Thiacalixarenes: Emergent Supramolecules in Crystal Engineering and Molecular Recognition

A consolidated review on the emergent supramolecules of thiacalixarenes in crystal engineering and molecular recognition contributed from our group is presented. Our simple synthetic method of thiacalixarenes offered improved yields of larger macrocyclic thiacalix[6/8]arenes by carefully adjusting NaOH concentration, temperature, and reaction time. In crystallographic analysis, complexes of thiacalixarenes with alkali metals and rare earth metals build up fascinating assemblies, such as dimeric formations, hetero-alkali metallic thiacalixarenes, one-dimensional ‘ladder-type’ coordination polymers, and one-dimensional hydrogen-bonded polymers. In addition, halogenated thiacalixarenes having various alkyl ethers assemble each other via three halogen interactions of halogen bonding, halogen–halogen interactions, and halogen-π interactions. Liquid–liquid extraction studies using ligand-functionalized thiacalixarene-based extractants developed for separation of precious metals from the last 10 years are discussed.