What is the most significant result of this study?We have proposed an ew strategy,al igand exchange strategy,t o control the response speeds of the helicity induction and inversion of helical complexes. Whereas there have already been an umber of reports on responsive helicity induction and inversion, methods to control the response speeds have not been established. In this study,w ef ocused on the reactivity of saloph-cobalt(III) complexes, which allows the exchange of the axial amine ligands on the timescale of several tens of minutes. We can control the response speeds by using different combinations of achiral and/or chiral amines as the initial and entering ligands.

Significance We first observed a transient chirality inversion on a simple unimolecular platform during the racemization of a chiral helical complex [LCo 3 A 6 ] 3+ , i.e., the helicity changed from P -rich (right-handed) to M -rich (left-handed), which then racemized to a P / M equimolar mixture in spite of the absence of a reagent that could induce the M helix. This transient chirality inversion was observed only in the forward reaction, whereas the reverse reaction showed a simple monotonic change with an induction time. Consequently, the M helicity appeared only in the forward reaction. These forward and reverse reactions constitute a hysteretic cycle. Compounds showing such unique time responses would be useful for developing time-programmable switchable materials that can control the physical/chemical properties in a time-dependent manner.

A ligand exchange strategy was successfully utilized for tuning the response speeds of helicity induction and inversion of a metal‐containing helical structure. The helicity changes were driven by the exchange of six axial amine ligands that are introduced into the three Co3+ centers in the metallocryptands, and the response speeds were efficiently controlled by using different combinations of the starting and entering amine ligands. More information can be found in the Communication by Shigehisa Akine et al. on page 2962.

Invited for the cover of this issue is the group of Shigehisa Akine at the Kanazawa University and the University of Tsukuba. The image depicts a scene with a triple helical molecule with a right‐handed helicity going into the world of mirror images upon the ligand exchange of the initial amines (orange‐colored) with the entering amines (green‐colored). Read the full text of the article at https://doi.org/10.1002/chem.201805799.