“Higher density does not mean higher stability” mystery of paracetamol finally unraveled

Abstract

Topological analysis of the experimental electron density distribution functions for two polymorphs of paracetamol showed that strong H-bonds are responsible for the higher stability of crystal phase I, weak interactions for the higher density of phase II. This made it possible to finally resolve the contradiction between the relative stabilities and the densities of the two paracetamol polymorphs.

A New Class of Homogeneous Visible‐Light Photocatalysts: Molecular Cerium Vanadium Oxide Clusters

“…27 Having a very simple form as 0.5 v (r), it has been repeatedly shown to give accurate estimates in many cases (those are succinctly summarized in28), including weak interactions such as H ⋅⋅⋅ H and CH ⋅⋅⋅ O46 or CH ⋅⋅⋅ N,14 Mg ⋅⋅⋅ C and Ca ⋅⋅⋅ C interactions,47, 48 strong and intermediate H‐bonds,49 CaO(carbonate),50 AuPPh 3 and GdOH 2 bonds,51, 52 and so on 28. The interaction energies thus obtained have been shown to accurately reproduce the energy of a crystal lattice;14, 46, 50, 53, 54 the discrepancy between the crystal lattice energies estimated in such a manner from X‐ray diffraction data and those measured experimentally can be as small as 0.2 kcal mol −1 35. 46…”

“…Thus, an H‐bond in the above‐mentioned [Cu 3 (CO 3 ) 2 (OH) 2 ],33 which is not so short and directional (O ⋅⋅⋅ O 2.9817(8) Å, OHO 150 °) and occurs between two like‐charged species, has a much lower energy of 1.7 kcal mol −1 , and an E int value of 2.1 kcal mol −1 has been assigned to a NH ⋅⋅⋅ O bond in the above [NH 3 OH]Cl20 (N ⋅⋅⋅ O 2.9780(4) Å, NHO 105(1) °). The estimated energies for GuaCO 3 agree, however, with those in molecular systems, such as polymorphs of paracetamol with similar NH ⋅⋅⋅ O bonds (N ⋅⋅⋅ O 2.9040(4) and 2.9354(4) Å, NHO 163(1) and 162(1) °, 6.0 and 4.6 kcal mol −1 ); the accuracy of energy evaluation for the latter has been proved by a good agreement between total interaction energies and experimental sublimation enthalpies of the two polymorphs 35…”

Cation–π and Lone Pair–π Interactions Combined in One: The First Experimental Evidence of (H3O‐lp)+⋅⋅⋅π‐System Binding in a Crystal

“…It allows detecting any bonding interaction, [24] accurately estimating its energy, [25][26][27][28][29] obtaining atomic charges and localizing electron lone-pair domains [24,30,31] in a system in the isolated state or a crystal. This approach has already been applied to investigate cation-p, [32] anion-p, [33][34][35] and lone pair-p interactions between neutral molecules; [8] therefore, we have carried out an AIM analysis of the 1(r) function derived from the highresolution XRD data for 1.…”

“…[36] In the AIM classification, all these interactions (see Table S1 of gies (E int ) were quantified using Espinosa's correlation [25,26] based on the XRD data, which allows the strength of both H bonds (whether classic or ionic) [23,37] and weak interactions [27,29] in a crystal to be assessed accurately. According to the values obtained (see Table S1 of the Supporting Information), the H 3 O + ···p interaction in 1 is rather weak, with the energy at 1.2 kcal mol…”

Experimental Charge Density Evidence for Pnicogen Bonding in a Crystal of Ammonium Chloride

“…[32] The interaction energies thus obtained were shown to accurately reproduce the energy of a crystal lattice, [57,58,62,65,66] the discrepancy between the crystal lattice energies estimated in such a manner from X-ray diffraction data and those measured experimentally can be as small as 0.2 kcal mol À1 . [57,67] PW-DFT calculations were carried out by using the VASP 5.3.3 program; [68][69][70][71] exchange and correlation parts of the total energy were described by means of PBE functional. [54] Optimization of atomic positions (when applicable) has been started from the experimental data by using a plane wave basis set (with a kinetic energy cutoff of 1360 eV).…”