Parasitics Extraction With Multipole Refinement

The tetraphenylphosphonium squarate salt crystallizes with a number of diverse interactions, which all have the potential to be classified as hydrogen bonds. The squarate anions are found as dimers linked by O-H···O interactions. The multipole refinement of the tetraphenylphosphonium squarate was performed using the HansenCoppens model followed by topological analysis of its intermolecular interactions. A total of 28 interactions were found among the symmetry related molecules, which include a number of C-H···Cπ, C-H···O, and C-H···H-C interactions, along with the O-H···O interaction. With the criteria for hydrogen bonding proposed by Popelier and Koch, it is possible to determine which of these interactions are hydrogen bonds and which are van der Waals interactions. Both linear and exponentially dependent correlations can be seen for the properties of the bond critical points involving the intermolecular interactions that fulfill these criteria. All this leads to a better understanding of the role that hydrogen bonds play in the formation of small organic compounds.Key words: electron density, multiple refinement, hydrogen bonds.

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Experimental electron density study of ethylene oxide at 100 K

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768108010197 ◽

2008 ◽

Vol 64 (3) ◽

pp. 397-400 ◽

Cited By ~ 9

Author(s):

Simon Grabowsky ◽

Manuela Weber ◽

Jürgen Buschmann ◽

Peter Luger

Keyword(s):

Ethylene Oxide ◽

Electron Density ◽

Density Functional ◽

High Strain ◽

Membered Ring ◽

Topological Properties ◽

X Ray ◽

Multipole Refinement ◽

Experimental Electron Density ◽

Density Study

The experimental electron density of ethylene oxide was derived from a multipole refinement of 100 K X-ray data and complemented by density-functional calculations at experimental and optimized geometry. Atomic and bond-topological properties were derived using the atoms-in-molecules (AIM) formalism. The high strain in the three-membered ring molecule is mainly expressed by the high ellipticities of the three bonds in this ring, while the bond paths are only slightly bent for the C—C bond, but are virtually straight for the C—O bond.

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Charge Density of L-Alanyl-glycyl-L-alanine Based on X-Ray Data Collection Periods from 4 to 130 Hours

Zeitschrift für Naturforschung B ◽

10.1515/znb-2007-0512 ◽

2007 ◽

Vol 62 (5) ◽

pp. 696-704 ◽

Cited By ~ 5

Author(s):

Diana Förster ◽

Armin Wagner ◽

Christian B. Hübschle ◽

Carsten Paulmann ◽

Peter Luger

Keyword(s):

Synchrotron Radiation ◽

Low Temperature ◽

Charge Density ◽

Data Sets ◽

Data Set ◽

X Ray ◽

Atomic Properties ◽

Multipole Refinement ◽

Refinement Strategy ◽

Experimental Charge Density

Abstract The charge density of the tripeptide L-alanyl-glycyl-L-alanine was determined from three X-ray data sets measured at different experimental setups and under different conditions. Two of the data sets were measured with synchrotron radiation (beamline F1 of Hasylab/DESY, Germany and beamline X10SA of SLS, Paul-Scherer-Institute, Switzerland) at temperatures around 100 K while a third data set was measured under home laboratory conditions (MoKα radiation) at a low temperature of 20 K. The multipole refinement strategy to derive the experimental charge density was the same in all cases, so that the obtained charge density properties could directly be compared. While the general analysis of the three data sets suggested a small preference for one of the synchrotron data sets (Hasylab F1), a comparison of topological and atomic properties gave in no case an indication for a preference of any of the three data sets. It follows that even the 4 h data set measured at the SLS performed equally well compared to the data sets of substantially longer exposure time.

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