The enrichment ratio of atomic contacts in crystals, an indicator derived from the Hirshfeld surface analysis

Abstract

An enrichment ratio is derived from the decomposition of the crystal contact surface between pairs of interacting chemical species. The propensity of different contact types to form is investigated.

Structural, Hirshfeld surface and theoretical analysis of two conformational polymorphs of N,N′-bis(pyridin-3-ylmethyl)oxalamide

“…The ER value corresponding to H ... H contacts is close to unity for 1 in accord with earlier published data [50]. By contrast, the corresponding values for molecules 1 and 2 of 2 are reduced to 0.78 and 0.81, respectively, showing a lower propensity for these contacts in the crystal structure.…”

“…The intermolecular interactions were further analysed using a new parameter, namely the enrichment ratio (ER) which is evaluated on the basis of Hirshfeld surface analysis [50]; the numerical values are listed in Table 5. The ER value corresponding to H ... H contacts is close to unity for 1 in accord with earlier published data [50].…”

Betulin Phosphonates; Synthesis, Structure, and Cytotoxic Activity

“…Self-contacts of O···O and Ho···Ho types are totally avoided in the packing as these interactions between charged atoms are electrostatic unfavorable. The enrichment ratios of contacts between pairs of chemical species are shown in Table 1; the ratios > 1 or < 1 indicate if contacts in the crystal packing are favored or disfavored, respectively [30]. Carbon is exposed on the molecular surface essentially in the C≡C-C (ester) region and C .…”

“…Chemical proportions S x on the Hirshfeld surface around the molecule in the crystal structure and decomposition of intermolecular contacts in pairs of atom types C xy . The enrichment values E xy are the ratios between C xy , the actual contact surfaces and those R xy computed as if all contacts were randomly distributed [30]. R xy equiprobable contacts are computed from S x values using probability laws.…”

Synthesis, structural and spectroscopic features, and investigation of bioactive nature of a novel organic-inorganic hybrid material 1H-1,2,4-triazole-4-ium trioxonitrate

“…The enrichment ratio (ER) of a pair of elements is then defined as the ratio between the proportion of actual contacts in the crystal and the theoretical proportion of random contacts [67]. The set of enrichment ratios of the various intermolecular contacts occurring in the 1H-1,2,4-triazol-4-ium nitrate compound are recorded in Table 4 (Table 4).…”