Assembly of Interlocked Superstructures with a Titanium Oxide Molecular Ring in Water

[2]Catenane, [2]rotaxane, and [2]pseudorotaxane based on a cyclic titanium oxide cluster, [Ti8O8(SO4)(16)](16-) (Ti-8), and cyclic/linear alkylammonium cations are reported. Their syntheses, structures, spectroscopy, and stability in water were studied. These molecules were synthesized from and remained intact upon redissolution in acidic water. Hence, the cluster Ti-8 is a promising metal oxide ring that can be used as an inorganic analogue of crown ether to assemble inorganic-organic hybrid mechanical interlocked supramolecular assemblies in water.