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Issue 42, 2016
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Competition between quasi-planar and cage-like structures in the B29 cluster: photoelectron spectroscopy and ab initio calculations

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Abstract

Size-selected boron clusters have been found to be predominantly planar or quasi-planar (2D) in the small size regime with the appearance of three-dimensional (3D) borospherene cages of larger sizes. A seashell-like B28 cluster was previously shown to be the smallest borospherene, which competes with a quasi-planar isomer for the global minimum. Here we report a study on the structures and bonding of the B29 and B29 clusters using photoelectron spectroscopy (PES) and first-principles calculations and demonstrate the continued competition between the 2D and borospherene structures. The PES spectrum of B29 displays a complex pattern with evidence of low-lying isomers. Global-minimum searches and extensive theoretical calculations revealed a complicated potential energy surface for B29 with five low-lying isomers, among which the lowest three were shown to contribute to the experimental spectrum. A 3D seashell-like Cs (2, 1A′) isomer, featuring two heptagons on the waist and one octagon at the bottom, is the global minimum for B29, followed by a 2D C1 (3, 1A) isomer with a hexagonal hole and a stingray-shaped 2D Cs (1, 1A′) isomer with a pentagonal hole. However, by taking into account the entropic effects, the stingray-shaped isomer 1 was shown to be the lowest in energy at room temperature and was found to dominate the PES spectrum. Isomers 2 and 3, which have lower electron binding energies, were also found to be present in the experiment. Chemical bonding analyses showed that isomer 1 is an all-boron analogue of benzo[ghi]fluoranthene (C18H10), whereas the borospherene isomer 2 possesses 18π electrons, conforming to the 2(N + 1)2 electron counting rule for spherical aromaticity. For the B29 neutral cluster, the seashell-like borospherene isomer is the global minimum, significantly lower in energy than the stingray-shaped quasi-planar structure.

Graphical abstract: Competition between quasi-planar and cage-like structures in the B29− cluster: photoelectron spectroscopy and ab initio calculations

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Publication details

The article was received on 04 Aug 2016, accepted on 23 Sep 2016 and first published on 23 Sep 2016


Article type: Paper
DOI: 10.1039/C6CP05420J
Citation: Phys. Chem. Chem. Phys., 2016,18, 29147-29155
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    Competition between quasi-planar and cage-like structures in the B29 cluster: photoelectron spectroscopy and ab initio calculations

    H. Li, T. Jian, W. Li, C. Miao, Y. Wang, Q. Chen, X. Luo, K. Wang, H. Zhai, S. Li and L. Wang, Phys. Chem. Chem. Phys., 2016, 18, 29147
    DOI: 10.1039/C6CP05420J

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