The present study discusses the crystalline packing formation of several [2]rotaxanes with Leigh‐type tetralactam macrocycle bearing different threads. The presence of solvent molecules in some structures are also addressed to shed some light on this matter. Additionally, the degree of similarity between supramolecular structures of rotaxanes was discussed using similarity indices. For this, new descriptors and crystallization mechanisms, which were proposed in terms of contact area and stabilization energy, were carried out to evaluate the rotaxane molecules. It was possible to observe similar general stages of crystallization dominated by the formation of 1D‐blocks and, in fewer cases, by dimers in the first stage of nucleation. The preference for the formation of 1D nuclei resides in the large contact area and complementarity involved in the large set of interactions between the rotaxanes at the earliest stages of crystallization. In this context, it was possible to propose when solvent molecules are trapped between the rotaxanes during crystal formation. Therefore, a unique example of a rotaxane whose topology favored the entrapment of water molecules between rotaxanes during the first stage of the crystallization process is presented. Crystallization mechanisms showed to be a valuable asset in the supramolecular investigation of rotaxanes in the crystalline state.

The crystallization mechanisms of a series of fourteen 7-chloro-4-substituted-quinolines were proposed based on a retrocrystallization approach using the supramolecular cluster as demarcation.

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.

This study proposes an approach with the necessary steps to answer some questions: (i) how to build a proper demarcation for the study of salts since there are two ionic...

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