Octanuclear aluminum(III) and iron(III) phosphonate cages encapsulating two Na(I) ions.

Hydrothermal reactions of aluminum(III) nitrate or iron(III) nitrate with N,N-dimethylaminomethane-1,1-diphosphonic acid (H(4)L) and sodium hydroxide lead to two novel isostructural octanuclear metal phosphonate cages encapsulating two Na(I) ions, namely, [Al(8)Na(2)(HL)(2)(H(2)L)(10)(H(2)O)(6)] x 20 H(2)O (1) and [Fe(8)Na(2)(HL)(2)(H(2)L)(10)(H(2)O)(6)] x 22 H(2)O (2). The molecular structure of 1 can be viewed as a three-in-one cluster, in which a central zeolite D6R SBU lookalike aluminophosphonate cage is capped by two symmetry-related aluminophosphonate tetrahedral cages above and below and such a tetrahedral cage, being composed of four zeolite S6R SBU lookalike aluminophosphonate rings, further hexadentately traps one Na(+) ion in its cavity.