title: A photoelectron spectroscopy and ab initio study of the structures and chemical bonding of the B25(-) cluster.
abstract: Photoelectron spectroscopy and ab initio calculations are used to investigate the structures and chemical bonding of the B25(-) cluster. Global minimum searches reveal a dense potential energy landscape with 13 quasi-planar structures within 10 kcal/mol at the CCSD(T)/6-311+G(d) level of theory. Three quasi-planar isomers (I, II, and III) are lowest in energy and nearly degenerate at the CCSD(T) level of theory, with II and III being 0.8 and 0.9 kcal/mol higher, respectively, whereas at two density functional levels of theory isomer III is the lowest in energy (8.4 kcal/mol more stable than I at PBE0/6-311+G(2df) level). Comparison with experimental photoelectron spectroscopic data shows isomer II to be the major contributor while isomers I and III cannot be ruled out as minor contributors to the observed spectrum. Theoretical analyses reveal similar chemical bonding in I and II, both involving peripheral 2c-2e B-B σ-bonding and delocalized interior σ- and π-bonding. Isomer III has an interesting elongated ribbon-like structure with a π-bonding pattern analogous to those of dibenzopentalene. The high density of low-lying isomers indicates the complexity of the medium-sized boron clusters; the method dependency of predicting relative energies of the low-lying structures for B25(-) suggests the importance of comparison with experiment in determining the global minima of boron clusters at this size range. The appearance of many low-lying quasi-planar structures containing a hexagonal hole in B25(-) suggests the importance of this structural feature in maintaining planarity of larger boron clusters.
authors: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors: Zachary A
authors: ZA
authors: Piazza
authors: Department of Chemistry & Biochemistry, Utah State University, Logan, Utah 84322, USA.
authors: Ivan A
authors: IA
authors: Popov
authors: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors: Wei-Li
authors: WL
authors: Li
authors: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
authors: Rhitankar
authors: R
authors: Pal
authors: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
authors: Xiao Cheng
authors: XC
authors: Zeng
authors: Department of Chemistry & Biochemistry, Utah State University, Logan, Utah 84322, USA.
authors: Alexander I
authors: AI
authors: Boldyrev
authors: Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
authors: Lai-Sheng
authors: LS
authors: Wang