Solvent‐Controlled Quadruple Catenation of Giant Chiral [8+12] Salicylimine Cubes Driven by Weak Hydrogen Bonding

Abstract

Mechanically interlocked structures are fascinating synthetic targets and the topological complexity achieved through catenation offers numerous possibilities for the construction of new molecules with exciting properties. In the structural space of catenated organic cage molecules, only few examples have been realized so far, and control over the catenation process in solution is still barely achieved. Herein, we describe the formation of a quadruply interlocked catenane of giant chiral [8+12] salicylimine cubes. The formation could be controlled by the choice of solvent used in the reaction. The interlocked structure was unambiguously characterized by single crystal X‐ray diffraction and weak hydrogen bonding was identified as a central driving force for the catenation. Furthermore, scrambling experiments using partially deuterated cages were performed, revealing that the catenane formation occurs through mechanical interlocking of preformed single cages.

Assembly of Multi-Dimensional Molecular Networks through Self-Complementary Halogen-Bonded Tectons

“… − With structural and energetic similarities to hydrogen bonding, the strength of halogen bonding can be intuitively tuned (e.g., −1.1 to −7.81 kcal/mol), , and the interaction with the Lewis base is antipodal to the covalent bond with the electron-withdrawing group, forming near-ideal linear interactions (Figure a). Indeed, significant success has been had in applying halogen bonding analogously to hydrogen bonding in the cornerstone supramolecular subfields of catalysis, molecular machines, ion-sensing, and, particularly, crystal engineering (Figure b). − However, despite almost 20 years of crystal engineering efforts, halogen bonding remains far behind hydrogen bonding in at least one highly desired area, the assembly of multi-dimensional and low-density crystalline networks.…”

Systematic exploration of accessible topologies of cage molecules via minimalistic models

“…10 Indeed, under these conditions, building block geometry and stoichiometry can predict topological outcomes, which infer geometrical properties. But researchers are targeting more complex structures 11,12 (towards improved tunability) through flexible, unsymmetrical, or mixed components. 13–16 Therefore, the degrees of freedom to be considered will only grow, making the use of existing design rules for cages less viable.…”

Formation Process of SiF6@Cu2L4 Chiral Cage Pairs in a Glass Vessel: Catechol Oxidation Catalysis and Chiral Recognition

“…Notable research results on chiral coordination cages for recognition of targeting chiral molecules have been reported since enantio-recognition became a subject of great interest in various chiral fields such as pharmaceuticals, pesticides, cosmetics, environmental pollutants, bioactive food products, and catalysis. − A number of different chiral coordination cages have been synthesized via a stereogenic center, atropisomerism, or noncovalent interactions for task-specific chiral applications. − Both the confined space and interaction site of chiral cage hosts are pivotal to the feasibility of chiral recognitions, and thus, such factors should be considered in constructing new chiral cages. In addition, (counter)­anions significantly affect specific functions including catalysis of coordination cages, owing to a variety of features such as negative charge, size, geometry, solvent effects, and sensitive pH dependence. − Copper­(II) catalysis oxidation of catechols into the corresponding o -quinones along with the reduction of oxygen to water is an important process in the field of biomimetic oxidases. − Catechol oxidation catalysis using copper catalysts is sensitive to the nature of coligands, ligands, the Cu···Cu distance, electrochemical potentials, and pH change. − On the other hand, dihydroxyphenylalanine (DOPA) has been regarded as an important chiral molecule in the fields of medicine, biology, and marine adhesion. − l -DOPA, for instance, is known to play a crucial role at the clinical level and in neurochemistry with respect to Parkinson’s disease, in contrast to its chiral isomer, inactive and toxic d -DOPA. , Previously, our group achieved enantioselective electrochemical recognition of various amino acids. − In this context, the central objective of the present study was efficient construction of a pair of chiral coordination cages, catechol oxidation, and enantio-recognition of l - and d -DOPA. Herein, we report chiral Cu 2 L 4 cage pairs obtained by the self-assembly of CuX 2 with a newly designed pair of s,r - or r,s -chiral bidentate ligands.…”