Stabilizing carbon-lithium stars†
We have explored in silico the potential energy surfaces of the C5Linn−6 (n = 5, 6, and 7) clusters using the Gradient Embedded Genetic Algorithm (GEGA) and other computational strategies. The most stable forms of C5Li5− and C5Li6 are two carbon chains linked by two lithium atoms in a persistent seven membered ring capped by two Li atoms. The other Li atoms are arrayed on the edge of the seven membered ring. In contrast, the global minimum structure for C5Li7+ is a bicapped star of D5h symmetry. The molecular orbital analysis and computed magnetic field data suggest that electron delocalization, as well as the saturation of the apical positions of the five-membered carbon ring with lithium atoms in C5Li7+ plays a key role in the stabilization of the carbon-lithium star. In fact, the planar star sub-structure for the carbon ring are unstable without the apical caps. This is also what has been found for the Si analogues. The split of the Bindz in its σ- and π-contribution indicates that C5Li7+ is a π-aromatic and σ-nonaromatic system.