Crystallization Mechanisms Applied to Understand the Crystal Formation of Rotaxanes

Light-responsive rotaxane-based materials: inducing motion in the solid state

Light-responsive rotaxane-based solid-state materials are ideal scaffolds in order to develop smart materials due to the properties provided by the mechanical bond, such as control over the dynamics of the components upon application of external stimuli. This perspective aims to highlight the relevance of these materials, by pointing out recent examples of photoresponsive materials prepared from a rotaxanated architecture in which motion of the counterparts and/or macroscopic motion of the interlocked materials are achieved. Although further development is needed, these materials are envisioned as privileged scaffolds which will be used for different advanced applications in the area of molecular machinery.

The role of attractive and repulsive interactions in the stabilization of ammonium salts structures

A series of ammonium salts was used to propose a step-by-step approach to obtain the stabilization energy and contact area data of supramolecular clusters in charged molecules. A new parameter was presented to assess the cluster energy efficiency.

Uncovering the origins of supramolecular similarity in a series of benzimidazole structures

Quantitative similarity indices (IX) were combined with crystallization mechanism proposals to shed more light on the origins of the supramolecular similarity between a series of benzimidazole derivative structures.

Effect of Hydrogen Bonds and π...π-interactions on the Crystallization of Phenyl-perfluorophenyl Amides: Understanding the Self-organization of a Cocrystal

A series of N-arylbenzamides containing amide group and phenyl−perfluorinated rings were used as the smallest molecules to investigate the direct influence of hydrogen bond and aromatic donor-acceptor complementarity in the...

π-Stacking Stopper-Macrocycle Stabilized Dynamically Interlocked [2]Rotaxanes

The synthesis of mechanically interlocked molecules is valuable due to their unique topologies. With π-stacking intercomponent interaction, e.g., phenanthroline and anthracene, novel [2]rotaxanes have been synthesized by dynamic imine clipping reaction. Their X-ray crystal structures indicate the π-stackings between the anthracene moiety (stopper) on the thread and the (hetero)aromatic rings at the macrocycle of the rotaxanes. Moreover, the length of glycol chains affects the extra π-stacking intercomponent interactions between the phenyl groups and the dimethoxy phenyl groups on the thread. Dynamic combinatorial library has shown at best 84% distribution of anthracene-threaded phenanthroline-based rotaxane, coinciding with the crystallography in that the additional π-stacking intercomponent interactions could increase the thermodynamic stability and selectivity of the rotaxanes.

de Oliveira JP, A. Vasconcellos MLA, Zanatta N, G. Bonacorso H, Martins MAP. Substituent effects on the crystallization mechanisms of 7-chloro-4-substituted-quinolines

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.

Supramolecular Similarity in Polymorphs: Use of Similarity Indices (IX)

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.