Difference of Coordination between Alkali- and Alkaline-Earth-Metal Ions to a Symmetrical α,α′,δ,δ′-Tetramethylcucurbit[6]uril

Abstract

To explore differences in coordination between alkali- and alkaline-earth-metal ions and cucurbit[n]urils, a water-soluble α,α',δ,δ'-tetramethylcucurbit[6]uril (TMeQ[6]) was used to synthesize a series of complexes and their supramolecular assemblies, based on the coordination of TMeQ[6] with alkali- and alkaline-earth-metal ions. The complexes and corresponding supramolecular assemblies were structurally characterized by single-crystal X-ray diffraction. Unlike cucurbituril (Q[6]), which formed the metal-Q[6] polymers based on the direct coordination of carbonyl oxygen atoms to the alkali-metal ions, TMeQ[6] formed metal-TMeQ[6] polymers based on the direct coordination of carbonyl oxygen atoms with the alkaline-earth-metal ions rather than the alkali-metal ions.

Assemblies of Alkaline‐Earth‐Metal Ions with o‐Tetramethyl‐Substituted Cucurbituril in the Presence of the Cadmium Tetrachloride Anion

“…Scheme 2. Experimental procedure and structure of the ortho-tetramethyl-substituted cucurbituril molecule (o-TMeQ [6]). …”

“…[9] Among these are the controlled synthetic methods, in which certain basic building blocks are introduced in the synthetic processes; for example, Day first used diether of a dimethyl-substituted glycoluril with normal glycoluril to synthesize 1,3,5-hexamethyl cucurbituril (1,3,5-HMeQ [6]). …”

“…[10] Issacs and co-workers used a series of glycoluril polymers to synthesize a series of novel partial alkyl-substituted cucurbit[n]urils. [11] Very recently, we synthesized a new building block dimer of dimethyl-substituted glycoluril, and reaction of this dimer with normal glycoluril yielded a symmetrical octamethylsubstituted cucurbituril (OMeQ [6]) as the dominant target product. [12] In the present workϪwhich used two dimers, the dimer of the normal glycoluril and the dimer of dimethyl-substituted glycolurilϪwe synthesized and isolated a new ortho-tetramethyl-substituted cucurbituril (o-TMeQ [6]) as the dominant target product (Scheme 2).…”

“…[12] In the present workϪwhich used two dimers, the dimer of the normal glycoluril and the dimer of dimethyl-substituted glycolurilϪwe synthesized and isolated a new ortho-tetramethyl-substituted cucurbituril (o-TMeQ [6]) as the dominant target product (Scheme 2). [13] Moreover, we selected this o-TMeQ [6] …”

“…Coordination assemblies have been investigated by reactions between alkaline earth cations and o-TMeQ [6] in the presence of [CdCl 4 ] 2-, a structure inducer, in HCl aqueous solution. X-…”