Chirality plays an important role in nature. Nanoclusters can also exhibit chiral properties. We report herein a joint experimental and theoretical investigation on the geometric and electronic structures of B 31 − and B 32 − clusters, using photoelectron spectroscopy in combination with first-principles calculations. Two degenerate quasi-planar chiral C 1 enantiomers ( I and II , 1 A) with a central hexagonal vacancy are identified as the global minima of B 31 − . For B 32 − , two degenerate boat-like quasi-planar chiral C 2 structures ( VI and VII , 2 A) with a central hexagonal vacancy are also found as the global minima, with a low-lying chair-like C i B 32 − ( VIII , 2 A u ) also present in the experiment as a minor isomer. The chiral conversions in quasi-planar B 31 − and B 32 − clusters are investigated and relatively low barriers are found due to the high flexibility of these monolayer clusters, which feature multiple delocalized σ and π bonds over buckled molecular surfaces.
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Planar B 41 − and B 42 − clusters with double-hexagonal vacancies
Since the discovery of the B 40 borospherene, research interests have been directed to the structural evolution of even larger boron clusters. An interesting question concerns if the borospherene cages persist in larger boron clusters like the fullerenes. Here we report a photoelectron spectroscopy (PES) and computational study on the structures and bonding of B 41 − and B 42 − , the largest boron clusters characterized experimentally thus far. The PE spectra of both clusters display broad and complicated features, suggesting the existence of multiple low-lying isomers. Global minimum searches for B 41 − reveal three low-lying isomers ( I–III ), which are all related to the planar B 40 − structure. Isomer II ( C s , 1 A′) possessing a double hexagonal vacancy is found to agree well with the experiment, while isomers I ( C s , 3 A′′) and III ( C s , 1 A′) both with a single hexagonal vacancy are also present as minor isomers in the experiment. The potential landscape of B 42 − is found to be much more complicated with numerous low-lying isomers ( VII–XII ). The quasi-planar structure VIII ( C 1 , 2 A) containing a double hexagonal vacancy is found to make major contributions to the observed PE spectrum of B 42 − , while the other low-lying isomers may also be present to give rise to a complicated spectral pattern. Chemical bonding analyses show isomer II of B 41 − ( C s , 1 A′) and isomer VIII of B 42 − ( C 1 , 2 A) are π aromatic, analogous to that in the polycyclic aromatic hydrocarbon C 27 H 13 + ( C 2v , 1 A 1 ). Borospherene cage isomers are also found for both B 41 − and B 42 − in the global minimum searches, but they are much higher energy isomers.
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- Award ID(s):
- 1763380
- NSF-PAR ID:
- 10165548
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 11
- Issue:
- 48
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 23286 to 23295
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C9NR09522E
