Redox‐Triggered Chirality Switching and Guest‐Capture/Release with a Pillar[6]arene‐Based Molecular Universal Joint

Abstract

A chiral electrochemically responsive molecular universal joint (EMUJ) was synthesized by fusing a macrocyclic pillar[6]arene (P[6]) to a ferrocene-based side ring. A single crystal of an enantiopure EMUJ was successfully obtained, which allowed, for the first time, the definitive correlation between the absolute configuration and the circular dichroism spectrum of a P[6] derivative to be determined. The self-inclusion and self-exclusion conformational change of the EMUJ led to a chiroptical inversion of the P[6] moiety, which could be manipulated by both solvents and changes in temperature. The EMUJ also displayed a unique redoxtriggered reversible in/out conformational switching, corresponding to an occupation/voidance switching of the P[6] cavity, respectively. This phenomenon is an unprecedented electrochemical manipulation of the capture and release of guest molecules by supramolecular hosts.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Stereochemical Inversion of Rim-Differentiated Pillar[5]arene Molecular Swings

“…These findings thus shed more light on the complex nature of the dynamic process of pillar[5]arene stereochemical inversion and may provide future design guidance for pillararene-based chiral sensors 20 and molecular switches and machines. 21 …”

Control of Dynamic sp3-C Stereochemistry

“…(S,S)-2. Cooling the solution to 159 K causes the barbaralane 13 C{ 1 H} NMR resonances to enter the slow exchange regime. As 159 K is only ~20 K below the observed coalescence temperature (Fig.…”

“…Chirality also arises in organic molecules by virtue of motifs other than stereogenic atoms. But while some planar chiral motifs, [11][12][13] helices, [14][15][16] and atropisomeric bonds, 3 as well as stereogenic sp 3 -nitrogen centres, [7][8][9][10] change configuration rapidly and reversibly through low-barrier processes, sp 3 -carbon centres cannot generally undergo spontaneous inversion. For example, the energy barrier to pyramidal inversion of methane is greater than its C−H bond dissociation energy.…”

“…For example, the energy barrier to pyramidal inversion of methane is greater than its C−H bond dissociation energy. 17,18 Unlike other stereogenic motifs, [11][12][13][14][15][16] therefore, sp 3 -carbon centres cannot generally adapt their configuration to surrounding chiral moieties and cannot be controllably switched by the application of external stimuli.…”

Overtemperature-protection intelligent molecular chiroptical photoswitches

“…Therefore, realizing overtemperature protection, which is vital for switching devices/power transistors, such as the stable operation of computers and devices and safety of power supplies, with a molecular device is obviously challenging. Herein, we report an overtemperature-protection function by integrating the thermo- and photoresponsive functions into one pillar[ n ]arene-based bicyclic pseudocatenanes, so-called molecular universal joints (MUJs) 30 , 35 .…”