Synthesis and structural characterization of an AI77 cluster

Ecker, Achim; Weckert, E.; Schnöckel, Hansgeorg

doi:10.1038/387379a0

Cited by 259 publications

(217 citation statements)

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“…To answer such questions is crucial when one attempts to find other examples. In the present note we report a 27 Al NMR study on Al 50 Cp* 12 , which is another giant molecular cluster compound recently discovered [22], where Cp* = pentamethylcyclopentadienyl = C 5 (CH 3 ) 5 . Writing the chemical formula as Al 50 C 120 H 180 underlines the fact that the molecular structure can be briefly described as a pseudofullerene shell of 60 carbon atoms and 60 methyl groups, protecting a cluster core of 50 Al atoms.…”

Section: Introductionmentioning

confidence: 99%

“…The synthesis of molecular metal cluster compounds presents an attractive chemical route for the generation of self-organized nanostructures composed of 3D ordered arrays of identical metal nanoparticles embedded in a dielectric matrix [1][2][3][4][5][6][7][8][9]. These stoichiometric compounds form macromolec-ular solids, in which the cores of the macromolecules can be seen as minute pieces (clusters) of metals, surrounded by shells of ligand molecules, which pacify the bonds left open at the surfaces of the metal cores in order to prevent the thermodynamically favored formation of the bulk metal.…”

Section: Introductionmentioning

confidence: 99%

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27Al NMR Study of the Metal Cluster Compound Al50C120H180

et al. 2007

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We present an 27 Al NMR study of the metal cluster compound Al 50 Cp* 12 which is composed of (identical) Al 50 clusters, each surrounded by a Cp* ligand shell, and arranged in a crystalline 3D array (here Cp* = pentamethylcyclopentadienyl = C 5 (CH 3 ) 5 ). The compound is found to be non-conducting, the nuclear spin-lattice relaxation in the temperature range 100-300 K being predominantly due to reorientational motions of the Cp* rings. These lead to a pronounced maximum in the relaxation rate at T $ 170 K, corresponding to an activation energy of about 850 K. Data for the related compound Al 4 Cp* 4 , containing very much smaller Al 4 clusters are also presented. A comparison is drawn with the quadrupolar relaxation recently observed for the non-conducting fraction of Ga 84 molecules in the metal cluster compound Ga 84 [N(SiMe 3 ) 2 ] 20 -Li 6 Br 2 (thf) 20 AE2toluene.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

27Al NMR Study of the Metal Cluster Compound Al50C120H180

et al. 2007

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“…19 For the case of aluminum, the only systems that have been observed to crystallize contain either Cp and Cp * ligands bound in a roughly η 5 cona) Electronic mail: jphooper@nps.edu figuration, or N(SiMe 3 ) 2 with the surface aluminum bound directly to nitrogen. 12 Other ligand-stabilized metal clusters are known in addition to the aluminum compounds; thiolprotected gold clusters, for example, have received significant recent attention due to their application in nanomedicine and biochemistry. 8,9,20 Beyond the basic interest in ligand-protected cluster stability, there is also recent interest in the use of small aluminum clusters as catalysts for producing hydrogen from water 21,22 or as high energy-density fuels.…”

Section: Introductionmentioning

confidence: 99%

“…These systems, first synthesized by Schnöckel and co-workers, [10][11][12][13][14][15][16] form in a gas-phase disproportionation reaction starting from monovalent aluminum precursor compounds. The structure of the metallic core is generally dissimilar from that of the gas-phase pure metal cluster or bulk aluminum, though recent work has suggested that a modified superatom model might be used to treat its electronic structure.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

Alnemrat

Hooper

2014

The Journal of Chemical Physics

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Oxidation of ligand-protected aluminum clusters: an ab-initio molecular dynamics study. "J. Chem. Phys. 140, 104313 (2014 We report Car-Parrinello molecular dynamics simulations of the oxidation of ligand-protected aluminum clusters that form a prototypical cluster-assembled material. These clusters contain a small aluminum core surrounded by a monolayer of organic ligand. The aromatic cyclopentadienyl ligands form a strong bond with surface Al atoms, giving rise to an organometallic cluster that crystallizes into a low-symmetry solid and is briefly stable in air before oxidizing. Our calculations of isolated aluminum/cyclopentadienyl clusters reacting with oxygen show minimal reaction between the ligand and O 2 molecules at simulation temperatures of 500 and 1000 K. In all cases, the reaction pathway involves O 2 diffusing through the ligand barrier, splitting into atomic oxygen upon contact with the aluminum, and forming an oxide cluster with aluminum/ligand bonds still largely intact. Loss of individual aluminum-ligand units, as expected from unimolecular decomposition calculations, is not observed except following significant oxidation. These calculations highlight the role of the ligand in providing a steric barrier against oxidizers and in maintaining the large aluminum surface area of the solid-state cluster material. [http://dx

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“…[13][14][15][16][17] Aluminum(I) halide solutions have been used as precursors to form a variety of organoaluminum complexes such as Al 4 Recent theoretical analysis has suggested that these may also be analyzed with a modified jellium model, and that the observed organoaluminum clusters such as Al 4 Cp * 4 may represent stable magic-number forms. 18,19 This may result in hindered reactions with O 2 due both to electronic structure effects as well as the physical steric barrier of the ligands surrounding the metal core.…”

Section: Introductionmentioning

confidence: 99%

Ab initio metadynamics simulations of oxygen/ligand interactions in organoaluminum clusters

Alnemrat

Hooper

2014

The Journal of Chemical Physics

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. Prior to reaction with the aluminum core, simulations suggest that the oxygen undergoes a hindered crossing of the steric barrier presented by the outer ligand monolayer. A combination of two collective variables based on aluminum/oxygen distance and lateral oxygen displacement was found to produce distinct reactant, product, and transition states for this process. In the methylated cluster with Cp * ligands, a broad transition state of 45 kJ/mol was observed due to direct steric interactions with the ligand groups and considerable oxygen reorientation. In the non-methylated cluster the ligands distort away from the oxidizer, resulting in a barrier of roughly 34 kJ/mol with minimal O 2 reorientation. A study of the oxygen/cluster system fixed in a triplet multiplicity suggests that the spin state does not affect the initial steric interaction with the ligands.The metadynamics approach appears to be a promising means of analyzing the initial steps of such oxidation reactions for ligand-protected clusters. [http://dx

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Synthesis and structural characterization of an AI77 cluster

Cited by 259 publications

References 10 publications

27Al NMR Study of the Metal Cluster Compound Al50C120H180

27Al NMR Study of the Metal Cluster Compound Al50C120H180

Oxidation of ligand-protected aluminum clusters: An ab initio molecular dynamics study

Ab initio metadynamics simulations of oxygen/ligand interactions in organoaluminum clusters

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