A metal-boron mixed cluster, LiB6-, 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 LiB6- was carried out via an ab initio genetic algorithm technique. The pyramidal C2v (1A1) molecule was found to be the most stable at all levels of theory. The nearest low-lying isomer was found to be a triplet C2 (3B) structure, 9.2 kcal/mol higher in energy at the CCSD(T)/6-311+G(2df)//B3LYP/6-311+G* level. Comparison of calculated detachment transitions from LiB6- and the experimental photoelectron spectra confirmed the C2v pyramidal global minimum structure. Natural population calculation revealed that LiB6- is a charge-transfer complex, Li+B62-, in which Li+ and B62- interact in a primarily ionic manner. Analyses of the molecular orbitals and chemical bonding of B62- showed that the planar cluster is two-fold (- and -) antiaromatic, which can be viewed as the fusion of two aromatic B3- units.
Revised: June 14, 2005 |
Published: February 1, 2005
Citation
Alexandrova A.N., A.I. Boldyrev, H.J. Zhai, and L.S. Wang. 2005.Photoelectron Spectroscopy and Ab Initio Study of the Doubly-Antiaromatic B-6(2-) Dianion in the LiB6- Cluster.Journal of Chemical Physics 122, no. 5:Art. No. 054313.PNNL-SA-43762.