Porous Molecular Capsules as Non‐Polymeric Transducers of Mechanical Forces to Mechanophores

Abstract

Mechanicalg rinding/milling can be regarded as historically the first technology for changing the properties of matter.M echanicallya ctivated molecular units (mechanophores) can be present in various structures:p olymers,m acromolecules, or smallm olecules. However,o nly polymers have been reported to effectively transduce energy to mechanophores,w hich induces breakage of covalentb onds. In this paper,asecond possibility is presented-molecular capsules as stress-sensitiveu nits. Mechanochemical encapsulation of fullerenes in cystine-based covalent capsules indi-cates that complexation takes place in the solid state, despite the fact that the capsules do not possess large enough entrance portals. By using as et of solvent-free MALDI (sf-MALDI) and solid-state NMR (ss-NMR) experiments,i th as been provent hat encapsulation proceedsduring milling and in this process hydrazones and disulfides get activated for breakage, exchange, and re-forming. The capsules are porousa nd therefore prone to collapse under solvent-free conditions and their conformational rigidity promotes the collapse by the breaking of covalent bonds.[a] Dr.

Anion-Based Self-assembly of Resorcin[4]arenes and Pyrogallol[4]arenes

“…Without Alk 4 NX being added, only P4C and R4C have detectable solubility in benzene, exhibiting patterns characteristic for ( P4C ) 6 or ( R4C ) 6 (H 2 O) 8 (Figure a,f). With positive experience in the application of mechanochemical ball milling as a method to initialize interaction between the components, − we used this method to pre-treat the samples.…”

Water-stable hydrazone-linked porous organic cages

“…To the best of our knowledge, only four hydrazonelinked organic cage structures are solved by SCXRD, and none of their cavity diameters is more than 2.5 nm. [55][56][57][58] Both indexes are much lower than those of imine-linked cages with numerous crystals characterized by SCXRD and a cavity diameter up to 4.3 nm. 59 Moreover, none of the reported hydrazone-linked organic cages has been explored as porous molecular solids for practical applications.…”

Polymer and small molecule mechanochemistry: closer than ever

“…However, not only the definition of a mechanophore has evolved in recent years but also the means to transduce mechanical energy to the mechanophores. Typically, polymers were the force transmission medium of choice, but in a recent study, Potrzebowski, Szumna, and co-workers have shown that molecular capsules can behave as stress-sensitive units [65]. The authors demonstrated the effective complexation of the covalent capsule 5 (made from resorcinarene caps connected by four dihydrazone units of ʟ-cysteine) with C 60 and C 70 fullerenes upon neat ball milling in a planetary ball mill (Figure 6).…”

“…Therefore, during ball milling, 5 gets partially disintegrated at the weakest covalent connections, enabling the access of fullerenes. As a result, besides polymeric matrices, also porous, semirigid molecules [65] and molecular anvils [66] could eventually become effective transducers of mechanical forces to mechanophores.…”