Functional Materials with Pillarene Struts

Pillar[n]arenes (pillarenes for short) are a relatively new generation of macrocyclic host compounds with rigid cylinder architectures containing several hydroquinone units that are bridged by methylene (-CH2-) at their para positions. The investigation of pillarenes has expanded from the sole domain of supramolecular chemistry to invoke immense interest among scientists striving to exploit intelligent materials or functional systems, with regard to their fascinating attributes such as symmetric structures, tailorable functionalization, and unique host-guest properties. Over the past few years, researchers have focused on the construction of prominent supramolecular architectures such as supramolecular switches, supramolecular polymers, and self-assembled amphiphilic systems on the basis of host-guest chemistry in collaboration with other noncovalent interactions. One of the most attractive characteristics of these supramolecular assemblies relies on the tunable mechanical motions via switching of the most conformationally and thermally stable structures in a dynamic and reversible manner, which could be affected by the external conditions and enable the reciprocal effect with surrounding environments. Consequently, macrocyclic arenes are the key components of stimuli-responsive supramolecular assemblies, serving as important candidates in the construction of advanced supramolecular materials, including organic functional systems and organic-inorganic hybrid systems. In this Account, we present a relatively elaborate summary of the significant and typical intelligent systems containing pillarenes and their extended versions with a focus on our own contributions to this field during the past decade. Finally, in the last section of the review, challenges and perspectives are given.