Necessity and Pitfalls of Low-Temperature Measurements

Larsen, Finn

doi:10.1007/978-1-4615-3700-7_8

Cited by 2 publications

(1 citation statement)

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“…We emphasize here one feature of the model that we have adopted to analyze the measured X-ray intensities, that is, the anisotropic vibrational motion of the hydrogen nuclei. Indeed, as hydrogen atoms are critical for both the molecular electrostatic properties and the chemical reactivity, [18,19] accuracy in their positional and displacement parameters is crucial in electrondensity studies of molecular crystals.…”

Section: Introductionmentioning

confidence: 99%

Progress in the Understanding of Drug–Receptor Interactions, Part 1: Experimental Charge‐Density Study of an Angiotensin II Receptor Antagonist (C₃₀H₃₀N₆O₃S) atT=17 K

Destro

Soave

Barzaghi

et al. 2005

Chemistry A European J

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An experimental study of the electron-density distribution rho(r) in an angiotensin II receptor antagonist 1 has been made on the basis of single-crystal X-ray diffraction data collected at a low temperature. The crystal structure of 1 consists of infinite ribbons in which molecules are connected by an N-H...N hydrogen bond and several interactions of the C-H...O, C-H...N, and C-H...S type. The molecular conformation, characterized by the syn orientation of a tetrazole and a pyrimidinone ring with respect to a phenyl spacer group, is stabilized by two short SO and SN intramolecular contacts between a substituted thiophene fragment and the other two heterocycles of 1. The electrostatic nature of these interactions is documented. Furthermore, the Laplacian of rho(r) in the plane defined by the sulfur, oxygen, and nitrogen atoms involved in these interactions shows their strongly directional character as the regions of charge concentration on the valence shell of the nitrogen and oxygen atoms directly face the regions of charge depletion on the valence shell of the sulfur atom. All the chemical bonds and the relevant intra- and intermolecular interactions of 1 have been quantitatively described by the topological analysis of rho(r). Simple relationships between the bond path lengths (R(b)) and the values of rho at the bond critical points (rho(bcp)) have been obtained for the 28 C-C bonds, the seven N-C bonds, and the four O-C bonds. For the first two classes of bonds the relationship is in the form of a straight line, whose parameters, for the C-C bonds, agree, within experimental uncertainty, with those previously derived in our laboratory from a 19 K X-ray diffraction study of crystals of a different compound. Maps of the molecular electrostatic potential phi(r) derived from the experimental charge density display features that are important for the drug-receptor recognition of 1.

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Section: Introductionmentioning

confidence: 99%