Disk Aromaticity of the Planar and Fluxional Anionic Boron Clusters B<sub>20</sub><sup>−/2−</sup>

Tai, Truong Ba; Ceulemans, Arnout; Nguyen, Minh Tho

doi:10.1002/chem.201104064

Cited by 98 publications

(84 citation statements)

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“…[3] At this turning point, the boron clusters B 19 À and B 20 À still prefer planar geometries and have fluxional behaviour. [4][5] The delocalisation of the electrons in B 20 À led Tai et al [5] to propose a new type of disk aromaticity for planar boron clusters. In contrast to these negatively charged structures, neutral B 20 adopts a double-ring structure and is therefore considered as a precursor for boron single-walled nanotubes.…”

Section: Introductionmentioning

confidence: 99%

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

et al. 2013

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Extensive optimisation calculations are performed for the B(80) isomers in order to find out which principles underlie the formation of large hollow boron cages. Our analysis shows that the most stable isomers contain triangular B(10) or rhombohedral B(16) building blocks. The lowest-energy isomer has C(3v) symmetry and is characterised by a belt of three interconnected B(16) units and two separate B(10) units. At the B3LYP/6-31G(d) level of theory, this newly discovered isomer is 2.29, 1.48, and 0.54 eV below the leapfrog B(80) of Szwacki et al., the T(h) -B(80) of Wang, and the D(3d) -B(80) of Pochet et al., respectively. Our C(3v) isomer is therefore identified as the most stable hollow cage isomer of B(80) presently known. Its HOMO-LUMO gap of 1.6 eV approaches that of the leapfrog B(80). The leapfrog principle still remains a reliable scheme for producing boron cages with larger HOMO-LUMO gaps, whereas the thermodynamically most stable B(80) cages are formed when all pentagonal faces are capped. We show that large hollow cages of boron retain a preference for fullerene frames. The additional capping is in accordance with the following rules: preference for capping of pentagonal faces, formation of B(10) and/or B(16) units, homogeneous distribution of the hexagonal caps, and hole density approaching 1/9. Although our most stable B(80) isomer still remains higher in energy than the B(80) core-shell structure, we show that by applying the bonding principles to larger structures it is possible to construct boron cages with higher stabilisation energy per boron atom than the core-shell structure; a prototypical example is B(160). This clearly shows the continuous competition between the two suggested construction schemes, namely, the formation of multiple-shell structures and hollow cages.

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Section: Introductionmentioning

confidence: 99%

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

et al. 2013

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“…Boron-based nanoclusters are af ertile ground for unique quasi-planar (2D) structures up to 40 atoms, [1][2][3][4][5][6] extreme coordination environments, [1] and intriguing dynamic properties; [7][8][9][10][11][12][13][14][15][16][17] all these phenomena are attributed to the electron deficiencyo fb oron. During the past decades,n anomachines (including molecular rotors) [18] have emerged as ahot topic in chemistry and nanoscience.Aspectroscopic study of Zhai, Wang, and Boldyrev in 2010 on a2Dwheel-like B 19 À cluster [4] sparked an immediate proposal of molecular Wankel motor by Merino,Heine,and co-workers, [7] which was subsequently extended to aseries of circular clusters:B 13 + ,B 18 2À ,B 20 2À ,and B 12 Ir À .…”

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confidence: 99%

“…During the past decades,n anomachines (including molecular rotors) [18] have emerged as ahot topic in chemistry and nanoscience.Aspectroscopic study of Zhai, Wang, and Boldyrev in 2010 on a2Dwheel-like B 19 À cluster [4] sparked an immediate proposal of molecular Wankel motor by Merino,Heine,and co-workers, [7] which was subsequently extended to aseries of circular clusters:B 13 + ,B 18 2À ,B 20 2À ,and B 12 Ir À . [8][9][10][11][12][13][14] Elongated boron clusters (B 11 ,B 11 À ,a nd B 15 + )…”

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Coaxial Triple‐Layered versus Helical Be₆B₁₁⁻ Clusters: Dual Structural Fluxionality and Multifold Aromaticity

et al. 2017

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Tw olow-lying structures are unveiled for the Be 6 B 11 À nanocluster system that are virtually isoenergetic.T he first, triple-layered cluster has aperipheral B 11 ring as central layer, being sandwiched by two Be 3 rings in acoaxial fashion, albeit with no discernible interlayer BeÀBe bonding.T he B 11 ring revolves like aflexible chain even at room temperature,gliding freely around the Be 6 prism. At elevated temperatures (1000 K), the Be 6 core itself also rotates;t hat is,t wo Be 3 rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four-fold (p and s)a romaticity, offering adilute and fluxional electron cloud that lubricates the dynamics.The second, helix-type cluster contains aB 11 helical skeleton encompassing adistorted Be 6 prism. It is chiral and is the first nanosystem with ab oron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple-layered one.

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“…9 The bowl-shaped B 30 , B 32 and B 36 10,11,12 and quasi-planar B 35 13 clusters can serve as building blocks to form various boron sheets. 16,17,18 The boron atom has the capacity to form strong covalent bonds not only with itself but also with many other elements. Let us note that in both B 38 and B 40 sizes, the fullerenes 10,15 and the quasi-planar isomes 9 are quite close in energy content.…”

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Effects of bimetallic doping on small cyclic and tubular boron clusters: B₇M₂and B₁₄M₂structures with M = Fe, Co

Pham

Nguyen

2015

Phys. Chem. Chem. Phys.

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Using density functional theory with the TPSSh functional and the 6-311+G(d) basis set, we extensively searched for the global minima of two metallic atoms doped boron clusters B6M2, B7M2, B12M2 and B14M2 with transition metal element M being Co and Fe. Structural identifications reveal that B7Co2, B7Fe2 and B7CoFe clusters have global minima in a B-cyclic motif, in which a perfectly planar B7 is coordinated with two metallic atoms placed along the C7 axis. The B6 cluster is too small to form a cycle with the presence of two metals. Similarly, the B12 cluster is not large enough to stabilize the metallic dimer within a double ring 2 × B6 tube. The doped B14M2 clusters including B14Co2, B14Fe2 and B14CoFe have a double ring 2 × B7 tubular shape in which one metal atom is encapsulated by the B14 tube and the other is located at an exposed position. Dissociation energies demonstrate that while bimetallic cyclic cluster B7M2 prefers a fragmentation channel that generates the B7 global minimum plus metallic dimer, the tubular structure B14M2 tends to dissociate giving a bimetallic cyclic structure B7M2 and a B@B6 cluster. The enhanced stability of the bimetallic doped boron clusters considered can be understood from the stabilizing interactions between the anti-bonding MOs of metal-metal dimers and the levels of a disk aromatic configuration (for bimetallic cyclic structures), or the eigenstates of the B14 tubular form (in case of bimetallic tubular structure).

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Disk Aromaticity of the Planar and Fluxional Anionic Boron Clusters B₂₀^−/2−

Cited by 98 publications

References 20 publications

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

Coaxial Triple‐Layered versus Helical Be₆B₁₁⁻ Clusters: Dual Structural Fluxionality and Multifold Aromaticity

Effects of bimetallic doping on small cyclic and tubular boron clusters: B₇M₂and B₁₄M₂structures with M = Fe, Co

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Disk Aromaticity of the Planar and Fluxional Anionic Boron Clusters B20−/2−

Cited by 98 publications

References 20 publications

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

The Boron Conundrum: Which Principles Underlie the Formation of Large Hollow Boron Cages?

Coaxial Triple‐Layered versus Helical Be6B11− Clusters: Dual Structural Fluxionality and Multifold Aromaticity

Effects of bimetallic doping on small cyclic and tubular boron clusters: B7M2and B14M2structures with M = Fe, Co

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Product

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Disk Aromaticity of the Planar and Fluxional Anionic Boron Clusters B₂₀^−/2−

Coaxial Triple‐Layered versus Helical Be₆B₁₁⁻ Clusters: Dual Structural Fluxionality and Multifold Aromaticity

Effects of bimetallic doping on small cyclic and tubular boron clusters: B₇M₂and B₁₄M₂structures with M = Fe, Co