Icosahedral Metal Research Articles

Carbon-free sandwich compounds based on arsenic and antimony with icosahedral metal cores

Carbon-free sandwich compounds based on arsenic and antimony with icosahedral metal cores

Photo-induced image current

We study the possibility of generation of photo-induced image currents at a distance from the surface of nano-sized metal clusters by using the time-dependent perturbation theory. We reveal that the wave function of an electron excited to the image state is localized outside the surface and the current flows in a spherical shell whose radius is a few times the radius of the sphere. Circularly polarized light has been applied to a perfect icosahedral metal cluster Li13 whose optimization is achieved by molecular dynamic simulation and band structure is obtained by the DFT method and by the solution of the radial Schrödinger equation. To the best of our knowledge, despite the great effort put into determining their characteristics, image electrons have not been the subject of studies on photo-induced current.

Electrochemistry of icosahedral metal full and half sandwich metallacarboranes in phosphate buffers

• Electrochemistry of sandwich (Cr, Fe Co, Ni) metallacarbores in aqueous solution. • The electrochemical process connected with metal atom is reversible. • Electrochemical processes connected with the boron cage are irreversible. Electrochemical behavior of metallacarboranes containing different central coordination atoms – Co, Cr, Ni and Fe – in aqueous phosphate buffers is described in this study. Also, the effects of number of the dicarbaborane ligands present in the metallacarborane and the influence of mixed or polydecker sandwich structure on the electrochemical activity were studied. In general, we found two distinctive regions of electrochemical activity. One of them is located in the negative potential range and corresponds to redox process on the central metal atom. The second one is located in the positive potential region and is connected to core cage oxidation process. The results revealed clearly promising properties of majority of studied metallacarboranes to be used as electrochemical tags in aqueous solutions, with potentially better properties that the known and widely studied cobalt bis(dicarbollide)(1-) ion based systems.

Intermetallic Compounds NakMn (М = K, Cs, Ba, Ag, Pt, Au, Zn, Bi, Sb): Geometrical and Topological Analysis, Cluster Precursors, and Self-Assembly of Crystal Structures

A geometrical and topological analysis has been performed, and self-assembly of the crystal structures of intermetallic compounds formed in the Na–M (M = K, Cs, Ba, Ag, Pt, Au, Zn, Bi, Sb) systems has been simulated using computer methods (the ToposPro software). The NakMn precursor metal clusters of the crystal structures are determined based on the algorithms of structural-graph decomposition in cluster structures and construction of the basic net of the structure in the form of a graph whose nodes correspond to the cluster centers. The tetrahedral metal clusters M4, forming packets in the Na3Bi-hP8, Na2Bi2-tP4, and Na2Sb2-mP16 crystal structures; tetrahedral metal clusters M4 and spacers for the Na2(Au4)-cF24 and Ba2(Na4)-hP12 framework structures; octahedral clusters M6 for the Na4Au2-tI12 structure; octahedral M6 and tetrahedral M4 metal clusters for the Na2(Na4)(Ba6)-cF96 and Au2(In4)(Na6)-cF96 structures; and icosahedral metal clusters M13 for the Na(Zn13)-cF116 structure are found. The symmetry and topology code of the self-assembly of crystal structures of NakMn intermetallic compounds has been reconstructed from precursor metal clusters $$S_{3}^{0}$$ in the following form: primary chain $$S_{3}^{1}$$ → microlayer $$S_{3}^{2}$$ → microframework $$S_{3}^{3}$$ .

From Octahedral to Icosahedral Metal-Organic Polyhedra Assembled from Two Types of Polyoxovanadate Clusters.

Design and synthesis of metal-organic polyhedra (MOPs) with targeted geometries from predetermined secondary building units (SBUs) is a long-standing challenge in chemistry and material science. Theoretical prediction shows that there are 6 possible polyhedra from the 3-coordinated, 4-coordinated octahedron ((3,4)-c octahedron) to (3,5)-c icosahedron with minimal transitivity (simplest possible). Except for one missing polyhedron (mtr) due to the unfavorable angles, we report five MOPs based on these structures, including an octahedral (3,4)-c VMOP-21 (rdo), an icosahedral (3,5)-c VMOP-25 (trc), and three intermediate derived trinodal (3,4,5)-c VMOP-22-24 (ghm, hmg, xum). Remarkably, all these MOPs obey the minimal transitivity principle and are consistent with geometrical predictions.

From Octahedral to Icosahedral Metal–Organic Polyhedra Assembled from Two Types of Polyoxovanadate Clusters

AbstractDesign and synthesis of metal–organic polyhedra (MOPs) with targeted geometries from predetermined secondary building units (SBUs) is a long‐standing challenge in chemistry and material science. Theoretical prediction shows that there are 6 possible polyhedra from the 3‐coordinated, 4‐coordinated octahedron ((3,4)‐c octahedron) to (3,5)‐c icosahedron with minimal transitivity (simplest possible). Except for one missing polyhedron (mtr) due to the unfavorable angles, we report five MOPs based on these structures, including an octahedral (3,4)‐c VMOP‐21 (rdo), an icosahedral (3,5)‐c VMOP‐25 (trc), and three intermediate derived trinodal (3,4,5)‐c VMOP‐22–24 (ghm, hmg, xum). Remarkably, all these MOPs obey the minimal transitivity principle and are consistent with geometrical predictions.

Hollow Versus Hydrogen-Occupied Icosahedral Cages of Coinage–Metal Clusters

It is suggested that the hollow coinage–metal icosahedral cage of the [Ag44(SR)30]4− tetraanion (1a) may be occupied by two hydrogen atoms, giving rise to a dihydridic cluster [H2Ag44(SR)30]4− tetraanion (2b). As a consequence, two series of clusters, with different electron counts, can be formed by chemical means: the 18-electron series [H x Ag44(SR)30](4−x)− via stepwise protonation of 1a and the 20-electron series [H x Ag44(SR)30](6−x)− via stepwise deprotonation of 2b (here x = 0, 1, 2). Both series are closed-shell Jelliumatic clusters and expected to be stable. The corresponding members of these two series (for a given x value) are related by a two-electron reduction. These pairs raise the possibility of the hollow icosahedral metal cages in housing a number of hydrogen atoms, either via stepwise protonations or by absorption of hydrogen molecules.

On the icosahedral metal–phosphorus coordination in melliniite: a gift from the sky for materials chemistry

Recently a new mineral, melliniite, was reported from a meteorite sample. This mineral has an ideal chemical composition of (Ni,Fe)4P and a crystal structure where the phosphorus atoms are coordinated by twelve nearest neighboring metal atoms. No other phosphide has been reported to have such high metal coordination. Therefore melliniite provides new and important information about the chemical interaction in transition metal chalcogenides and possibly pnictides. We demonstrate here, using first principles theory, that the stability and icosahedral metal–phosphorous coordination of melliniite are due to a balance between covalent Fe–P binding, configurational entropy and a weaker nickel–phosphorus binding, that has only a weak directional dependence.

Metal Complexes of Monocarbon Carboranes Bearing C‐Amine or ‐Amino Substituents

AbstractFor Abstract see ChemInform Abstract in Full Text.

Amorphization mechanism of icosahedral metal nanoclusters.

The amorphization mechanism of icosahedral Pt nanoclusters is investigated by a combination of molecular dynamics simulations and density functional calculations. A general mechanism for amorphization, involving rosettelike structural transformations at fivefold vertices, is proposed. In the rosette, a fivefold vertex is transformed into a hexagonal ring. We show that, for icosahedral Pt nanoclusters, this transformation is associated with an energy gain, so that their most favorable structures have a low symmetry even at icosahedral magic numbers, and that the same mechanism underlies the formation of amorphous structures in gold.

Application of the Duality Principle to Chiral Icosahedral Metal Complexes

Durch Anwendung des Dualitätsprinzips findet sich die für ikosaedrische Barium-, Strontium- oder Lanthan-Komplexe vor kurzem beschriebene Art der Chiralität auch für ein Tetrafluordodecahedran mit der gleichen T-Symmetrie (siehe Schema).

Modular design of icosahedral metal clusters

The concept of crystalline “module,” that is, an unambiguously isolated, repeated quasi-molecular element, is introduced. This concept is more general than the concept of crystal lattice. The generalized modular approach allows extension of the methods and principles of crystallography to quasi-crystals, clusters, amorphous solids, and periodic biological structures. Principles of construction of aperiodic, nonequilibrium regular modular structures are formulated. Limitations on the size of icosahedral clusters are due to the presence of spherical shells with non-Euclidean tetrahedral tiling in their structure. A parametric relationship between the structures of icosahedral fullerenes and metal clusters of the Chini series was found.

Molecular and crystal structure of an iodo-gold-silver-platinum cluster, [(Ph 3P) 6Au 6Ag 6Pt(AgI 3) 2](THF) 2, with a trimetallic icosahedral core capped with two planar [AgI 3] units

The synthesis and crystal structure of the first trimetallic iodo-gold-silver-platinum cluster, [(Ph 3P) 6Au 6Ag 6Pt(AgI 3) 2](THF) 2, with a centered icosahedral metal core and two planar AgI 3 capping units are described. The cluster core serves as the basic building block for a new series of trimetallic (AuAgPt) polyicosahedral clusters with iodo ligands. In the crystal, the clusters form a clathrate structural network capable of stabilizing weakly hydrogen-bonded (THF) 2 dimers.

Melting behaviors of icosahedral metal clusters studied by Monte Carlo simulations

We present an atom-resolved analysis method that traces physical quantities such as the root-mean-square bond length fluctuation and coordination number for individual atoms as functions of temperature or time. This method is applied to explain the temperature-dependent behaviors of three types of NiN (N=12,13,14) clusters. The detailed studies for the three types of clusters reveal characteristics as follows: (a) as the temperature increases, all three types of clusters undergo two-stage melting, irrespective of the existence of vacancy or adatom on the icosahedral surfaces, (b) the melting of icosahedral clusters with vacancy starts with vacancy hopping, which has not been observed for any type of small clusters (N<34), (c) the melting of the icosahedral clusters with adatom (N=14) is initiated by adatom hopping, followed by the site exchange between the adatom and surface atoms. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 380–387, 2000

Monoorganotin–polyoxometal compounds: Part 1. Synthesis and crystal structure of [( iPrSn) 11(V IVO)O 14(OH) 6]Cl·2DMF·H 2O. The first example in a series of monoorganotin–polyoxometal compounds with icosahedral metal arrangement and various contents of tin and vanadium

The synthesis, molecular and crystal structure of the [( i PrSn) 11(VO)O 14(OH) 6] + ion 1 are described. 1 was found in the compound 1·Cl·2DMF·H 2O and is the first oxovanadium derivative of the long-known [( i PrSn) 12O 14(OH) 6] 2+ ion 2. The green compound crystallizes in the triclinic space group P 1 ̄ with a=13.989(2), b=14.541(2), c=19.713(3) Å, α=97.16(1)°, β=93.79(1)°, γ=116.08(1)°, V=3540.5(9) Å 3, Z=2. 1 shows the same icosahedral arrangement of metal atoms as the tin compound as well as the same arrangement of oxygen atoms. The vanadium atom is coordinated by five oxygen atoms and replaces one of the square-pyramidally coordinated organotin groups. In the solid state the big cations are linked by hydrogen bonds to Cl − ions forming chains along the a axis. Two of these chains are linked by OH⋯OV hydrogen bonds resulting in a band structure.

Melting behaviors of icosahedral metal clusters studied by Monte Carlo simulations

We present an atom-resolved analysis method that traces physical quantities such as the root-mean-square bond length fluctuation and coordination number for individual atoms as functions of temperature or time. This method is applied to explain the temperature-dependent behaviors of three types of NiN (ND 12, 13, 14) clusters. The detailed studies for the three types of clusters reveal characteristics as follows: (a) as the temperature increases, all three types of clusters undergo two-stage melting, irrespective of the existence of vacancy or adatom on the icosahedral surfaces, (b) the melting of icosahedral clusters with vacancy starts with vacancy hopping, which has not been observed for any type of small clusters (N < 34), (c) the melting of the icosahedral clusters with adatom (ND 14) is initiated by adatom hopping, followed by the site exchange between the adatom and surface atoms. c 2000 John Wiley & Sons, Inc. J Comput Chem 21: 380-387, 2000

Icosahedral symmetry in clusters

First principles calculations and simulations based on interatomic potentials together with experimental studies of abundance spectrum suggest icosahedral structures to be common for some magic clusters of diverse systems such as rare gases, metals, covalently bonded systems and water. Close packing models obtained from pair potentials are shown to be good representations of the structure of rare gas clusters. However, the electronic structure is found to play the important role in the atomic structure and related properties of other clusters. Results of recent studies of fullerenes, their derivatives as well as some large icosahedral metal clusters containing several thousand atoms are also presented. Further results on doped icosahedral clusters are discussed which hold promise for the development of new materials and for understanding the occurrence of icosahedral order in several aluminum alloys.

Preparation, characterisation and properties of groups VIII and IB metal manoparticles

Vapour synthesis techniques have been used to prepare nanoparticulate dispersions of ruthenium, rhodium, palladium, platinum, silver and gold in non-aqueous solvents. The dimensions of these solvent-stabilised particles, which can be controlled within the 1–3 nm size regime, effectively encompass the areas of molecular chemistry (as typified by high-nuclearity metal clusters) and the smaller colloidal metals. The nanostructures have been characterised by high-resolution transmission electron microscopy and evidence for face-centred cubic (f.c.c.) octahedral, f.c.c. cuboctahedral and icosahedral metal particles obtained; quasi-molten states have also been observed in a number of these systems. In addition to discrete particles, larger aggregates of the small primary particles have been observed, some of which appear to be organometallic in nature. Gold nanoparticles differ from those of the Group VIII metals in exhibiting unusual time and concentration-dependent behaviour. A regime of preparative conditions under which 1–3 nm size gold particles, which are stable with respect to aggregation as a function of time, is defined. Some preliminary results of attempts to use laser mass spectrometry as a rapid method for the molecular mass determination of some of these materials are also described.

Synthesis and characterization of the centred icosahedral cluster series [Au9MIB 4Cl4(PMePh2)8][C2B9H12], where MIB= Au, Ag or Cu

The compounds [Au9MIB4Cl4(PMePh2)8][C2B9H12](MIB= Au, Ag or Cu) have been prepared from solutions of [Au11(PMePh2)10][C2B9H12]3 by the addition or formation in situ of [MIBCl(PMePh2)]. The reaction is believed to take place via the intermediate cations [Au11MIB2Cl2(PMePh2)10]3+ and [Au10MIB3Cl3(PMePh2)9]2+. The final products have been characterized by FAB mass spectrometry, electronic spectroscopy and 31P-{1H}, 11B-{1H} and 1H NMR spectroscopy. Single-crystal X-ray diffraction studies on [Au9Ag4Cl4(PMePh2)8][C2B9H12]·H2O·0.5CH2Cl2 and [Au9Cu4Cl4(PMePh2)8][C2B9H12]·CH2Cl2 have been carried out. The cations of these compounds contain centred icosahedral metal frameworks and in both cases the cages have approximate C2v symmetry: the silver and copper atoms, associated with the halide ligands, occupy identical positions. A gold atom sits at the interstitial site. The cations cannot be superimposed due to differences in the ligand packing. Comparable Au–Au bond lengths in the two structures are very similar and, given the large differences that are seen between the Au–Ag and the Au–Cu bond lengths, the Ag–Cl and Cu–Cl moieties can be visualized as moving relative to one another along radial vectors.