A new class of curved, chiral polycyclic aromatic hydrocarbon emerges from the fusion of indeno[2,1-c]fluorene and quasi[8]circulene motifs. These redox-active, antiaromatic scaffolds offer great syn...

The helical chirality of a dynamic crown-ether switch can, by light- or redox-switching to a prochiral state, be erased and subsequently stereoselectively re-formed by relaxation in the presence of a...

World authority on chemistry nomenclature aims to clean up molecular machine terminology

The modulation of molecular recognition underpins numerous wide-ranging applications and has inspired the development of a myriad of switchable receptors, in particular photo- or redox-responsive hosts. Herein, we report a highly versatile three-state cation receptor family and switch system based on an overcrowded alkene strapped with crown ethers, which can be switched by both redox and light stimuli, thereby combining the advantages of both approaches. Specifically, the neutral switches can be quantitatively converted between anti- and syn-folded receptor geometries by irradiation, leading to the discovery of a significant increase or decrease in cation binding affinity, which was exploited to shuttle the pseudorotaxane-forming dibenzylammonium guest between the switchable crown ethers of slightly different sizes. Alternatively, two-electron oxidation to the orthogonal, dicationic, nonvolatile state completely turns off cation binding to the host, thereby ejecting the guest. Upon reduction, the metastable syn-folded state is first formed, which then thermally relaxes, resulting in a unique, autonomous, and cation-dependent multistate switching cascade.