explored due to the turnings of the O3′H and O4′H hydroxyl groups, belonging to the B ring, around the exocyclic C-O bonds. It was established that the presence of only three degrees of freedom of the conformational mobility of the O3′H and O4′H hydroxyl groups is connected with their concerted behavior, which is controlled by the non-planar (in the case of the interconverting planar conformers) or locally non-planar (in other cases) TSsO3′H/O4′H transition states, in which O3′H and O4′H hydroxyl groups are oriented by the hydrogen atoms towards each other. We also explored the number of the physico-chemical and electron-topological characteristics of all intramolecular-specific contacts—hydrogen bonds and attractive van der Waals contacts at the conformers and also at the transition states. Long-terms perspectives for the investigations of the structural bases of the biological activity of this legendary molecule have been shortly described.

Cyclopentane rings in hydrophobic chains of a phospholipid enhance the bilayer stability to electric breakdown

Bilayers of a phospholipid with cyclopentane-containing chains are stable to pore formation due to restricted conformational mobility of the chains and inability of the molecules to rearrange in order to line the edge of a hydrophilic pore.