Size‐Control by Anion Templating in Mechanochemical Synthesis of Hemicucurbiturils in the Solid State

Abstract

Self-organization is one of the most intriguing phenomena of chemical matter.W hile the self-assembly of macrocycles and cages in dilute solutions has been extensively studied, it remains poorly understood in solvent-free environments.P rovided here is the first example of using anionic templates to achieve selective assembly of differently-sized macrocycles in as olvent-free system. Using acid-catalyzed synthesis of cyclohexanohemicucurbiturils as am odel, sizecontrolled, quantitative synthesis of 6-or 8-membered macrocycles by spontaneous anion-directed reorganization of mechanochemically-made oligomers in the solid state is demonstrated.

Mechanochemistry for Synthesis

“…[55] Aging reactions can be directed by templating, as was shown by Kaabel et al who combined milling and aging with chloride or perchlorate ions to make 6-or 8-membered hemicucurbituril macrocycles,r espectively ( Figure 3b). [56] Accelerated aging is also as imple,l ow-energy way to form MOFs from metal oxides.S uch syntheses are also readily templated and catalyzed, as shown by Qi et al who templated oxalate MOFs by alkylammonium salts (Figure 3c), [54] or Mottillo et al who used caffeinium salts to control ZIF synthesis. [57] In that context, the Yuan group has shown aging also enables conversion of trivalent metal oxides into MOFs.…”

“…Aging reactions can be directed by templating, as was shown by Kaabel et al. who combined milling and aging with chloride or perchlorate ions to make 6‐ or 8‐membered hemicucurbituril macrocycles, respectively (Figure b) . Accelerated aging is also a simple, low‐energy way to form MOFs from metal oxides.…”

“…[102] Theability to template solvent-free self-assembly was shown by Kaabel et al in making size-controlled hemicucurbiturils. [56] In the context of extended structures,a ldimine condensation by grinding was used by the Banerjee group to make covalent organic frameworks (COFs, Figure 10 e), [103] while Grätz et al obtained ap oly(azomethine) from terephthaldehyde and pdiaminobenzene. [104] Ther eaction was complete in minutes, giving ap roduct of lower band gap (2.18 eV) than the standard material, indicating ahigher degree of conjugation.…”

Exploring the Scope of Macrocyclic “Shoe-last” Templates in the Mechanochemical Synthesis of RHO Topology Zeolitic Imidazolate Frameworks (ZIFs)

“…More broadly, the results suggest that a wide array of small molecules may be chosen or designed to direct the topological outcome in the synthesis of ZIFs susceptible to framework polymorphism. Besides representing a step forward towards topologically-controlled synthesis of zeolitic metal-organic frameworks, the presented work is also a notable contribution to mechanochemical and mechanically-activated synthesis of complex structures, as it represents a still rare example of using templates to direct the outcome of solvent-less synthetic procedures [61].…”

Recent Advances in Mechanochemical Organic Synthesis

“…This complex could not be obtained by direct milling of MOF with BODIPY dyes [85]. Furthermore, the size of mechanochemically prepared hemicucurbituril macrocycles was effectively controlled by anion templating [86]. Pseudorotaxanes which were prepared in solution were transformed into diamide rotaxanes [2] by solvent-free reaction of amine and acyl chloride terminus forming amide stoppers [87].…”