Complex-within-complex assemblages from {M([2.2.2]cryptand)(H2O)2}2+ (M = Sr, Ba) and {UO2(p-tert-butyl[3.1.3.1]homooxacalixarene-4H)}2-

The reaction between p-tert-butyl[3.1.3.1] homooxacalixarene, currently named p-tert-butyltetrahomodioxacalix[ 4] arene, LH4, and uranyl salts in the presence of [2.2.2] cryptand and the alkaline-earth metal cations Sr2+ or Ba2+ gives the complexes [{Sr[2.2.2](H2O)(2)} subset of {UO2( L)}] center dot H2O center dot 4CH(3)OH and [{Ba[2.2.2](H2O)(2)} subset of {UO2( L)}] center dot 4H(2)O center dot 4CH(3)OH, respectively. In the crystal, the uranyl ion is located in the tetra-phenoxide site of the homooxacalixarene in the cone conformation and linked to the cryptate by a water center dot center dot center dot oxo hydrogen bond. The cryptate is included in the uranyl complex cavity and the infinite chains formed through hydrogen bonds and other weak interactions are thus novel examples of complex-within-complex supramolecular assemblages. By contrast, the addition of triethylamine to the reaction mixture leads to the compound {Ba[2.2.2](H2O)(2)}{[HNEt3] subset of [UO2(L)]}(2) center dot 5H(2)O, in which the triethylammonium cation replaces the cryptate in the cavity, the cryptate simply acting as a link between two uranyl complex moieties through water center dot center dot center dot phenoxide hydrogen bonds. The assemblage [{Ba[2.2.2](H2O)(2)} subset of (LH3)](LH3) center dot 2H(2)O, including the uncomplexed anion LH3-, is also described. Analysis of the NMR spectra of the three uranyl complexes indicates that the cryptate and the [UO2(L)](2-) moieties do not specifically interact in dilute (CD3)(2)SO solution, while the supramolecular arrangement of {Ba[2.2.2](H2O)(2)}{[HNEt3] subset of [UO2( L)]}(2) center dot 5H(2)O is largely retained in halogenated solvents.