Pseudo[n]-pillar[5]arenes: Synthesis, Structures, and Host–Guest Binding Properties

Abstract

[1 n ]Paracyclophane has been known for nearly 40 years, but its derivatives and properties are understudied in comparison to those of other macrocyclic compounds. By the modification of pillar[5]arene, we successfully obtained five electron-rich pentagonal macrocycles (pseudo[n]-pillar[5]arenes, n = 1–4) with the decrease of substituted phenylenes one after another, achieving the partial derivatization of [15]paracyclophane skeleton at its phenylene sites. Pseudo[n]-pillar[5]arenes (P[n]P[5]s) served as a kind of macrocyclic host to form complexes with various guests, such as dinitriles, dihaloalkanes, and imidazolium salt, in a 1:1 host–guest stoichiometric ratio. The binding constants with the guest gradually reduce along the decrease of substituted phenylene segments from host P[1]P[5] to P[4]P[5]. It is worthy to note that P[n]P[5]s can adjust their conformations to the “pillar-like” shape effectively when binding with succinonitrile in the solid state.

Synergizing supramolecular chemistry and reverse saturable absorption: exploring pillar[5]arene with metal-complexed ligands

“…Their synthesis generally involves the cyclooligomerization of para-substituted hydroquinones and formaldehyde. Research shows that these compounds have a wide range of applications, especially in the field of supramolecular chemistry, such as in the development of polymeric systems for biomedical applications, 1 host-guest binding properties, 2 and adsorption and separation processes. 3,4 Additionally, they're used in catalysis and sensing applications, 5 and have been modified for specific functions like targeted drug delivery 6 , imaging and utilized in Xenon based MRI applications.…”