Supramolecular Similarity in Polymorphs: Use of Similarity Indices (I^X)

Abstract

A systematic investigation to assess the degree of similarity between polymorphs was carried out. A similarity indices (I X ) approach was applied in ten series of polymorphs with different characteristics and number of molecules in the asymmetric unit. Geometric (I D ), contact area (I C ), and stabilization energy (I G ) parameters were used. It was possible to situate each comparison in different regions of similarity within the polymorphism phenomenon and determine the boundaries between quasi-isostructural polymorphs and polymorphs of low similarity. The multiparameter I DCG index was used as a robust tool to determine the total similarity within the polymorphism phenomenon. The highest contribution of the stabilization energy parameter (45%) toward the final value of similarity (I DCG ) was observed, followed by the contact area index (32%). The geometric index contributed approximately 23% to the final value of I DCG . This information reinforces the importance of the contact area and stabilization energy in assessing the degree of similarity between crystalline structures. A new descriptor (I Q ) based on the comparison of the energetic contribution of intermolecular interaction types present in each crystal structure is presented. I Q can be a versatile tool and applicable even for systems that do not share any similarity.

Interplay between Conformation and Crystal Packing in Aryl Propargyl Ethers: Structural and Spectroscopic Properties of 2‐(prop‐2‐yn‐1‐yloxy)acene Derivatives

“…As discussed by Nangia (2008), when different conformers of the same molecule occur in different crystal forms, the phenomenon is termed conformational polymorphism . Very recently, conformational polymorphs of bisphenyl triazene and rotaxane species were reported and successfully investigated regarding the crystallization process using intra‐ and intermolecular interactions. Moreover, Okuno and coworkers (2018) reported the occurrence of conformational polymorphism on the close related 2,2′‐(2‐(prop‐2‐yn‐1‐yloxy)cyclohexa‐2,5‐diene‐1,4‐diylidene)dimalononitrile, depending on the solvent used for sample crystallization .…”

Persistence of N—H···O═C Interactions in the Crystallization Mechanisms of Trisubstituted Bis-Ureas with Bulky Substituents

“…The QTAIM analysis indicates the presence of intermolecular interactions from a bond critical point (BCP) of attachment along the path that connects two interacting atoms . The stabilization energy in each atom···atom interaction, for the proposed first nuclei of each compound, was obtained utilizing the G AI analysis ,, determined by G AI(X···Y) = (ρ BCP /Σρ BCP ) × G M1···M N , correlating QTAIM data (ρ BCP ) and the stabilization energy of the considered dimer.…”

“…The QTAIM analysis indicates the presence of intermolecular interactions from a bond critical point (BCP) of attachment along the path that connects two interacting atoms. 36 The stabilization energy in each atom•••atom interaction, for the proposed first nuclei of each compound, was obtained utilizing the G AI analysis 15,37,38…”

Varying degrees of homostructurality in a series of cocrystals of antimalarial drug 11-azaartemisinin with salicylic acids

“…In 4, there is a more substantial slippage of around 5 Å . In the spectrum of isostructurality (Salbego et al, 2019;Bombicz, 2017;Dey et al, 2016;Gelbrich & Hursthouse, 2005), these new structures are distinct and involve translational perturbation, so that 3 might be termed closely homostructural and 4 weakly homostructural with 1 and 2. The relationship of the three arrangements is shown in Fig.…”