Two new supramolecular complexes [Hg(6)As(4)](CrBr(6))Br (1) and [Hg(6)As(4)](FeBr(6))Hg(0.6) (2) have been prepared by the standard ampoule technique and their crystal structures determined. Both crystallize in the cubic space group Pa$\bar 3$ with the unit cell parameter a=12.275(1) (1) and 12.332(1) A (2), and Z=4. Their structures consist of bicompartmental, three-dimensional [Hg(6)As(4)](4+) frameworks with cavities of two different sizes occupied by guest anions of different type. The bigger cavities are filled with the octahedral MBr(6) (n-) ions (M=Cr or Fe; n=3 or 4), whereas the smaller cavities trap either Br- ions (1) or Hg(0) (2). The analysis of the host-guest contacts has allowed a classification of the octahedral guests as coordinated and the monatomic guests as clathrated. Magnetic measurements and ESR spectroscopy data have given information about the interaction between the host and guests. Band structure calculations (HF and hybrid DFT level) indicate that both 1 and 2 are non-metallic, with a band gap of approximately 1.5 eV (B3LYP), and that the interaction between the host and guests is of predominantly electrostatic character. It is shown that though the electrostatic host-guest interaction is weak it plays an important role in assembling the perfectly ordered supramolecular architectures.

Key indicatorsSingle-crystal X-ray study T = 173 K Mean (e-O) = 0.006 Å R factor = 0.044 wR factor = 0.095 Data-to-parameter ratio = 26.0For details of how these key indicators were automatically derived from the article, seeThe structure of the title compound, Cs 3 La 11 (SeO 3 ) 12 Cl 12 , consists of complex slabs of composition [La 22 (SeO 3 ) 24 ] that are stacked along the a axis and are separated by sublayers of either chloride anions or caesium chloride. All SeO 3 groups show the typical pyramidal shape. The Se-O bond distances vary from 1.672 (6) to 1.747 (6) Å .

The cover picture shows the arrangement of the 3-D [Hg 7 As 4 ] 4ϩ host framework and the AgI 3 2Ϫ guest anions in a novel supramolecular architecture [Hg 7 As 4 ](AgI 3 ) 2 , selfassembled from a heterogeneous system at high temperature. Although the hostϪguest interaction is weak, it governs both the geometry of the host framework (mercury atoms, blue; arsenic atoms, pink) and guest anions (silver atoms, red; iodine atoms, violet) and the positioning of the guest in the framework cavities. A mutual adjustment of the host and guests results is the unusual off-plane geometry of the AgI 3 2Ϫ anion. Details are discussed in the article of A. V. Shevelkov et al. on p. 1053 ff. MICROREVIEW Contents M. Vallet-Regí,* C. V. Ragel, 1029 A. J. Salinas Glasses with Medical Applications

The first compounds, Hg(7)Ag(2)P(8)X(6) (X = Br, I) and Hg(6)Ag(4)P(8)Br(6), featuring the partial isoelectronic substitution of Hg(2+) for Ag(1+) in mercury-pnicogen frameworks have been obtained and structurally characterized. The new compounds are the supramolecular assemblies built of the covalently bonded metal-pnicogen frameworks trapping guests of different complexity. The frameworks feature the perfect ordering of Hg(2+) and Ag(1+) cations and contain P(2)(4)(-) and P(6)(6)(-) phosphorus clusters. The substitution of Hg(2+) with Ag(1+) leads to the reduction in charge of the host cluster-containing cationic matrix and concomitant replacement of the monatomic X(-) guest by a lesser amount of the AgBr(3)(2)(-) anions.

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