Journal of Physical Chemistry A, Vol.116, No.12, 3290-3294, 2012
CAl2Be32- and Its Salt Complex LiCAl2Be3-: Anionic Global Minima with Planar Pentacoordinate Carbon
Following the isoelectronic relationship in global minima planar pentacoordinate carbon (ppC) species (cationic CAl5+, neutral CAl4Be, and monoanionic CAl3Be2-), we designed a dianionic ppC species C-2v CAl2Be32- (1a) and its salt complex C-2v LiCAl2Be3- (2a) in this work. In combination with DFT and high-level ab initio calculations (CCSD(T)), the extensive exploration on their potential energy surfaces indicates that they are the global minima. Their kinetic stability was proved by two sets of 100 ps ab initio Born-Oppenheimer molecular dynamic simulations at the B3LYP/6-31+G(d) level. The detailed analyses indicate that the introduction of Li+ into 1a only influences the electrovalent bonding (through changing of the charge distribution) and the sigma aromaticity (through changing of the in-plane ring current), while the structures, the bonding properties, the pi aromaticity, and so forth are almost unchanged. Nevertheless, the MO energy levels, the HOMO-LUMO gaps, and the values of vertical detachment energies (VDEs) all verify that the lithiation significantly improves the stability. We think the ppC dianion 1a is possible to detect directly in the gas-phase experiments, but it can be detected as its salt complex 2a more easily.