Since their discovery in 2008, pillar[n]arenes have been a popular family of macrocyclic arene hosts due to their accessible one-step synthesis, convenient functionalization, symmetrical prism structures and perfect cavity host-guest properties. Compared with other macrocyclic hosts, the most peculiar recognition behavior of pillararenes is the strong binding affinities of pillar[5]arenes (P5As) towards neutral guests in organic media, which is unfeasible for classic crown ethers and calixarenes. The intriguing properties have found extensive applications in many fields from supramolecular chemistry to materials science. This feature article provides a detailed summary of the molecular recognition of P5As and neutral guests, where the driving forces, binding mechanisms, and binding selectivities are comprehensively discussed. Furthermore, brief highlights of research progress in the functional applications based on the neutral guest⊂P5A motifs were also discussed, including the construction of complex topological superstructures (e.g. rotaxanes, catenanes and daisy chains), supramolecular polymers, and functional materials.

Reported here is the highly efficient separation of industrially important cis-and trans-1,2-dichloroethene (cis-DCE and trans-DCE) isomers by activated crystalline 2,2',4,4'tetramethoxyl biphen[3]arene (MeBP3) materials,M eBP3a. MeBP3 can be synthesized in excellent yield (99 %), and ac yclic pentamer is also obtained when using 1,2-dichloroethane as the solvent. The structure of MeBP3 in the CH 3 CN@MeBP3 crystal displays at riangle-shape topology, forming 1D channels through window-to-windowp acking. Desolvated crystalline MeBP3 materials,M eBP3a,p referentially adsorb cis-DCE vapors over its trans isomer.MeBP3a is able to separate cis-DCE from a5 0:50 (v/v) cis/trans-isomer mixture,y ielding cis-DCE with ap urity of 96.4 %i nas ingle adsorption cycle.S ingle-crystal structures and powder X-ray diffraction patterns indicate that the uptake of cis-DCE triggers as olid-state structural transformation of MeBP3, suggesting the adaptivity of MeBP3a materials during the sorption process.M oreover,t he separation can be performed over multiple cycles without loss of separation selectivity and capacity.

The complexation and separation of industrially important cis- and trans-1,2-dichloroethene (cis- and trans-DCE) isomers using perethylated pillar[5]arene (EtP5) are described.

Catenated cages represent chemistry's challenging synthetic targets because a threedimensional assembly is necessary for their formation. Herein, a cyclic bis[2]catenane is constructed through the coordination-driven self-assembly of the interlocked bis-metallacage, by the 90°Pt(II) heteroligation of the endo-functionalized double-bridged tweezer bearing pyridyl moieties and the tetra-carboxylated linker. NMR spectrometry, X-ray crystallography and mass spectrometry confirm the formation of a cyclic bis[2]catenane with "∞"-shaped topology via a 14-component self-assembly. Particularly, reversibly responsive transformation between the bis[2]catenane and the bis-metallacage can be realized by guest exchange, concentration effect and solvent effect. This work represents a novel example of a cyclic cage-based [2]catenane oligomer.

Conformational exchanges of synthetic macrocyclic acceptors are rather fast, which is rarely studied in the absence of guests. Here, we report multiple stimuli-responsive conformational exchanges between two preexisting conformations of 2,2′,4,4′-tetramethoxyl biphen[3]arene (MeBP3) macrocycle. Structures of these two conformations are both observed in solid state, and characterized by 1H NMR, 13C NMR and 2D NMR in solution. In particular, conformational exchanges can respond to solvents, temperatures, guest binding and acid/base addition. The current system may have a role to play in the construction of molecular switches and other stimuli-responsive systems.