(CN3H6)[FeIIFeIII(SO4)3(H2O)3]: A Framework Iron Sulfate with a Mixed S = 2 and S = 5/2 Honeycomb Lattice

A new guanidinium-templated hydrated iron sulfate, [CN3H6][FeIIFeIII(SO4)3(H2O)3] (1), was prepared from strongly acidic aqueous solutions. Its crystal structure is comprised from FeIIIO6 and FeIIO3(H2O)3 octahedra linked by sulfate bridges forming a [FeIIFeII(SO4)3(H2O)3]- 3D framework with a layer-by-layer ordering of ferric and ferrous cations. The structural topology of the framework is related to the anhydrous rhombohedral mikasaite Fe2(SO4)3. The removal of part of the sulfate tetrahedra and the partial replacement of the Fe3+ cations in the [Fe3+2(SO4)3]0 framework by Fe2+ provide a negative charge and allow the incorporation of the protonated organic species in the voids. The compound 1 has been characterized by single-crystal X-ray diffraction, TG and DSC analyses, UV-vis-NIR spectroscopy, magnetic susceptibility, Mössbauer spectroscopy, IR and Raman spectroscopy, and density functional band-structure calculations. The magnetic behavior of 1 shows an interplay of FeII (S = 2) and FeIII (S = 5/2) sublattices that exhibit different types of antiferromagnetic couplings, one FeIII-FeIII (J1 ∼ 6.1 K) and two FeII-FeIII couplings (J2 ∼ 1 K, J3 ∼ 5.9 K) within corrugated honeycomb layers. These ferrimagnetic layers are coupled antiparallel to each other, resulting in an overall antiferromagnetic order below TN = 31 K.

Protonated Organic Diamines as Templates for Layered and Microporous Structures: Synthesis, Crystal Chemistry, and Structural Trends among the Compounds Formed in Aqueous Systems Transition Metal Halide or Nitrate-Diamine-Selenious Acid

Systematic studies of crystalline compounds formed in aqueous systems containing aliphatic diamines, divalent transition metal halides, and selenious acid resulted in the discovery of a large family of new complex species corresponding to several new structure types. With ethylenediamine (en), layered (enH2)[M(HSeO3)2X2] compounds are the most commonly formed species which constitute a significant contribution to the family of layered hydrogen selenites containing neutral [M(HSeO3)2] (M = Mg, Mn, Co, Ni, Cu, Zn, Cd) 2D building blocks. In contrast to some previous suggestions, piperazine (pip), as well as its homologue N-methylpiperazine, mostly give rise to quite different, sometimes more complex, structures of varied dimensionality while the (pipH2)[M(HSeO3)2X2] compounds are formed only with M = Cu and Cd. In addition, metal-, halide-, or selenium-free by-product species are observed. The SeIV can be present in a multitude of forms, including H2SeO3, HSeO3-, SeO32-, and Se2O52-, reflecting amazing adaptability to the shape of the templating cations.

Framework Uranyl Silicates: Crystal Chemistry and a New Route for the Synthesis

To date, uranyl silicates are mostly represented by minerals in nature. However, their synthetic counterparts can be used as ion exchange materials. A new approach for the synthesis of framework uranyl silicates is reported. The new compounds Rb₂[(UO₂)₂(Si₈O₁₉)](H₂O)_2.5 (1), (K,Rb)₂[(UO₂)(Si₁₀O₂₂)] (2), [Rb₃Cl][(UO₂)(Si₄O₁₀)] (3) and [Cs₃Cl][(UO₂)(Si₄O₁₀)] (4) were prepared at harsh conditions in "activated" silica tubes at 900 °C. The activation of silica was performed using 40% hydrofluoric acid and lead oxide. Crystal structures of new uranyl silicates were solved by direct methods and refined: 1 is orthorhombic, Cmce, a = 14.5795(2) Å, b = 14.2083(2) Å, c = 23.1412(4) Å, V = 4793.70(13) ų, R1 = 0.023; 2 is monoclinic, C2/m, a = 23.0027(8) Å, b = 8.0983(3) Å, c = 11.9736(4) Å, β = 90.372(3) °, V = 2230.43(14) ų, R1 = 0.034; 3 is orthorhombic, Imma, a = 15.2712(12) Å, b = 7.9647(8) Å, c = 12.4607(9) Å, V = 1515.6(2) ų, R1 = 0.035, 4 is orthorhombic, Imma, a = 15.4148(8) Å, b = 7.9229(4) Å, c = 13.0214(7) Å, V = 1590.30(14) ų, R1 = 0.020. Their framework crystal structures contain channels up to 11.62 × 10.54 Å filled by various alkali metals.

Synthesis and crystal structure of two novel polymorphs of (NaCl)[Cu(HSeO3)2]: a further contribution to the family of layered copper hydrogen selenites

Crystals of two new polymorphic forms of the known compound (NaCl)[Cu(HSeO3)2], which we term polymorphs II and III, were formed after a ca. one-year dwelling of a crystalline precipitate under mother liquor and upon crystallization in the presence of K+, respectively. Both structures belong to the “layered copper hydroselenite” family. The polymorph II is a structural analog of (KCl)[Cu(HSeO3)2] with a fully ordered Na+ site; the main difference concerns the environment of Cu2+ which is more regular in (NaCl)[Cu(HSeO3)2]-II. In contrast to some expectations, crystallization from solutions containing KCl. NaCl, CuCl2, and H2SeO3 upon evaporation does not result in formation of mixed (Na1−x K x Cl)[Cu(HSeO3)2] crystals, but rather in a separate crystallization of (KCl)[Cu(HSeO3)2] and (NaCl)[Cu(HSeO3)2]-III which exhibits a complex structure with four ordered and one disordered Na+ sites. It is possible that longer crystallization times enhance formation of ordered structures.

A contribution to the perrhenate crystal chemistry: the crystal structures of new CdTh[MoO4]3-type compounds

Singe crystals of four new A I M II[ReO4]3 perrhenates (A I = Na, M II = Pb; A I = Na, M II = Sr, Ag, K) have been prepared from the respective A I[ReO4] and M II[ReO4]2 perrhenates using melt and solution evaporation techniques. All new compounds belong to the hexagonal CdTh[MoO4]3 structure type, similar to previously known NaCa[ReO4]3. We discuss the crystal chemical relationships within this structure type and suggest existence of some more representatives involving other tetrahedral anions.

Controlled Reduction of Sn4+ in the Complex Iodide Cs2SnI6 with Metallic Gallium

Metal gallium as a low-melting solid was applied in a mixture with elemental iodine to substitute tin(IV) in a promising light-harvesting phase of Cs₂SnI₆ by a reactive sintering method. The reducing power of gallium was applied to influence the optoelectronic properties of the Cs₂SnI₆ phase via partial reduction of tin(IV) and, very likely, substitute partially Sn⁴⁺ by Ga³⁺. The reduction of Sn⁴⁺ to Sn²⁺ in the Cs₂SnI₆ phase contributes to the switching from p-type conductivity to n-type, thereby improving the total concentration and mobility of negative-charge carriers. The phase composition of the samples obtained was studied by X-ray diffraction (XRD) and ¹¹⁹Sn Mössbauer spectroscopy (MS). It is shown that the excess of metal gallium in a reaction melt leads to the two-phase product containing Cs₂SnI₆ with Sn⁴⁺ and β-CsSnI₃ with Sn²⁺. UV-visible absorption spectroscopy shows a high absorption coefficient of the composite material.

Ag4B7O12X (X = Cl, Br, I) Heptaborate Family: Comprehensive Crystal Chemistry, Thermal Stability Trends, Topology, and Vibrational Anharmonicity

Using glass crystallization and solid-state techniques, we were able to complete the family of salt-inclusion silver halide borates, Ag₄B₇O₁₂X, by the X = Cl and I members. The new compounds are characterized by differential scanning calorimetry, single-crystal and high-temperature powder X-ray diffraction, optical spectroscopy, and density functional theory calculations. In all structures, the silver atoms exhibit strong anharmonicity of thermal vibrations, which could be modeled using Gram-Charlier expansion, and its asymmetry was characterized by the skewness vector. The topology of the silver halide and borate sublattices has been analyzed separately for the first time. Along the I → Br → Cl series, we observe a decrease of the melting point and configuration entropy and an increase of thermal expansion and its anisotropy and thermal vibration anharmonicity, which indicates decreasing stability.

Exploring new belousovite-related zinc and cadmium alkali sulfate halides: synthesis and structural variability

Fourteen new belousovite-related compounds, AZn(TO₄)X (A = K, Rb, Cs, Tl, NH₄; T = S, Se; X = Cl, Br, I) have been prepared via melt and evaporation techniques by reacting AX and ZnTO₄ either at high temperatures or in hot aqueous solutions. They adopt the layered structure of the belousovite archetype, and constitute a morphotropic series. The apophyllite-type layers in these structures undergo different corrugations, most pronounced in the case of CsZn(SO₄)I. In addition, during the study two species unrelated to belousovite, namely Na₄Zn(SO₄)₂Cl₂ and Cs₂Cd₃(SO₄)₄, were found with framework crystal structures having different topology and belonging to new structure types.

Where the extraordinaries meet: a cascade of isosymmetrical superionic phase transitions and negative thermal expansion in a novel silver salt-inclusion borate halide

A new silver iodide borate, Ag3B6O10I, is presented as a promising solid-state electrolyte with a δ ↔ γ ↔ β ↔ α cascade of the isosymmetric superionic phase transitions.

Molecular inorganic polymers: synthesis and crystal structures of KCl72H2SeO3 and CsCl7H2SeO3

KCl72H2SeO3 and CsCl7H2SeO3 have been synthesized using solution evaporation methods from aqueous solution. Both compounds are monoclinic (P2/n and P21/c) and demonstrate new structure types. One symmetrically unique SeO(OH)2 molecule is present in each structure. SeO(OH)2 molecules via strong hydrogen bonds form chains in KCl72H2SeO3 and layers in ?sCl7H2SeO3. The structures of KCl72H2SeO3 and CsCl7H2SeO3 can be described as consisting of ionic KCl chains and CsCl layers incorporated into the covalent- and hydrogen-bonded H2SeO3 matrix. To the best of our knowledge, the cases when selenious acid acts as a contributor to the molecular building blocks of salt-inclusion structures are not known to date.

Layered calcium hydrogen selenite chlorides Ca(HSeO3)Cl and Ca(HSeO3)Cl(H2O), the first halides obtained in СaCl2–H2SeO3–H2O system

Synthesis, crystal structures and IR spectra of the first representatives of calcium hydrogen selenite halides are reported. Colourless prismatic crystals of calcium hydrogen selenite chloride Ca(HSeO3)Cl and corresponding hydrated analogue Ca(HSeO3)Cl(H2O) were produced upon evaporation of aqueous solutions. Ca(HSeO3)Cl is monoclinic, P21/c, a = 7.0031(11) Å, b = 7.7336(12) Å, c = 8.5024(13) Å, β = 109.889(3)°, V = 433.02(12) Å3, R 1 = 0.039. Ca(HSeO3)Cl(H2O) is orthorhombic, Pbca, a = 6.222(4) Å, b = 10.413(7) Å, c = 16.875(10) Å, V = 1093.3 (12) Å3, R 1 = 0.041. Ca(HSeO3)Cl and Ca(HSeO3)Cl(H2O) represent new structure types. In both structures, Ca2+ cations adopt mixed-ligand environments formed by oxygen atoms of hydrogen selenite anions (and water molecules for Ca(HSeO3)Cl(H2O)) and chloride ions. Both structures are layered. The crystal structure of Ca(HSeO3)Cl(H2O) demonstrates a rare phenomenon of hydrogen-bonded assembly of water and chloride in the interlayer space.

Synthesis, electronic structure and physical properties of two new layered compounds, EuFAgSe and EuFAg1-δTe, featuring the active redox pair Eu2+/Ag. Dalton Trans 2020;49:7426-7435. [PMID: 32432284 DOI: 10.1039/d0dt01504k]

Systematic studies of the ZrCuSiAs (also LaOAgS or 1111) structure type resulted in the synthesis of two new fluoride chalcogenides, EuFAgSe and EuFAg1-δTe, whereas their sulfide analog, EuFAgS, could not be obtained. Both new compounds are tetragonal, P4/nmm, with cell parameters a = 4.1542(1) Å, c = 9.2182(1) Å for the selenide and a = 4.3255(1) Å, c = 9.5486(1) Å for the telluride. Rietveld refinement reveals a significant silver deficiency in the telluride (δ = 0.05), while the selenide is nearly stoichiometric. Both compounds are semiconductors as shown by diffuse reflectance spectroscopy and confirmed by density-functional calculations of the band structure. Magnetism of both compounds is predominantly driven by Eu2+, as indicated by magnetic susceptibility measurements and corroborated by 151Eu Mössbauer spectroscopy. EuFAg1-δTe and EuFAgSe are paramagnetic down to 1.8 K.

EuNi2P4, the first magnetic unconventional clathrate prepared via a mechanochemically assisted route

The first magnetic unconventional clathrate EuNi₂P₄ has been prepared and its thermodynamic properties have been investigated.

Li2(Se2O5)(H2O)1.5·CuCl2, a salt-inclusion diselenite structurally based on tetranuclear Li4 complexes

A new lithium copper diselenite chloride hydrate, Li₂Se₂O₅(H₂O)_1.5·CuCl₂, was prepared from aqueous solution.

Copper hydroselenite nitrates (A +NO3) n [Cu(HSeO3)2] (A=Rb+, Cs+ and Tl+, n=1, 2) related to Ruddlesden – Popper phases

Three new layered copper hydrogen selenite nitrates, (ANO3)[Cu(HSeO3)2] (A = Cs, and Tl), and (RbNO3)2[Cu(HSeO3)2] have been prepared via isothermal evaporation of concentrated nitric acid solutions. The Tl and Cs compounds adopt a motif related to previously known (NH4Cl)[Cu(HSeO3)2]; the structure of the Rb compound represents a new structure type. The structures of (ANO3)[Cu(HSeO3)2] (A = Cs, Tl), (RbNO3)2[Cu(HSeO3)2], and (NH4NO3)3[Cu(HSeO3)2] form a unique homological series distantly related to Ruddlesden – Popper series of layered perovskites.

Influence of the alkali cation size on the Cu2+ coordination environments in (AX)[Cu(HSeO3)2] (A=Na, K, NH4, Rb, Cs; X=Cl, Br) layered copper hydrogen selenite halides

Using solution evaporation techniques, we succeeded in preparation of new members essentially extending the layered copper hydrogen selenite family, (AX)[Cu(HSeO3)2] with A = Na, K, Rb, Cs, and NH4, and X = Cl and Br. Bromides and chlorides are isostructural in the family of described new compounds crystallizing in three different structure types. (NaX)[Cu(HSeO3)2] and (KX)[Cu(HSeO3)2] (X = Cl, Br) are monoclinic, whereas (AX)[Cu(HSeO3)2] (A = NH4, Rb, Cs; X = Cl, Br) are orthorhombic. Upon the enlargement of the A + ionic radii inserted in the interlayer between the neighboring [Cu(HSeO3)2] slabs, the effective distance is increasing and results in essential elongation of the apical Cu-X (X = Cl, Br) distances. Three different types of CuO4 X n (n = 0–2) polyhedra are formed. The observed trend is an interesting example of the chemical tuning of the Cu2+ coordination environments.

Synthesis, crystal and electronic structures of Pt-rich phosphides EuPt3P and EuPt6P2

Two new ternary Pt-rich phosphides, EuPt6P2 and EuPt3P, have been prepared via a two-step solid state reaction. Their crystal structures have been determined from powder XRD data. EuPt6P2 is isostructural to SrPt6P2 (cubic, Pa3[combining macron], a = 8.4603(1) Å); its crystal structure comprises corner-sharing Pt6P trigonal prisms hosting Eu2+ cations in the cuboctahedral voids of the framework. EuPt3P is isostructural to the SrPt3P anti-perovskite (P4/nmm, a = 5.7452(1) Å and c = 5.4212(1) Å). Magnetization measurements reveal the magnetic response caused by the Eu2+(4f7) cations. EuPt6P2 is paramagnetic exhibiting no phase transitions down to 1.8 K, whereas EuPt3P orders ferromagnetically below 19 K. Similar to SrPt6P2 and SrPt3P, the new compounds are metallic with states near the Fermi level predominantly formed by the 5d orbitals of Pt.

Topological analysis of the layered uranyl compounds bearing slabs with UO2:TO4 ratio of 2:3

Nine new templated uranyl sulfates and selenates, [(H9O4)2(H2O)][(UO2)2(SO4)3(H2O)2] (H9US), [(C5H7 NO)2(H2O)][(UO2)2(SeO4)3(H2O)2](H2O) (OUSe), [C6H6N3][H5O2] [(UO2)2(SeO4)3(H2O)] (BH5USe), [C6H6N3][H7O3][(UO2)2(SO4)3 (H2O)](H2O) (BH7US), [C6H16N][H5O2][(UO2)2(SeO4)3(H2O)] (TeH5USe), [C6H18N2][(UO2)2(SO4)3(H2O)] (TmUS), [H5O2]2 [(UO2)2(SeO4)3(H2O)](H2O) (H5USe-1), [H5O2]2[(UO2)2(SeO4)3 (H2O)2](H2O)9 (H5USe-2), and [C4H14N2][(UO2)2(SeO4)3(H2O)](H2O) (DmUSe) have been prepared by isothermal evaporation of aqueous solutions containing extra sulfuric or selenic acid. Their crystal structures can be considered as organo-inorganic hybrids constructed of alternating [(UO2)2 (TO4)3(H2O) n ]2− slabs (T = Se6+, S6+, n = 1, 2) and layers containing templating organic moieties and/or hydronium ions and water molecules. The organic and inorganic parts of the structures are linked by multiple hydrogen bonds. Besides structure description, we offer topological analysis of the inorganic fragments with UO2:TO4 ratio of 2:3 as modular units resulting from self-assembly of fundamental chains formed by [(UO2)2(TO4)2] tetramers and TO4 tetrahedra.

Effect of solution acidity on the structure of amino acid-bearing uranyl compounds

A series of uranyl sulfates and selenates templated by protonated forms of amino acids (glycine, α- and β-alanine, threonine, nicotinic, and isonicotinic acid) has been prepared via isothermal evaporation of strongly acidic solutions. Their structures have been refined by the direct methods and can be classified as inorganic [(UO2)m(TO4)n (H2O)k] (T=S6+, Se6+) moieties combined with the protonated amino acid cations, water molecules and hydronium ions. Their overall motifs demonstrate common features with related structures templated by organic amines. The role of carboxylic acid groups depends on the nature of the corresponding amino acid. They can either link two protonated organic moieties into dimers, or contribute to hydrogen bonding between organic and inorganic parts of the structure. The ammonium ends of the amino acid cations form strong directional bonds to the oxygens of the uranyl and TO4 anions.

Layered Compounds BaFMgPn (Pn = P, As, Sb, and Bi), Transition-Metal-Free Representatives of the 1111 Structure Type

Four new transition metal-free pnictide representatives of the LaOAgS structure type were predicted by DFT calculations and found in the BaFMgPn (Pn = P, As, Sb and Bi) family. The compounds adopt the tetragonal space group P4 /nmm with the unit cell parameters a/ c 4.3097(1) Å/9.5032(1) Å, 4.3855(1) Å/9.5918(1) Å, 4.5733(1) Å/9.8184(1) Å, and 4.6359(1) Å/9.8599(1) Å, respectively. According to the DFT calculations, these new compounds are semiconductors with band gaps steadily decreasing from Pn = P ( ca. 2 eV) to Pn = Bi ( ca. 1 eV). The corresponding strontium fluoride and rare-earth oxide analogs are unlikely to exist and have not been observed yet. The trends of the stability within 1111 and structurally and/or chemically related compounds based on a combined consideration of geometry and DFT calculations are discussed.

Structural, thermal, and IR studies of β-[Nd2O2](CrO4), an unexpected analog of a slag phase [Ba2F2](S6+O3S2−)

A family of Ln 2CrO6 (Ln=Pr, Nd, Sm–Tb) compounds has been re-investigated using powder X-ray diffraction and IR spectroscopy. The structure of β-Nd2CrO6≡β-[Nd2O2](CrO4) is similar to that of the slag compound [Ba2F2](S6+O3S2−) in that it exhibits a disordered arrangement of (CrO4)2− anions between [Nd2O2]2+ litharge-type blocks. Its structural architecture is also related to other layered α- and γ-[Ln 2O2](AO4) species (A=S, Cr, Mo), showing various orientations of the tetrahedral anions within the interlayer space. Size relationships between the incorporated tetrahedral anions and formation of different structure types (denoted as M1-, M2- and T-type) are reviewed. The possible existence of new compounds which are isostructural with, or structurally related to, β-[Nd2O2](CrO4) and bearing other transition metal-centred tetrahedral anions are discussed.

Structural and Thermodynamic Stability of the "1111" Structure Type: A Case Study of the EuFZnPn Series

Two new compounds with the LaOAgS structure, EuFZnAs (1) and EuFZnSb (2), were obtained via solid state reaction. Both compounds are tetragonal (P4/nmm) with the cell parameters a = 4.1000(1) Å and c = 9.0811(1) Å for 1 and a = 4.2852(1)Å and c = 9.4238(1)Å for 2. The absence of their phosphide analog can be explained based on crystal chemical considerations as well as on quantum-chemical estimates of their thermodynamic stability with respect to EuF₂ and EuZn₂Pn₂. The magnetic response of 1 and 2 is ascribed to the presence of Eu²⁺ ions. Both compounds are paramagnetic down to low temperatures, where they order antiferromagnetically at ∼5 K and ∼3 K, respectively. They are narrow-gap semiconductors, and EuFZnSb demonstrates a relatively high value of the Seebeck coefficient.

Synthesis and cation distribution in the new bismuth oxyhalides with the Sillén–Aurivillius intergrowth structures

Extensive synthetic and structural exploration of a new family of Sillen–Aurivillius intergrowth bismuth oxyhalides reveals clear size preferences for the alkaline earth cations and suggest a new stability criterion for complex intergrowth structures.

Theoretical DFT Study of Fragmentation and Association of Heme and Hemin

The electronic and geometric structures, energy stability, and normal vibrational frequencies of heme, hemine, and their stepwise fragmentation products (with successive loss of two carboxymethyl, four methyl, and two vinyl peripheral groups) in the states with different multiplicity were calculated using the density functional theory (the B3LYP method) with several basis sets. At the same level, the structure and stability of neutral and positively charged dimers of the ferri- and ferroporphyrines were also computed. The computational results are compared with available experimental data. The trends in the behavior of these properties of heme and hemin are analyzed upon the stepwise fragmentation and association and with a change in the multiplicity and external charge. The structure and energetic stability of complexes of the species with molecular oxygen are discussed.

Theoretical study of icosahedral closo-borane, -alane, and -gallane dianions (A(12)H(12)(2-); A = B, Al, Ga) with endohedral noble gas atoms (Ng = He, Ne, Ar, and Kr) and their lithium salts (Li[Ng@A(12)H(12)](-) and Li(2)[Ng@A(12)H(12)])

Geometries, energies, vibrational frequencies, and magnetic properties have been computed at the B3LYP level with the 6-31G and 6-311+G basis sets for a family of endohedral closo-boranes, -alanes, and -gallanes Ng@A(12)H(12)(2-) with noble gas atoms (Ng) located in the centers of icosahedral [B(12)], [Al(12)], and [Ga(12)] clusters. The endohedral structures of most of the systems are minima lying above separated Ng + A(12)H(12)(2-) by 166 (He@B(12)H(12)(2-)) and 403 (Ne@B(12)H(12)(2-)) kcal/mol for boranes; 29 (He@Al(12)H(12)(2-)), 63 (Ne@Al(12)H(12)(2-)), 154 (Ar@Al(12)H(12)(2-)), and 189 (Kr@Al(12)H(12)(2-)) kcal/mol for alanes; and 39 (He@Ga(12)H(12)(2-)), 71 (Ne@Ga(12)H(12)(2-)), and 213 (Ar@Ga(12)H(12)(2-)) kcal/mol for gallanes. Three types of transition states are found for the exit of Ng from a cage: via an edge (TS-1), through a face (TS-2), and via a more extensive deformation through a pentagonal cage "neck" (TS-3). The most favorable exit path depends on the rigidity of the cage, the exothermicity of the dissociation, and the relationship between the size of the internal cavity of the cage and the Ng atomic radius. Ng exit via TS-3 is preferred for He@Al(12)H(12)(2-), Ne@Al(12)H(12)(2-), He@Ga(12)H(12)(2-), Ne@Ga(12)H(12)(2-), Ar@Al(12)H(12)(2), and Kr@Al(12)H(12)(2-). Helium exits via a cage edge (TS-1) for He@B(12)H(12)(2-), while for Ne@B(12)H(12)(2-) the neon exits via a triangular face (TS-2). Exit barriers (H(exit)(double dagger)) are high enough (30-60 kcal/mol) for all helium clusters and for Ne@Al(12)H(12)(2-) and Ne@Ga(12)H(12)(2-) to ensure the kinetic stability of these systems. The barriers for Ar@Al(12)H(12)(2-) and Kr@Al(12)H(12)(2-) decrease to 10-15 kcal/mol, while Ne@B(12)H(12)(2-) has a very low exit barrier and is not expected to be stable kinetically. There is a linear dependence of Ng@A(12)H(12)(2-) cage size on the Ng atomic radii; that is, the heavier Ng atoms "bulge" the cages. Nucleus independent chemical shifts (NICS) indicate that all three A(12)H(12)(2-) anions are aromatic but the alanes are the least so. A face- or edge-coordinated external Li(+) cation has a moderate effect on the structure and vibrational and magnetic properties of the helium-containing clusters, i.e., Li[He@A(12)H(12)](-). In contrast, for systems with very large exothermicities of Ng exit, Li(+) complexation promotes their dissociation. Thus, the internal atom Ne exits from the cage of Li[Ne@B(12)H(12)](-) and the salt dissociates into Ne + LiB(12)H(12)(-) without barrier. Systems with two Li(+) ions located initially above opposite cage faces (Li(2)[Ng@A(12)H(12)]) undergo complex intramolecular rearrangements leading to destruction of the icosahedral closo structures.