Theoretical study of the second hyperpolarizabilities of three charged states of pentalene. A consideration of the structure-property correlation for the sensitive second hyperpolarizability

The static second hyperpolarizabilities (γ) for neutral, anion radical and dianion states for a symmetric condensed-ring conjugated system, i.e. pentalene, are calculated by the use of ab initio molecular orbital methods with extended basis sets. The dependence of electron correlation effects on γ is investigated by using the hyperpolarizability density analysis. Remarkable differences in the γ and the characteristics of the spatial contributions of γ densities are observed for different electron correlation results and for different charged states of this system.