title: Photoelectron spectroscopy and ab initio study of the doubly antiaromatic B(6) (2-) dianion in the LiB(6) (-) cluster.
abstract: A metal-boron mixed cluster LiB(6) (-) was produced and characterized by photoelectron spectroscopy and ab initio calculations. A number of electronic transitions were observed and used to compare with theoretical calculations. An extensive search for the global minimum of LiB(6) (-) was carried out via an ab initio genetic algorithm technique. The pyramidal C(2v) ((1)A(1)) molecule was found to be the most stable at all levels of theory. The nearest low-lying isomer was found to be a triplet C(2) ((3)B) structure, 9.2 kcal/mol higher in energy. Comparison of calculated detachment transitions from LiB(6) (-) and the experimental photoelectron spectra confirmed the C(2v) pyramidal global minimum structure. Natural population calculation revealed that LiB(6) (-) is a charge-transfer complex, Li(+)B(6) (2-), in which Li(+) and B(6) (2-) interact in a primarily ionic manner. Analyses of the molecular orbitals and chemical bonding of B(6) (2-) showed that the planar cluster is twofold (pi- and sigma-) antiaromatic, which can be viewed as the fusion of two aromatic B(3) (-) units.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA.
authors.forename: Anastassia N
authors.initials: AN
authors.lastname: Alexandrova
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Boldyrev
authors.forename: Hua-Jin
authors.initials: HJ
authors.lastname: Zhai
authors.forename: Lai-Sheng
authors.initials: LS
authors.lastname: Wang