Double Aromaticity in “Boron Toroids”

Bean, David E.; Fowler, Patrick W.

doi:10.1021/jp905926j

Cited by 40 publications

(43 citation statements)

References 29 publications

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“…Figure 2(b) reveals that there are fourteen 3c-2e BBB bonds, three 14c-2e delocalized bonds, and nine delocalized 15c-2e bonds. The bonding model of these 3c-2e bonds are in accordance with the BBB bonds in all boron clusters B 14 and B 14 2+ , 70,79 which indicates that these 3c-2e bonds do not interact with the central Ni. Compared with the CMO results, it is clearly shown that the three 14c-2e bonds are delocalized π orbitals in the tangential direction, which almost have no contribution for the Ni-B 14 endohedral bonding.…”

Section: B Electronic Structuressupporting

confidence: 59%

“…A recent study 79 reveals that the double-ring B 2n (n = 6-14) clusters have two directional delocalized orbitals. For even n, there are 4m + 2 electrons in both radial and tangential delocalized orbitals following the Huckle's rule, respectively, implying the double aromaticity; for odd n, there are 4m + 2 electrons in tangential or radial orbitals alternatively and the rest orbitals are occupied with 4m electrons, which indicate the complexes are in conflicting aromaticity.…”

Section: B Electronic Structuresmentioning

confidence: 99%

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Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

Cheng

Yang

2014

The Journal of Chemical Physics

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It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

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Section: B Electronic Structuressupporting

confidence: 59%

Section: B Electronic Structuresmentioning

confidence: 99%

Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

Cheng

Yang

2014

The Journal of Chemical Physics

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“…At small cluster size, all of the theoretical and experimental studies suggested that (quasi-)planar isomers are most stable. [8][9][10][11][12][13][14][15][16][17] A structural transformation from (quasi-)planar to double-ring tubular structures occurs in the size range of B 16 to B 24 , depending on the charge state of the clusters. 13,[18][19][20][21][22] For larger boron clusters, some tubular, cage, and core-shell structures are theoretically suggested.…”

Section: Introductionmentioning

confidence: 99%

B14: An all-boron fullerene

Cheng

2012

The Journal of Chemical Physics

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Experiments revealed that small boron cluster anions and cations are (quasi-)planar. For neutral boron cluster, (quasi-)planar motifs are also suggested to be global minimum by many theoretical studies, and a structural transformation from quasi-planar to double-ring tubular structures occurs at B(20). However, a missing opportunity is found for neutral B(14), which is a flat cage and more stable than the previous quasi-planar one by high level ab initio calculations. The B(14) cage has a large HOMO-LUMO gap (2.69 eV), and NICS values reveal that it is even more aromatic than the known most aromatic quasi-planar B(12) and double-ring B(20), which indicates a close-shell electronic structure. Chemical bonding analysis given by AdNDP reveals that the B(14) cage is an all-boron fullerene with 18 delocalized σ-electrons following the 2(n+1)(2) rule of spherical aromaticity. The geometry and bonding features of the B(14) cage are unique denying conversional thinking.

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“…On the other hand, hysteresis loop of a rock sample as a whole can have unusual shapes including a wasp-waisted shape that is constricted in the middle [15][16][17]. The wasp-waisted shape is thought to arise from the fact that the grains dispersed in the rock have a distribution of sizes, domain states, and coercive fields [15][16][17][18][19][20][21][22][23][24][25][26][27]. One would like to determine the distribution of magnetic grains from the hysteresis loop of the rock sample.…”

Section: Introductionmentioning

confidence: 99%