Macrocyclic host molecules can play important roles in supramolecular chemistry. They can form host–guest complexes, have uses in stimuli-responsive materials, and can be useful in building molecular machines. Naphthotubes are macrocyclic hosts that contain two curved bis(naphthalene) “clefts” that are connected to form a tube-like shape. An ether naphthotube (pictured above), for example, has an electron-rich cavity due to the presence of electron-donating alkoxynaphthalene units.
Wei Jiang, Southern University of Science and Technology, Shenzhen, China, Li-Li Wang, Liu-Pan Yang, University of South China, Hunan, and colleagues have investigated the host–guest chemistry of this ether naphthotube with different types of dicationic guests in organic media. The dicationic guests were prepared from different nucleophile end groups and a 1,6-dibromohexane linker in acetonitrile. The resulting host–guest complexes were studied using 1H NMR spectroscopy and isothermal titration calorimetry (ITC).
The team found that the macrocycle shows strong binding affinities towards different dicationic guests and a high binding selectivity that depends on the shape and electronic properties of the guests. An N-methylmorpholinium-based dication was found to be the “best” guest. The host–guest complexes were used to prepare rotaxanes by putting di-tert-butylbenzyl-based “stopper” units on the ends of the guest molecules (schematically pictured).
- Ether Naphthotube Host-guest Complexes and [2]Rotaxanes with Dications,
Li-Shuo Zheng, Song-Meng Wang, Wei Jiang, Li-Li Wang, Liu-Pan Yang,
Chem. Eur. J. 2024.
https://doi.org/10.1002/chem.202401079
