Peculiar All‐Metal σ‐Aromaticity of the [Au2Sb16]4− Anion in the Solid State

Gas‐phase clusters are deemed to be σ‐aromatic when they satisfy the 4n+2 rule of aromaticity for delocalized σ electrons and fulfill other requirements known for aromatic systems. While the range of n values was shown to be quite broad when applied to short‐lived clusters found in molecular‐beam experiments, stability of all‐metal cluster‐like fragments isolated in condensed phase was previously shown to be mainly ascribed to two electrons (n=0). In this work, the applicability of this concept is extended towards solid‐state compounds by demonstrating a unique example of a storable compound, which was isolated as a stable [K([2.2.2]crypt)]⁺ salt, featuring a [Au₂Sb₁₆]^4? cluster core possessing two all‐metal aromatic AuSb₄ fragments with six delocalized σ electrons each (n=1). This discovery pushes the boundaries of the original idea of Kekulé and firmly establishes the usefulness of the σ‐aromaticity concept as a general idea for both small clusters and solid‐state compounds.     

Stability,Infrared Spectra and Electronic Structures of (ZrO2)n(n=3-6)Clusters:DFT Study

The stability, infrared spectra and electronic structures of (ZrO₂)_n (n=3–6) clusters have been investigated by using density‐functional theory (DFT) at B3LYP/6‐31G* level. The lowest‐energy structures have been recognized by considering a number of structural isomers for each cluster size. It is found that the lowest‐energy (ZrO₂)₅ cluster is the most stable among the (ZrO₂)_n (n=3–6) clusters. The vibration spectra of Zr? O stretching motion from terminal oxygen atom locate between 900 and 1000 cm^?1, and the vibrational band of Zr? O? Zr? O four member ring is obtained at 600–700 cm^?1, which are in good agreement with the experimental results. Mulliken populations and NBO charges of (ZrO₂)_n clusters indicate that the charge transfers occur between 4d orbital of Zr atoms and 2p orbital of O atoms. HOMO‐LUMO gaps illustrate that chemical stabilities of the lowest‐energy (ZrO₂)_n (n=3–6) clusters display an even‐odd alternating pattern with increasing cluster size.     

Evaporation of tetramers in Sb4n clusters and conditions for the formation of Sb2n+1 clusters

Antimony clusters are produced by the inert gas condensation technique. They are found to be built from Sb₄ units. The fragmentation by evaporation of Sb₄ units is studied as a function of the excess energy in the cluster. By this way the binding energy of the Sb₄ units in the cluster is found to be about 1.5 eV, well below the binding energy of a Sb atom in the bulk and in Sb₄(?3eV). The evolution of ionization potentials of Sb_4n clusters confirms that their structure is probably non metallic. Finally the possible metastable character of this Sb_4n structure is discussed.     

High Nuclearity Antimonato‐Polyoxovanadate Cluster {V15Sb6O42} as a Synthon for the Solvothermal in situ Generation of α‐ and β‐{V14Sb8O42} Isomers

New heteroatom polyoxovanadates (POVs) were synthesized by applying a water‐soluble high‐nuclearity cluster as new synthon. The [V₁₅Sb₆O₄₂]^6? cluster shell exhibiting D₃ symmetry was in situ transformed into completely different cluster shells, namely, the α‐[V₁₄Sb₈O₄₂]^4? isomer with D_2d and the β‐[V₁₄Sb₈O₄₂]^4? isomer with D_2h symmetry. The solvothermal reaction of {Ni(en)₃}₃[V₁₅Sb₆O₄₂(H₂O)_x] ? 15 H₂O (x=0 or 1; en=ethylenediamine) in water led to the crystallization of [{Ni(en)₂}₂V₁₄Sb₈O₄₂] ? 5.5 H₂O containing the β‐isomer. The addition of [Ni(phen)₃](ClO₄)₂ ? 0.5 H₂O (phen=1,10‐phenanthroline) to the reaction slurry gave the new compound {Ni(phen)₃}₂[V₁₄Sb₈O₄₂] ? phen ? 12 H₂O with the α‐isomer. Both transformation reactions are complex due the change of symmetry, the chemical composition, and rearrangement of the VO₅ square pyramids and Sb₂O₅ handle‐like moieties.     

{[CuSn5Sb3]2−}2: A Dimer of Inhomogeneous Superatoms

Reaction of the binary Zintl anion (Sn₂Sb₂)^2? with the β‐diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C₆H₃ⁱPr₂‐2,6)C(Me))₂CH]^?) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn₅Sb₃]^2?}₂ ( 1 ) as its [K(crypt‐222)]⁺ salt. The chemical formulation of 1 is supported by energy‐dispersive X‐ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic “[CuSn₅Sb₃]^2?” cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non‐bonding Cu???Cu distance.     

Ab initio investigation of water clusters (H2O)n (n = 2–34)

Various properties of typical structures of water clusters in the n = 2–34 size regime with the change of cluster size have been systematically explored. Full optimizations are carried out for the structures presented in this article at the Hartree–Fock (HF) level using the 6‐31G(d) basis set by taking into account the positions of all atoms within the cluster. The influence of the HF level on the results has been reflected by the comparison between the binding energies of (H₂O)_n (n = 2–6, 8, 11, 13, 20) calculated at the HF level and those obtained from high‐level ab initio calculations at the second‐order Møller–Plesset (MP2) perturbation theory and the coupled cluster method including singles and doubles with perturbative triples (CCSD(T)) levels. HF is inaccurate when compared with MP2 and CCSD(T), but it is more practical and allows us to study larger systems. The computed properties characterizing water clusters (H₂O)_n (n = 2–34) include optimal structures, structural parameters, binding energies, hydrogen bonds, charge distributions, dipole moments, and so on. When the cluster size increases, trends of the above various properties have been presented to provide important reference for understanding and describing the nature of the hydrogen bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Optimization of bimetallic Cu–Au and Ag–Au clusters by using a modified adaptive immune optimization algorithm

A modified adaptive immune optimization algorithm (AIOA) is designed for optimization of Cu–Au and Ag–Au bimetallic clusters with Gupta potential. Compared with homoatom clusters, there are homotopic isomers in bimetallic cluster, so atom exchange operation is presented in the modified AIOA. The efficiency of the algorithm is tested by optimization of Cu_nAu_38‐n (0 ≤ n ≤ 38). Results show that all the structures with the putative global minimal energies are successfully located. In the optimization of Ag_nAu_55‐n (0 ≤ n ≤ 55) bimetallic clusters, all the structures with the reported minimal energies are obtained, and 36 structures with even lower potential energies are found. On the other hand, with the optimized structures of Cu_nAu_55‐n, it is shown that all 55‐atom Cu–Au bimetallic clusters are Mackay icosahedra except for Au₅₅, which is a face‐centered cubic (fcc)‐like structure; Cu₅₅, Cu₁₂Au₄₃, and Cu₁Au₅₄ have two‐shell Mackay icosahedral geometries with I_h point group symmetry. © 2009 Wiley Periodicals, Inc. J Comput Chem 2009     

Studies on the Magnetic Ground State of a Spin Möbius Strip

Here we report the synthesis, structure and detailed characterisation of three n‐membered oxovanadium rings, Na_n[(V=O)_nNa_n(H₂O)_n(α, β, or γ‐CD)₂]?m H₂O (n=6, 7, or 8), prepared by the reactions of (V=O)SO₄?x H₂O with α, β, or γ‐cyclodextrins (CDs) and NaOH in water. Their alternating heterometallic vanadium/sodium cyclic core structures were sandwiched between two CD moieties such that O‐Na‐O groups separated the neighbouring vanadyl ions. Antiferromagnetic interactions between the S=1/2 vanadyl ions led to S=0 ground states for the even‐membered rings, but to two quasi‐degenerate S=1/2 states for the spin‐frustrated heptanuclear cluster.     

A Series of Novel Organically Templated Germanium Antimony Sulfides

A series of novel organically templated germanium antimony sulfides have been solvothermally synthesized and structurally, thermally, and optically characterized. The compound [Me₂NH₂]₆[(Ge₂Sb₂S₇)(Ge₄S₁₀)] ( 1 ) features two distinct tetranuclear [Ge₂Sb₂S₇]^2? and [Ge₄S₁₀]^4? isolated clusters. The compound [(Me)₂NH₂][DabcoH]₂[Ge₂Sb₃S₁₀] ( 2 ) (Dabco=triethylenediamine) features a 1D‐[Ge₂Sb₃S₁₀]_n^3n? ribbon constructed with two [GeSbS₅]_n^3n? chains bridged by Sb³⁺ ion in ψ‐SbS₄ configuration. Compounds [M(en)₃][GeSb₂S₆] (M=Ni ( 3 ), Co ( 4 ) en=ethylenediamine) feature the unique 2D grid layer structures of [GeSb₂S₆]_n^2n?. The compound [(Me)₂NH₂]₂[GeSb₂S₆] ( 5 ) previously reported by us features a 3D chiral microporous structure with the chiral channels. The optical absorption spectra indicate that all the compounds are wide bandgap semiconductors. Thermal stabilities of these compounds have been investigated by thermogravimetric analyses (TGA).     

Encasing of Na+ ion in dimer‐formed acetic acid clusters

Peaks with anomalous abundance found in the mass spectra are associated with ions with enhanced stability. Among the scientific community focused on mass spectrometry, these peaks are called ‘magic peaks’ and their stability is often because of suggestive symmetric structures. Here, we report findings on ionised Na‐acetic acid clusters [Na⁺‐(AcA)_n] produced by Na‐doping of (AcA)_n and UV laser ionisation. Peaks labelled n = 2, 4, 8 are clearly distinguishable in the mass spectra from their anomalous intensity. Ab initio calculations helped elucidate cluster structures and energetic. A plausible interpretation of the magic peaks is given in terms of (AcA)_n formed by dimer aggregation. The encasing of Na⁺ by twisted dimers is proposed to be the origin of the enhanced cluster stability. A conceivable dimer‐formed tube‐like closed structure is found for the Na⁺‐(AcA)₈. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthese und Struktur eines Pentaalkylchlorohexastibans Sb6R5Cl [R = (Me3Si)2CH]

Synthesis and Structure of Pentaalkylchlorohexastibane Sb₆R₅Cl [R = (Me₃Si)₂CH] The reaction of RSbCl₂ [R = (Me₃Si)₂CH] with Na‐K alloy in tetrahydrofuran gives besides the known rings Sb_nR_n (n = 3, 4), (Me₃Si)₂CH₂ and the pentaalkylchlorohexastibane Sb₆R₅Cl ( 1 ). 1 was characterized by spectroscopic methods (MS, ¹H‐, ¹³C‐NMR, X‐ray diffraction). The structure of 1 consists of a folded four membered antimony ring in the all‐trans configuration with three alkyl groups and one Sb(R)—Sb(R)Cl fragment as substituents.     

Synthesis,Structures, Luminescent and Magnetic Properties of Heterometallic 5p‐4f Compounds with Ethylenediaminetetra­acetate

A series of heterometallic Ln^III–Sb^III edta‐containing compounds with the formulas [Sb₂(edta)₂Ln]NO₃ · nH₂O [edta = ethylenediaminetetraacetate; Ln = Eu, n = 7 ( 1 ); Gd, n = 7.5 ( 2 ) and Tb, n = 8 ( 3 )] were synthesized and characterized by elemental analyses (EA), powder X‐ray diffraction (PXDP), Fourier transform infrared spectroscopy (FT‐IR), and thermogravimetric analyses (TGA). Their fluorescence and magnetic properties were also studied. The thermal analysis demonstrates the compounds formation of the antimony, lanthanide ions, and edta^4– ligands. FT‐IR spectra reveal that the antimony and lanthanide ions are connected through the carboxylate bridges. The studies of luminescence properties show that compounds 1 and 3 exhibit typical luminescence in the visible region. Furthermore, magnetic properties reveal compounds 2 and 3 have weak ferromagnetic behavior.     

Combination of Metal Coordination Tetrahedra and Asymmetric Coordination Geometries of Sb(III) in the Organically Directed Chalcogenidometalates: Structural Diversity and Ion‐exchange Properties

Chalcogenidometalates exhibit rich and diverse structures and properties applicable to ion exchange, thermoelectrics, photocatalysis, nonlinear optics, and so on. This personal account summarizes our recent progress in constructing chalcogenidometalates by combining metal coordination tetrahedra and the asymmetric coordination geometries of Sb³⁺ in the presence of organic species (typically organic amines and metal‐organic amine complexes), which has been demonstrated as an effective strategy for synthesizing chalcogenidometalates with diversified structures and interesting properties. The linkage modes of asymmetric SbQ_n (n = 3, 4) geometries and group 13 (or 14) metal coordination tetrahedra are analyzed, and the secondary building units (SBUs), with different compositions and architectures, are clarified. The crucial role and function of organic species in the formation of chalcogenidometalates are explored, with an emphasis on their powerful structure‐directing features. In particular, some chalcogenidometalates in this family exhibit excellent ion‐exchange properties for Cs⁺ and/or Sr²⁺ ions; the factors affecting ion‐exchange properties are discussed to understand the underlying ion‐exchange mechanism.     

High‐Nuclearity Silver Thiolate Clusters Constructed with Phosphonates

The n‐butylphosphonate ligand has been employed to construct three new silver(I) thiolate compounds. Single‐crystal X‐ray analysis revealed that complexes 1 and 2 are Ag₄₈ and Ag₅₁ coordination chain polymers, while 3 contains a discrete Ag₄₈ cluster, in which three different kinds of silver(I) thiolate cluster shells enclose three different phosphonate‐functionalized silver(I) cluster cores, respectively. The structures of clusters in 1 – 3 feature three three‐shell arrangements, S@Ag₁₂@(nBuPO₃)₉@Ag₃₆S₂₃, S@Ag₁₁@(nBuPO₃)₇(MoO₄)₂ @Ag₄₀S₂₇ and MoO₄@Ag₁₂@(nBuPO₃)₈S₆ @Ag₃₆S₂₄, respectively.     

Theoretical study of silicon–sulfur clusters (SiS2)n− (n=1–6)

The possible geometrical structures and relative stability of silicon–sulfur clusters (SiS₂) (n=1–6) are explored by means of density functional theory (DFT) quantum chemical calculations. We also compare DFT with second‐order Møller–Plesset (MP2) and Hartree–Fock (HF) methods. The effects of polarization functions, diffuse functions, and electron correlation are included in MP2 and B3LYP quantum chemical calculations, and B3LYP is effective in larger cluster structure optimization, so we can conclude that the DFT approach is useful in establishing trends. The electronic structures and vibrational spectra of the most stable geometrical structures of (SiS₂)_n⁻ are analyzed by B3LYP. As a result, the regularity of the (SiS₂)_n⁻ cluster growing is obtained, and the calculation may predict the formation mechanism of the (SiS₂)_n⁻ cluster. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 280–290, 2001     

Far‐Infrared Spectra of Yttrium‐Doped Gold Clusters AunY (n=1–9)

The geometric, spectroscopic, and electronic properties of neutral yttrium‐doped gold clusters Au_nY (n=1–9) are studied by far‐infrared multiple photon dissociation (FIR‐MPD) spectroscopy and quantum chemical calculations. Comparison of the observed and calculated vibrational spectra allows the structures of the isomers present in the molecular beam to be determined. Most of the isomers for which the IR spectra agree best with experiment are calculated to be the energetically most stable ones. Attachment of xenon to the Au_nY cluster can cause changes in the IR spectra, which involve band shifts and band splittings. In some cases symmetry changes, as a result of the attachment of xenon atoms, were also observed. All the Au_nY clusters considered prefer a low spin state. In contrast to pure gold clusters, which exhibit exclusively planar lowest‐energy structures for small sizes, several of the studied species are three‐dimensional. This is particularly the case for Au₄Y and Au₉Y, while for some other sizes (n=5, 8) the 3D structures have an energy similar to that of their 2D counterparts. Several of the lowest‐energy structures are quasi‐2D, that is, slightly distorted from planar shapes. For all the studied species the Y atom prefers high coordination, which is different from other metal dopants in gold clusters.     

Structural connectivity and formation mechanism of monometallic cluster fullerenes YCN@Cn (n = 68–84)

Excited by the recently experimental reports of monometallic cluster fullerenes, we examined the electronic and geometrical properties of monometallic cluster fullerenes YCN@C_n with size from C₆₈ to C₈₄ by density functional theory and statistical thermodynamic calculations. The calculations demonstrate that the thermodynamically favored isomers of YCN@C_n are in good agreement with available experimental results. Morphology analysis shows that the lowest‐energy YCN@C_n species are structurally connected by C₂ insertion/extrusion and Stone–Wales rotation, which can be promoted under high temperature; enthalpy–entropy interplay can change the relative abundances of low‐energy isomers significantly at high temperature. All the results suggest that there is a structural evolution among these metallic cluster fullerenes in discharge condition, and thus, can rationalize their structural diversity in the soot and partly disclose their formation mechanism. The geometrical structures, electronic properties of these endohedral fullerene were discussed in detail.     

Li2 Trapped inside Tubiform [n] Boron Nitride Clusters (n=4–8): Structures and First Hyperpolarizability

The geometries and electronic properties of tubiform [n] boron nitride clusters entrapping Li₂ (Li₂@BN‐cluster(n,0); n=4–8), obtained by doping BN‐cluster(n,0) with Li₂ molecules, are investigated by means of DFT. The effects of tube diameter n on the dipole moment μ₀, static polarizability α₀, and first hyperpolarizability β₀ are elucidated. Both the dipole moment and polarizability increase with increasing tube diameter, whereas variation of the static first hyperpolarizability with tube diameter is not monotonic; β₀ follows the order 1612 (n=4)<3112 (n=5)<5534 (n=7)<8244 (n=6)<12 282 a.u. (n=8). In addition, the natural bond orbital (NBO) charges show that charge transfer takes place from the Li₂ molecule to the BN cluster, except for BN‐cluster(8,0) with larger tube diameter. Since the large‐diameter tubular BN‐cluster(8,0) can trap the excess electrons of the Li₂ molecule, Li₂@BN‐cluster(8,0) can be considered to be a novel electride compound.     

Ternary Transition Metal Antimonides T5T' 1‐xSb2+x (T = Ti,Zr, Hf; T' = Fe,Co, Ni,Cu, Ru,Rh, Pd,Cd) with Nb5SiSn2 (Ordered W5Si3, Filled V4SiSb2) Type Structure

Fifteen new ternary antimonides T₅T' _1‐xSb_2+x were synthesized by reaction of the elemental components in an arc‐melting furnace. They crystallize with a tetragonal structure first reported for Nb₅SiSn₂ (space group I4/mcm, Z = 4.) A structure refinement from four‐circle X‐ray diffractometer data of Hf₅Fe_1‐xSb_2+x (a = 1086.0(1) pm, c = 550.1(1) pm, R = 0.033 for 270 structure factors and 18 variable parameters) showed deviations from the ideal occupancy for two atomic sites, resulting in the composition Hf_4.929(3)Fe_0.67(1)Sb_2.33(1). Structure refinements from X‐ray powder data resulted in the formula Ti₅Ni_0.45(2)Sb_2.55(2), while no deviation from the ideal composition was observed for Ti₅RhSb₂. The crystal structures of these compounds are discussed together with those of related binary and ternary compounds.     

Solvothermal Synthesis of two 2‐D Thioantimonates(III) with Metal Complexes as Template Ions, [M(dap)3]Sb4S7 (M = Ni2+ and Co2+)

Two new thioantimonates [M(dap)₃]Sb₄S₇ (M = Ni²⁺ ( 1 ) and Co²⁺ ( 2 )) were synthesized under solvothermal conditions by the reaction of NiS (or Co metal), Sb and S in an aqueous solution of 1,2‐diaminopropane (dap). Compounds 1 and 2 are isostructural. The polymeric [Sb₄S₇^2?]_n anion is composed of two SbS₃ trigonal pyramids and two SbS₄ units. The SbS₃ and SbS₄ units are interconnected by corners and edges to build a 2‐D puckered layer with Sb₄S₄ and Sb₁₆S₁₆ heterorings. The apertures of the large Sb₁₆S₁₆ hetero‐rings are filled by two [M(dap)₃]²⁺ complex cations which serve as template ions. The band gaps of 2.44 eV for 1 and 2.43 eV for 2 have been estimated from optical absorption spectra.