Tuning the Fluorescence Through Reorientation of the Axle in Calix[6]arene‐Based Pseudorotaxanes

Abstract

This work describes a calix[6]arene‐based wheel that binds, in non‐polar media, a stilbazolium salt to yield a mixture of pseudorotaxane orientational isomers. The isomer's abundance ratio evolves with time and can be reversibly tuned by adjusting the temperature. The spectroscopic properties, and notably the emission spectrum, of the bound guest depend on its orientation inside the non‐palindromic wheel, suggesting such a system as a switch with spectroscopic readout.

Orientational isomerisation of guest molecules in equilibrium in a tubular host crystal formed via halogen and hydrogen bonding

“…3b, c and S14–S21 and Table S2†). Since structure I with V-shaped CH 2 Cl 2 and structure I′ with Λ-shaped CH 2 Cl 2 can be regarded as supramolecular orientational isomers, 27,35 we will refer to them as V - and Λ -isomers, respectively.…”

“…1c). 25–27 In these systems, we can expect the emergence of functions due to differences in properties such as symmetry and polarisation between isomers and in host–guest interactions. On the other hand, as mentioned above, there is no known example of precise control of isomerisation equilibrium by controlling the orientation of guest molecules in the host space of a crystal.…”

Heteroditopic Calix[6]arene Based Intervowen and Interlocked Molecular Devices

“…In this context, we recently demonstrated the ability of calix[6]arene 2 wheel to tune the fluorescent properties of stilbazolium axles 15 a •OTs, depending on its relative orientation inside the macrocyclic cavity (Scheme 24). [37] …”

A 4-state acid–base controlled molecular switch based on a host–guest system

“…Many examples of crown ethers [8][9][10] and cavity-based molecular hosts (i.e. cavitands: cyclodextrins, 11,12 calixarenes, [13][14][15][16][17] pillararenes, [18][19][20] resorcinarenes, [21][22][23] ExBoxes, 24 etc.) have been reported for the construction of such supramolecular switches.…”